jlarkin@highlandsniptechnology.com wrote:
> On Thu, 13 Jan 2022 11:16:32 -0500, Phil Hobbs
> <pcdhSpamMeSenseless@electrooptical.net> wrote:
>
>> jlarkin@highlandsniptechnology.com wrote:
>>> On Thu, 13 Jan 2022 06:53:28 -0800 (PST), Three Jeeps
>>> <jjhudak4@gmail.com> wrote:
>>>
>>>> On Wednesday, January 12, 2022 at 10:57:56 PM UTC-5,
>>>> jla...@highlandsniptechnology.com wrote:
>>>>> On Wed, 12 Jan 2022 14:33:48 -0800 (PST), Lasse Langwadt
>>>>> Christensen <lang...@fonz.dk> wrote:
>>>>>
>>>>>> onsdag den 12. januar 2022 kl. 23.20.21 UTC+1 skrev whit3rd:
>>>>>>> On Wednesday, January 12, 2022 at 9:00:21 AM UTC-8, Phil
>>>>>>> Hobbs wrote:
>>>>>>>> Lasse Langwadt Christensen wrote:
>>>>>>>
>>>>>>>>> also much much more expensive than a current sense
>>>>>>>>> amplifier
>>>>>>>>>
>>>>>>>> Of course five LM358As, five dual 2N3906es, one 24V zener
>>>>>>>> dropper, and nine quad pack resistors would do it too.
>>>>>>> True; that's only the first step, though, it just makes a
>>>>>>> ground-referenced signal, and next step is an ADC. Trouble
>>>>>>> is, this is a power signal, with surges expected, so the
>>>>>>> sampling due to an ADC is problematic. Since low-power-using
>>>>>>> modules aren't the most important to get accurate readings
>>>>>>> on, I'd note that an eightpack of VCOs can deliver pulse
>>>>>>> streams that don't ignore any of the abrupt changes in their
>>>>>>> inputs, and at the ground-referenced end it just takes
>>>>>>> counter inputs to digitize the averages over any convenient
>>>>>>> period. Ten kilohertz center frequency, half-second average
>>>>>>> period, beats the precision of a 1% shunt resistor. Total the
>>>>>>> counts to get that ninth number...
>>>>>>>
>>>>>>> A bunch of TLC555 with the INAxxx current doing the capacitor
>>>>>>> charge is the general scheme. You'd want the capacitors
>>>>>>> accurate, and/or adjust counter gate times after calibration,
>>>>>>> and a regulated Vdd for the '555.
>>>>>>>
>>>>>>> Less elaborate, capacitors in parallel with the low-end
>>>>>>> receive resistors to do averaging.
>>>>>>
>>>>>> the Zynq ADC is 1MSPS ...
>>>>> And kinda nasty. But we can scan fast and do a bit of signal
>>>>> averaging in the FPGA. I only need the current measurements every
>>>>> millisecond, to do my shutdown protection logic.
>>>>>
>>>>> Exponential smoothing (1st order lowpass) is easy
>>>>>
>>>>> Vout = Vout + (Vin-Vout) * K with smallish K
>>>>>
>>>>> but my FPGA kids will probably want to do something fancier. --
>>>>>
>>>>> I yam what I yam - Popeye
>>>> For situations like this I tend to like using a simple moving
>>>> average filter with the window being variable. If so inclined,
>>>> could be made adaptive. First or second order biquads can also be
>>>> effective. I usually chose direct form one implementations
>>>
>>> I'm fond of making digital filters out of exponential lags or
>>> integrators, starting with a classic analog filter and essentially
>>> Spicing it inside the FPGA or uP. My fpga folk really don't like
>>> that for some reason. Not enough Zs or something.
>>>
>>> They like filters that have a constant of integration in the output,
>>> and assume that nothing ever goes wrong to make it nonzero. A sinc3
>>> filter terrifies me.
>>
>> Recursive filters can exhibit limit cycles, though. For a simple
>> example, if you put a step function into a one-pole IIR lowpass
>> implemented in fixed point, with a decrement of 0.01 (say), it will get
>> stuck somewhere around 50 units away from the 'true' value. That's DC,
>> but it's still a limit cycle. Fancier filters can have AC limit cycles.
>>
>> Cheers
>>
>> Phil Hobbs
>
> If you do the exponential smoothing equation with K=0.01, in 32 bit
> scaled integer math, it works fine.

But Vout - Vin doesn't decay all the way to zero. With lots of bits and
intelligent scaling, you may not care, of course.

>
> In really dinky machines, the trick is to do
>
> Out = Out + (In-Out)/2^n
>
> which is just a right shift.

Sure.

Cheers

Phil Hobbs

--
Dr Philip C D Hobbs
Principal Consultant
ElectroOptical Innovations LLC / Hobbs ElectroOptics
Optics, Electro-optics, Photonics, Analog Electronics
Briarcliff Manor NY 10510

http://electrooptical.net
http://hobbs-eo.com

On Thu, 13 Jan 2022 09:15:01 -0800 (PST), Lasse Langwadt Christensen
<langwadt@fonz.dk> wrote:

>torsdag den 13. januar 2022 kl. 17.49.33 UTC+1 skrev jla...@highlandsniptechnology.com:
>> On Thu, 13 Jan 2022 11:26:28 -0500, Phil Hobbs
>> <pcdhSpamM...@electrooptical.net> wrote:
>>
>> >John Larkin wrote:
>> >> On Wed, 12 Jan 2022 21:00:23 +0100, Klaus Vestergaard Kragelund
>> >> <klau...@hotmail.com> wrote:
>> >>
>> >>> On 11/01/2022 17.49, jla...@highlandsniptechnology.com wrote:
>> >>>> On Tue, 11 Jan 2022 16:35:10 +0000, l...@poppyrecords.invalid.invalid
>> >>>> (Liz Tuddenham) wrote:
>> >>>>
>> >>>>> <jla...@highlandsniptechnology.com> wrote:
>> >>>>>
>> >>>>>> We'll have a 48 volt, 20 amp power supply that feeds eight plug-in
>> >>>>>> modular load boards. We want to measure all 9 currents so that we can
>> >>>>>> do some sorts of intelligent cutoffs if the eight boards threaten to
>> >>>>>> cave in the big supply.
>> >>>>>>
>> >>>>>> So we want nine mediocre-accuracy unipolar high-side current sensors
>> >>>>>> so we can digitize the currents with a grounded mux/adc.
>> >>>>>>
>> >>>>>> Does anyone have a favorite but cheap high-side current sense IC?
>> >>>>>>
>> >>>>>> We can add shunts, or I guess it could be some Hall thing.
>> >>>>>
>> >>>>> Current mirror using pairs of high voltage PNP transistors?
>> >>>>
>> >>>> I just posted something like that. It should be good enough. If the
>> >>>> voltage drop across Q2 is pitched a little high, so there is a little
>> >>>> positive measurement offset, we can math that out.
>> >>>>
>> >>>>
>> >>>>
>> >>> A single current sense amp, but switched to the different sense
>> >>> resistors with a 50V ana mux. Syncronized to the ADC sampling
>> >>
>> >> We could mux on the high side, with a cheap 4051 type mux. We'd need a
>> >> highside power supply, just a zener, and some way to translate the mux
>> >> address lines.
>> >>
>> >
>> >I still like an ordinary 36V dual or quad RRO op amp for this, running
>> >off +26ish and ground, with a good quad pack such as an
>> >ACASA1003S1003P100 (100k, 0.1% absolute, 0.05% relative), 37 cents.
>> >
>> >That puts both inputs near +24V with the output near ground. There'll
>> >be a little bit of offset, but nothing major, and since you can switch
>> >off all the loads, you can measure it at POST. A little bit of
>> >intentional imbalance will prevent the output from really going to zero,
>> >so the op amp and ADC will both be on-scale at all times.
>> >
>> >Cheers
>> >
>> >Phil Hobbs
>> I could mux into a single official highside measurement chip. But we'd
>> still need to control the mux without slowing down the scan much.
>>
>> AC couple the mux selects? Or use a fast digital isolator, with
>> highside power.
>>
>> If I can actually buy the highside sensor chips for 80 cents each, we
>> can just use 9 of them.
>
>https://lcsc.com/product-detail/span-style-background-color-ff0-Current-span-Sensing-Amplifiers_Diodes-Incorporated-ZXCT1080E5TA_C151589.html
>
>$0.5803 if you buy 100

Nice. We could buy 1000.

We could do the dual layout to have a stuffing option. That's life
these days.

--

If a man will begin with certainties, he shall end with doubts,
but if he will be content to begin with doubts he shall end in certainties.
Francis Bacon

On Wednesday, January 12, 2022 at 11:13:36 PM UTC-8, bill....@ieee.org wrote:
> On Thursday, January 13, 2022 at 3:52:39 PM UTC+11, Flyguy wrote:

> > > > The AD8479 handles up to 600V common mode. Couple this with a current shunt and you are good to go.
> > > > https://www.analog.com/media/en/technical-documentation/data-sheets/ad8479.pdf
> > > also much much more expensive than a current sense amplifier.
> >
> > Well, you might actually compare prices of a working circuit to the AD8479. I don't think you can.
> Mouser Electronics in Australia sell the AD8479 for $A11.67, so that part is do-able.

Something like LM331 is half the price, and doesn't tie up ADCs, because frequency counting
is already logic-level info. If overhead counts, I've always liked frequency conversion because
it allows the CPU to tailor the resolution and response, with minimal latency at each status
check. Think of a motor-bearing analysis, accumulating the harmonics of the rumble
of rotating machines, for days... a big digital accumulator and phase-locking works great
with voltage-frequency conversion.

On 13/01/2022 18:38, John Larkin wrote:
> On Thu, 13 Jan 2022 09:15:01 -0800 (PST), Lasse Langwadt Christensen
> <langwadt@fonz.dk> wrote:
>
>> torsdag den 13. januar 2022 kl. 17.49.33 UTC+1 skrev jla...@highlandsniptechnology.com:
>>> On Thu, 13 Jan 2022 11:26:28 -0500, Phil Hobbs
>>> <pcdhSpamM...@electrooptical.net> wrote:
>>>
>>>> John Larkin wrote:
>>>>> On Wed, 12 Jan 2022 21:00:23 +0100, Klaus Vestergaard Kragelund
>>>>> <klau...@hotmail.com> wrote:
>>>>>
>>>>>> On 11/01/2022 17.49, jla...@highlandsniptechnology.com wrote:
>>>>>>> On Tue, 11 Jan 2022 16:35:10 +0000, l...@poppyrecords.invalid.invalid
>>>>>>> (Liz Tuddenham) wrote:
>>>>>>>
>>>>>>>> <jla...@highlandsniptechnology.com> wrote:
>>>>>>>>
>>>>>>>>> We'll have a 48 volt, 20 amp power supply that feeds eight plug-in
>>>>>>>>> modular load boards. We want to measure all 9 currents so that we can
>>>>>>>>> do some sorts of intelligent cutoffs if the eight boards threaten to
>>>>>>>>> cave in the big supply.
>>>>>>>>>
>>>>>>>>> So we want nine mediocre-accuracy unipolar high-side current sensors
>>>>>>>>> so we can digitize the currents with a grounded mux/adc.
>>>>>>>>>
>>>>>>>>> Does anyone have a favorite but cheap high-side current sense IC?
>>>>>>>>>
>>>>>>>>> We can add shunts, or I guess it could be some Hall thing.
>>>>>>>>
>>>>>>>> Current mirror using pairs of high voltage PNP transistors?
>>>>>>>
>>>>>>> I just posted something like that. It should be good enough. If the
>>>>>>> voltage drop across Q2 is pitched a little high, so there is a little
>>>>>>> positive measurement offset, we can math that out.
>>>>>>>
>>>>>>>
>>>>>>>
>>>>>> A single current sense amp, but switched to the different sense
>>>>>> resistors with a 50V ana mux. Syncronized to the ADC sampling
>>>>>
>>>>> We could mux on the high side, with a cheap 4051 type mux. We'd need a
>>>>> highside power supply, just a zener, and some way to translate the mux
>>>>> address lines.
>>>>>
>>>>
>>>> I still like an ordinary 36V dual or quad RRO op amp for this, running
>>>> off +26ish and ground, with a good quad pack such as an
>>>> ACASA1003S1003P100 (100k, 0.1% absolute, 0.05% relative), 37 cents.
>>>>
>>>> That puts both inputs near +24V with the output near ground. There'll
>>>> be a little bit of offset, but nothing major, and since you can switch
>>>> off all the loads, you can measure it at POST. A little bit of
>>>> intentional imbalance will prevent the output from really going to zero,
>>>> so the op amp and ADC will both be on-scale at all times.
>>>>
>>>> Cheers
>>>>
>>>> Phil Hobbs
>>> I could mux into a single official highside measurement chip. But we'd
>>> still need to control the mux without slowing down the scan much.
>>>
>>> AC couple the mux selects? Or use a fast digital isolator, with
>>> highside power.
>>>
>>> If I can actually buy the highside sensor chips for 80 cents each, we
>>> can just use 9 of them.
>>
>> https://lcsc.com/product-detail/span-style-background-color-ff0-Current-span-Sensing-Amplifiers_Diodes-Incorporated-ZXCT1080E5TA_C151589.html
>>
>> $0.5803 if you buy 100
>
> Nice. We could buy 1000.
>
> We could do the dual layout to have a stuffing option. That's life
> these days.
>

Yes, I suggested the related ZXCT1084 up thread a while back.

If you're in the mood to mux then you could take your 2xPNP current
mirrors and parallel all the measuring collectors into one resistor/ADC
and selectively enable each mirror with a HV open collector driver
(thinking old school ULNxxxx or discretes) ?

piglet

On 14/01/2022 07:45, piglet wrote:
> On 13/01/2022 18:38, John Larkin wrote:
>> On Thu, 13 Jan 2022 09:15:01 -0800 (PST), Lasse Langwadt Christensen
>> <langwadt@fonz.dk> wrote:
>>
>>> torsdag den 13. januar 2022 kl. 17.49.33 UTC+1 skrev
>>> jla...@highlandsniptechnology.com:
>>>> On Thu, 13 Jan 2022 11:26:28 -0500, Phil Hobbs
>>>> <pcdhSpamM...@electrooptical.net> wrote:
>>>>
>>>>> John Larkin wrote:
>>>>>> On Wed, 12 Jan 2022 21:00:23 +0100, Klaus Vestergaard Kragelund
>>>>>> <klau...@hotmail.com> wrote:
>>>>>>
>>>>>>> On 11/01/2022 17.49, jla...@highlandsniptechnology.com wrote:
>>>>>>>> On Tue, 11 Jan 2022 16:35:10 +0000,
>>>>>>>> l...@poppyrecords.invalid.invalid
>>>>>>>> (Liz Tuddenham) wrote:
>>>>>>>>
>>>>>>>>> <jla...@highlandsniptechnology.com> wrote:
>>>>>>>>>
>>>>>>>>>> We'll have a 48 volt, 20 amp power supply that feeds eight
>>>>>>>>>> plug-in
>>>>>>>>>> modular load boards. We want to measure all 9 currents so that
>>>>>>>>>> we can
>>>>>>>>>> do some sorts of intelligent cutoffs if the eight boards
>>>>>>>>>> threaten to
>>>>>>>>>> cave in the big supply.
>>>>>>>>>>
>>>>>>>>>> So we want nine mediocre-accuracy unipolar high-side current
>>>>>>>>>> sensors
>>>>>>>>>> so we can digitize the currents with a grounded mux/adc.
>>>>>>>>>>
>>>>>>>>>> Does anyone have a favorite but cheap high-side current sense IC?
>>>>>>>>>>
>>>>>>>>>> We can add shunts, or I guess it could be some Hall thing.
>>>>>>>>>
>>>>>>>>> Current mirror using pairs of high voltage PNP transistors?
>>>>>>>>
>>>>>>>> I just posted something like that. It should be good enough. If the
>>>>>>>> voltage drop across Q2 is pitched a little high, so there is a
>>>>>>>> little
>>>>>>>> positive measurement offset, we can math that out.
>>>>>>>>
>>>>>>>>
>>>>>>>>
>>>>>>> A single current sense amp, but switched to the different sense
>>>>>>> resistors with a 50V ana mux. Syncronized to the ADC sampling
>>>>>>
>>>>>> We could mux on the high side, with a cheap 4051 type mux. We'd
>>>>>> need a
>>>>>> highside power supply, just a zener, and some way to translate the
>>>>>> mux
>>>>>> address lines.
>>>>>>
>>>>>
>>>>> I still like an ordinary 36V dual or quad RRO op amp for this, running
>>>>> off +26ish and ground, with a good quad pack such as an
>>>>> ACASA1003S1003P100 (100k, 0.1% absolute, 0.05% relative), 37 cents.
>>>>>
>>>>> That puts both inputs near +24V with the output near ground. There'll
>>>>> be a little bit of offset, but nothing major, and since you can switch
>>>>> off all the loads, you can measure it at POST. A little bit of
>>>>> intentional imbalance will prevent the output from really going to
>>>>> zero,
>>>>> so the op amp and ADC will both be on-scale at all times.
>>>>>
>>>>> Cheers
>>>>>
>>>>> Phil Hobbs
>>>> I could mux into a single official highside measurement chip. But we'd
>>>> still need to control the mux without slowing down the scan much.
>>>>
>>>> AC couple the mux selects? Or use a fast digital isolator, with
>>>> highside power.
>>>>
>>>> If I can actually buy the highside sensor chips for 80 cents each, we
>>>> can just use 9 of them.
>>>
>>> https://lcsc.com/product-detail/span-style-background-color-ff0-Current-span-Sensing-Amplifiers_Diodes-Incorporated-ZXCT1080E5TA_C151589.html
>>>
>>>
>>> $0.5803 if you buy 100
>>
>> Nice. We could buy 1000.
>>
>> We could do the dual layout to have a stuffing option. That's life
>> these days.
>>
>
> Yes, I suggested the related ZXCT1084 up thread a while back.
>
> If you're in the mood to mux then you could take your 2xPNP current
> mirrors and parallel all the measuring collectors into one resistor/ADC
> and selectively enable each mirror with a HV open collector driver
> (thinking old school ULNxxxx or discretes) ?
>
> piglet
>
>
>
Maybe you don't even need the open collector enables, a 1/8 or 1/9 drive
should AC couple OK. I guess it depends whether a 60V capacitor is going
to cost more than a 2N7002?

piglet

On Friday, January 14, 2022 at 9:41:59 AM UTC+11, whit3rd wrote:
> On Wednesday, January 12, 2022 at 11:13:36 PM UTC-8, bill....@ieee.org wrote:
> > On Thursday, January 13, 2022 at 3:52:39 PM UTC+11, Flyguy wrote:
>
> > > > > The AD8479 handles up to 600V common mode. Couple this with a current shunt and you are good to go.
> > > > > https://www.analog.com/media/en/technical-documentation/data-sheets/ad8479.pdf
> > > > also much much more expensive than a current sense amplifier.
> > >
> > > Well, you might actually compare prices of a working circuit to the AD8479. I don't think you can.
> > Mouser Electronics in Australia sell the AD8479 for $A11.67, so that part is do-able.
>
> Something like LM331 is half the price, and doesn't tie up ADCs, because frequency counting
> is already logic-level info. If overhead counts, I've always liked frequency conversion because
> it allows the CPU to tailor the resolution and response, with minimal latency at each status
> check. Think of a motor-bearing analysis, accumulating the harmonics of the rumble
> of rotating machines, for days... a big digital accumulator and phase-locking works great
> with voltage-frequency conversion.

Me too. But the charm of the AD8479 is in the four closely matched resistors.

Getting precisely calibrated frequency generators depends on getting precisely calibrated reactive components as well as resistors, so it is piling Pelion upon Ossa.

Precision resistors aren't cheap, but you can buy them. Equally precise capacitors don't exist. Precision inductors are even less precise. You can get stable parts, and calibrate them, but it's a good idea to recalibrate frequently and automatically.

--
Bill Sloman, Sydney

On Friday, January 14, 2022 at 7:05:45 PM UTC-8, bill....@ieee.org wrote:
> On Friday, January 14, 2022 at 9:41:59 AM UTC+11, whit3rd wrote:
> > On Wednesday, January 12, 2022 at 11:13:36 PM UTC-8, bill....@ieee.org wrote:

> > > Mouser Electronics in Australia sell the AD8479 for $A11.67, so that part is do-able.
> >
> > Something like LM331 is half the price, and doesn't tie up ADCs, because frequency counting
> > is already logic-level info. If overhead counts, I've always liked frequency conversion...

> Me too. But the charm of the AD8479 is in the four closely matched resistors.
>
> Getting precisely calibrated frequency generators depends on getting precisely calibrated reactive components as well as resistors, so it is piling Pelion upon Ossa.

The frequency generation is driven by the sensed signal, but the AD8479 and its ilk
use 100:1(?) pre-attenuation and that requires roughly 100x the precision of
those matched components. Only the 3 -terminal current monitor chips
like ZXCT1009F are actually amplifying straight off the sense resistor.

1% capacitors are plenty good enough (unless a 1 kW power supply cannot
be derated to 990W plus/minus 10W). For the AD8479 gain/offset, you
need resistors better than that, .01% or so.

> Precision resistors aren't cheap, but you can buy them. Equally precise capacitors don't exist.

It's mainly about aging, and for the resistors, also matching a quad. Either can be
calibrated, and neither should drift much. There's some auto-zero instrument amps, just
in case you want extra security.

On 15/01/2022 3:05 am, Anthony William Sloman wrote:
> On Friday, January 14, 2022 at 9:41:59 AM UTC+11, whit3rd wrote:
>> On Wednesday, January 12, 2022 at 11:13:36 PM UTC-8, bill....@ieee.org wrote:
>>> On Thursday, January 13, 2022 at 3:52:39 PM UTC+11, Flyguy wrote:
>>
>>>>>> The AD8479 handles up to 600V common mode. Couple this with a current shunt and you are good to go.
>>>>>> https://www.analog.com/media/en/technical-documentation/data-sheets/ad8479.pdf
>>>>> also much much more expensive than a current sense amplifier.
>>>>
>>>> Well, you might actually compare prices of a working circuit to the AD8479. I don't think you can.
>>> Mouser Electronics in Australia sell the AD8479 for $A11.67, so that part is do-able.
>>
>> Something like LM331 is half the price, and doesn't tie up ADCs, because frequency counting
>> is already logic-level info. If overhead counts, I've always liked frequency conversion because
>> it allows the CPU to tailor the resolution and response, with minimal latency at each status
>> check. Think of a motor-bearing analysis, accumulating the harmonics of the rumble
>> of rotating machines, for days... a big digital accumulator and phase-locking works great
>> with voltage-frequency conversion.
>
> Me too. But the charm of the AD8479 is in the four closely matched resistors.
>
> Getting precisely calibrated frequency generators depends on getting precisely calibrated reactive components as well as resistors, so it is piling Pelion upon Ossa.
>
> Precision resistors aren't cheap, but you can buy them. Equally precise capacitors don't exist. Precision inductors are even less precise. You can get stable parts, and calibrate them, but it's a good idea to recalibrate frequently and automatically.
>

All very true and can be great when precision is needed. However the
OP's need is for a low precision sensor for fault detection not exacting
metrology. And one that has to be simple cheap enough to be replicated
eight times. Since it only operates over a limited lab temperature range
the discrete PNP mirror may well be adequate.

piglet

On 12/01/2022 03.44, jlarkin@highlandsniptechnology.com wrote:
> On Tue, 11 Jan 2022 14:44:57 -0800 (PST), Lasse Langwadt Christensen
> <langwadt@fonz.dk> wrote:
>
>> tirsdag den 11. januar 2022 kl. 23.31.35 UTC+1 skrev John Larkin:
>>> On Tue, 11 Jan 2022 12:12:37 -0800 (PST), Lasse Langwadt Christensen
>>> <lang...@fonz.dk> wrote:
>>>
>>>> tirsdag den 11. januar 2022 kl. 18.09.07 UTC+1 skrev jla...@highlandsniptechnology.com:
>>>>> On Mon, 10 Jan 2022 22:34:08 -0800 (PST), whit3rd <whi...@gmail.com>
>>>>> wrote:
>>>>>> On Monday, January 10, 2022 at 7:26:19 PM UTC-8, jla...@highlandsniptechnology.com wrote:
>>>>>>> We'll have a 48 volt, 20 amp power supply that feeds eight plug-in
>>>>>>> modular load boards. We want to measure all 9 currents ...
>>>>>>
>>>>>> So, is this regulated voltages, nine of 'em, and you want the output currents
>>>>> >from nine low-V regulators, or is it input to the regulators, and is that input somewhere
>>>>>> in the vicinity of 48VDC? Are these nine currents going to include initial
>>>>>> charging of filter capacitors? How big are those capacitors? Are some of the
>>>>>> regulators switchers?
>>>>>>
>>>>>> As for 'intelligent cutoffs', do you want to do that at the high-side? A secondary
>>>>>> low-current power supply grounded at the high rail might be economic, if
>>>>>> you want to have nine sensors and nine cutoffs all near the +48V source.
>>>>> There will be eight user-programmable power supplies, each running off
>>>>> +48, all off a common +48 bus fed from a kilowatt bulk power supply.
>>>>> Users can potentially install modules and program and load the
>>>>> supplies such as to cave in the main source, which would be really
>>>>> ugly. That's against the rules in the manual, but we need to protect
>>>>> things if they do it.
>>>>
>>>> there is quite a few high side load switches with short circuit protection
>>>> and a combined current monitor / error output , but I think most of them
>>>> are limited to a ~24V supply
>>> The c code can shut down supply modules as needed. Each power supply
>>> module has its own FPGA that the main controller can address. There's
>>> no need to actually remove 48v power from the baby boards. The master
>>> controller just needs to know the currents and have some reasonable
>>> rules.
>>
>> check.
>>
>> depending on how good the ADC is, maybe just a resistivity divider on the 48V and after each shunt is good enough?
>>
>>
>>
>>
>
> Looks like we can use the XADC in the Zynq, the main controller FPGA.
> That's a 1-volt full-scale, pretty terrible ADC. The voltage drop
> across a shunt might be 50 mV with a common-mode of 48 volts. So we
> need some sort of high-side amp.
>
Maybe use the idea with the resistive divider, but then don't use the
ADC, use a slope converter for increased precision.
That can be done with one cheap comparator, and a loop from the FPGA/Micro

Add a resistor with known drop, to calibrate

On Monday, January 17, 2022 at 5:59:38 PM UTC-5, Klaus Kragelund wrote:
> On 12/01/2022 03.44, jla...@highlandsniptechnology.com wrote:
> > On Tue, 11 Jan 2022 14:44:57 -0800 (PST), Lasse Langwadt Christensen
> > <lang...@fonz.dk> wrote:
> >
> >> tirsdag den 11. januar 2022 kl. 23.31.35 UTC+1 skrev John Larkin:
> >>> On Tue, 11 Jan 2022 12:12:37 -0800 (PST), Lasse Langwadt Christensen
> >>> <lang...@fonz.dk> wrote:
> >>>
> >>>> tirsdag den 11. januar 2022 kl. 18.09.07 UTC+1 skrev jla...@highlandsniptechnology.com:
> >>>>> On Mon, 10 Jan 2022 22:34:08 -0800 (PST), whit3rd <whi...@gmail.com>
> >>>>> wrote:
> >>>>>> On Monday, January 10, 2022 at 7:26:19 PM UTC-8, jla...@highlandsniptechnology.com wrote:
> >>>>>>> We'll have a 48 volt, 20 amp power supply that feeds eight plug-in
> >>>>>>> modular load boards. We want to measure all 9 currents ...
> >>>>>>
> >>>>>> So, is this regulated voltages, nine of 'em, and you want the output currents
> >>>>> >from nine low-V regulators, or is it input to the regulators, and is that input somewhere
> >>>>>> in the vicinity of 48VDC? Are these nine currents going to include initial
> >>>>>> charging of filter capacitors? How big are those capacitors? Are some of the
> >>>>>> regulators switchers?
> >>>>>>
> >>>>>> As for 'intelligent cutoffs', do you want to do that at the high-side? A secondary
> >>>>>> low-current power supply grounded at the high rail might be economic, if
> >>>>>> you want to have nine sensors and nine cutoffs all near the +48V source.
> >>>>> There will be eight user-programmable power supplies, each running off
> >>>>> +48, all off a common +48 bus fed from a kilowatt bulk power supply.
> >>>>> Users can potentially install modules and program and load the
> >>>>> supplies such as to cave in the main source, which would be really
> >>>>> ugly. That's against the rules in the manual, but we need to protect
> >>>>> things if they do it.
> >>>>
> >>>> there is quite a few high side load switches with short circuit protection
> >>>> and a combined current monitor / error output , but I think most of them
> >>>> are limited to a ~24V supply
> >>> The c code can shut down supply modules as needed. Each power supply
> >>> module has its own FPGA that the main controller can address. There's
> >>> no need to actually remove 48v power from the baby boards. The master
> >>> controller just needs to know the currents and have some reasonable
> >>> rules.
> >>
> >> check.
> >>
> >> depending on how good the ADC is, maybe just a resistivity divider on the 48V and after each shunt is good enough?
> >>
> >>
> >>
> >>
> >
> > Looks like we can use the XADC in the Zynq, the main controller FPGA.
> > That's a 1-volt full-scale, pretty terrible ADC. The voltage drop
> > across a shunt might be 50 mV with a common-mode of 48 volts. So we
> > need some sort of high-side amp.
> >
> Maybe use the idea with the resistive divider, but then don't use the
> ADC, use a slope converter for increased precision.
> That can be done with one cheap comparator, and a loop from the FPGA/Micro
>
> Add a resistor with known drop, to calibrate

If the voltage range is not excessive you can use a differential input on the FPGA as a comparator. If it is excessive you can scale it down.

--

Rick C.

+ Get 1,000 miles of free Supercharging
+ Tesla referral code - https://ts.la/richard11209

On Mon, 17 Jan 2022 23:59:27 +0100, Klaus Vestergaard Kragelund
<klauskvik@hotmail.com> wrote:

>On 12/01/2022 03.44, jlarkin@highlandsniptechnology.com wrote:
>> On Tue, 11 Jan 2022 14:44:57 -0800 (PST), Lasse Langwadt Christensen
>> <langwadt@fonz.dk> wrote:
>>
>>> tirsdag den 11. januar 2022 kl. 23.31.35 UTC+1 skrev John Larkin:
>>>> On Tue, 11 Jan 2022 12:12:37 -0800 (PST), Lasse Langwadt Christensen
>>>> <lang...@fonz.dk> wrote:
>>>>
>>>>> tirsdag den 11. januar 2022 kl. 18.09.07 UTC+1 skrev jla...@highlandsniptechnology.com:
>>>>>> On Mon, 10 Jan 2022 22:34:08 -0800 (PST), whit3rd <whi...@gmail.com>
>>>>>> wrote:
>>>>>>> On Monday, January 10, 2022 at 7:26:19 PM UTC-8, jla...@highlandsniptechnology.com wrote:
>>>>>>>> We'll have a 48 volt, 20 amp power supply that feeds eight plug-in
>>>>>>>> modular load boards. We want to measure all 9 currents ...
>>>>>>>
>>>>>>> So, is this regulated voltages, nine of 'em, and you want the output currents
>>>>>> >from nine low-V regulators, or is it input to the regulators, and is that input somewhere
>>>>>>> in the vicinity of 48VDC? Are these nine currents going to include initial
>>>>>>> charging of filter capacitors? How big are those capacitors? Are some of the
>>>>>>> regulators switchers?
>>>>>>>
>>>>>>> As for 'intelligent cutoffs', do you want to do that at the high-side? A secondary
>>>>>>> low-current power supply grounded at the high rail might be economic, if
>>>>>>> you want to have nine sensors and nine cutoffs all near the +48V source.
>>>>>> There will be eight user-programmable power supplies, each running off
>>>>>> +48, all off a common +48 bus fed from a kilowatt bulk power supply.
>>>>>> Users can potentially install modules and program and load the
>>>>>> supplies such as to cave in the main source, which would be really
>>>>>> ugly. That's against the rules in the manual, but we need to protect
>>>>>> things if they do it.
>>>>>
>>>>> there is quite a few high side load switches with short circuit protection
>>>>> and a combined current monitor / error output , but I think most of them
>>>>> are limited to a ~24V supply
>>>> The c code can shut down supply modules as needed. Each power supply
>>>> module has its own FPGA that the main controller can address. There's
>>>> no need to actually remove 48v power from the baby boards. The master
>>>> controller just needs to know the currents and have some reasonable
>>>> rules.
>>>
>>> check.
>>>
>>> depending on how good the ADC is, maybe just a resistivity divider on the 48V and after each shunt is good enough?
>>>
>>>
>>>
>>>
>>
>> Looks like we can use the XADC in the Zynq, the main controller FPGA.
>> That's a 1-volt full-scale, pretty terrible ADC. The voltage drop
>> across a shunt might be 50 mV with a common-mode of 48 volts. So we
>> need some sort of high-side amp.
>>
>Maybe use the idea with the resistive divider, but then don't use the
>ADC, use a slope converter for increased precision.
>That can be done with one cheap comparator, and a loop from the FPGA/Micro
>
>Add a resistor with known drop, to calibrate

It's fun to design circuits, until some clown sells an IC that does it
all for you cheap. Looks like we'll use INA280, which is available and
costs 80 cents, according to TI.

Digikey wants $3. Digikey has become a scalper.

--

If a man will begin with certainties, he shall end with doubts,
but if he will be content to begin with doubts he shall end in certainties.
Francis Bacon

tirsdag den 18. januar 2022 kl. 20.52.58 UTC+1 skrev John Larkin:
> On Mon, 17 Jan 2022 23:59:27 +0100, Klaus Vestergaard Kragelund
> <klau...@hotmail.com> wrote:
>
> >On 12/01/2022 03.44, jla...@highlandsniptechnology.com wrote:
> >> On Tue, 11 Jan 2022 14:44:57 -0800 (PST), Lasse Langwadt Christensen
> >> <lang...@fonz.dk> wrote:
> >>
> >>> tirsdag den 11. januar 2022 kl. 23.31.35 UTC+1 skrev John Larkin:
> >>>> On Tue, 11 Jan 2022 12:12:37 -0800 (PST), Lasse Langwadt Christensen
> >>>> <lang...@fonz.dk> wrote:
> >>>>
> >>>>> tirsdag den 11. januar 2022 kl. 18.09.07 UTC+1 skrev jla...@highlandsniptechnology.com:
> >>>>>> On Mon, 10 Jan 2022 22:34:08 -0800 (PST), whit3rd <whi...@gmail.com>
> >>>>>> wrote:
> >>>>>>> On Monday, January 10, 2022 at 7:26:19 PM UTC-8, jla...@highlandsniptechnology.com wrote:
> >>>>>>>> We'll have a 48 volt, 20 amp power supply that feeds eight plug-in
> >>>>>>>> modular load boards. We want to measure all 9 currents ...
> >>>>>>>
> >>>>>>> So, is this regulated voltages, nine of 'em, and you want the output currents
> >>>>>> >from nine low-V regulators, or is it input to the regulators, and is that input somewhere
> >>>>>>> in the vicinity of 48VDC? Are these nine currents going to include initial
> >>>>>>> charging of filter capacitors? How big are those capacitors? Are some of the
> >>>>>>> regulators switchers?
> >>>>>>>
> >>>>>>> As for 'intelligent cutoffs', do you want to do that at the high-side? A secondary
> >>>>>>> low-current power supply grounded at the high rail might be economic, if
> >>>>>>> you want to have nine sensors and nine cutoffs all near the +48V source.
> >>>>>> There will be eight user-programmable power supplies, each running off
> >>>>>> +48, all off a common +48 bus fed from a kilowatt bulk power supply.
> >>>>>> Users can potentially install modules and program and load the
> >>>>>> supplies such as to cave in the main source, which would be really
> >>>>>> ugly. That's against the rules in the manual, but we need to protect
> >>>>>> things if they do it.
> >>>>>
> >>>>> there is quite a few high side load switches with short circuit protection
> >>>>> and a combined current monitor / error output , but I think most of them
> >>>>> are limited to a ~24V supply
> >>>> The c code can shut down supply modules as needed. Each power supply
> >>>> module has its own FPGA that the main controller can address. There's
> >>>> no need to actually remove 48v power from the baby boards. The master
> >>>> controller just needs to know the currents and have some reasonable
> >>>> rules.
> >>>
> >>> check.
> >>>
> >>> depending on how good the ADC is, maybe just a resistivity divider on the 48V and after each shunt is good enough?
> >>>
> >>>
> >>>
> >>>
> >>
> >> Looks like we can use the XADC in the Zynq, the main controller FPGA.
> >> That's a 1-volt full-scale, pretty terrible ADC. The voltage drop
> >> across a shunt might be 50 mV with a common-mode of 48 volts. So we
> >> need some sort of high-side amp.
> >>
> >Maybe use the idea with the resistive divider, but then don't use the
> >ADC, use a slope converter for increased precision.
> >That can be done with one cheap comparator, and a loop from the FPGA/Micro
> >
> >Add a resistor with known drop, to calibrate
> It's fun to design circuits, until some clown sells an IC that does it
> all for you cheap. Looks like we'll use INA280, which is available and
> costs 80 cents, according to TI.
>
> Digikey wants $3. Digikey has become a scalper.

or is is just a matter of supply and demand and Digikey is doing you a favor
by discouraging hoarding, so if you really need a part you can get it

On 2022-01-18, John Larkin <jlarkin@highland_atwork_technology.com> wrote:
> On Mon, 17 Jan 2022 23:59:27 +0100, Klaus Vestergaard Kragelund
><klauskvik@hotmail.com> wrote:
>
>>On 12/01/2022 03.44, jlarkin@highlandsniptechnology.com wrote:
>>> On Tue, 11 Jan 2022 14:44:57 -0800 (PST), Lasse Langwadt Christensen
>>> <langwadt@fonz.dk> wrote:
>>>
>>>> tirsdag den 11. januar 2022 kl. 23.31.35 UTC+1 skrev John Larkin:
>>>>> On Tue, 11 Jan 2022 12:12:37 -0800 (PST), Lasse Langwadt Christensen
>>>>> <lang...@fonz.dk> wrote:
>>>>>
>>>>>> tirsdag den 11. januar 2022 kl. 18.09.07 UTC+1 skrev jla...@highlandsniptechnology.com:
>>>>>>> On Mon, 10 Jan 2022 22:34:08 -0800 (PST), whit3rd <whi...@gmail.com>
>>>>>>> wrote:
>>>>>>>> On Monday, January 10, 2022 at 7:26:19 PM UTC-8, jla...@highlandsniptechnology.com wrote:
>>>>>>>>> We'll have a 48 volt, 20 amp power supply that feeds eight plug-in
>>>>>>>>> modular load boards. We want to measure all 9 currents ...
>>>>>>>>
>>>>>>>> So, is this regulated voltages, nine of 'em, and you want the output currents
>>>>>>> >from nine low-V regulators, or is it input to the regulators, and is that input somewhere
>>>>>>>> in the vicinity of 48VDC? Are these nine currents going to include initial
>>>>>>>> charging of filter capacitors? How big are those capacitors? Are some of the
>>>>>>>> regulators switchers?
>>>>>>>>
>>>>>>>> As for 'intelligent cutoffs', do you want to do that at the high-side? A secondary
>>>>>>>> low-current power supply grounded at the high rail might be economic, if
>>>>>>>> you want to have nine sensors and nine cutoffs all near the +48V source.
>>>>>>> There will be eight user-programmable power supplies, each running off
>>>>>>> +48, all off a common +48 bus fed from a kilowatt bulk power supply.
>>>>>>> Users can potentially install modules and program and load the
>>>>>>> supplies such as to cave in the main source, which would be really
>>>>>>> ugly. That's against the rules in the manual, but we need to protect
>>>>>>> things if they do it.
>>>>>>
>>>>>> there is quite a few high side load switches with short circuit protection
>>>>>> and a combined current monitor / error output , but I think most of them
>>>>>> are limited to a ~24V supply
>>>>> The c code can shut down supply modules as needed. Each power supply
>>>>> module has its own FPGA that the main controller can address. There's
>>>>> no need to actually remove 48v power from the baby boards. The master
>>>>> controller just needs to know the currents and have some reasonable
>>>>> rules.
>>>>
>>>> check.
>>>>
>>>> depending on how good the ADC is, maybe just a resistivity divider on the 48V and after each shunt is good enough?
>>>>
>>>>
>>>>
>>>>
>>>
>>> Looks like we can use the XADC in the Zynq, the main controller FPGA.
>>> That's a 1-volt full-scale, pretty terrible ADC. The voltage drop
>>> across a shunt might be 50 mV with a common-mode of 48 volts. So we
>>> need some sort of high-side amp.
>>>
>>Maybe use the idea with the resistive divider, but then don't use the
>>ADC, use a slope converter for increased precision.
>>That can be done with one cheap comparator, and a loop from the FPGA/Micro
>>
>>Add a resistor with known drop, to calibrate
>
> It's fun to design circuits, until some clown sells an IC that does it
> all for you cheap. Looks like we'll use INA280, which is available and
> costs 80 cents, according to TI.
>
> Digikey wants $3. Digikey has become a scalper.

Or at-least an agent for a scalper. They're listing Rochester Electronics
as supplier on some lines (other parts).

sfaik digikey mostly sells to designers, people making large numbers
of devices find their parts elsewhere.

--
Jasen.

On 19/01/2022 09.27, Jasen Betts wrote:
> On 2022-01-18, John Larkin <jlarkin@highland_atwork_technology.com> wrote:
>> On Mon, 17 Jan 2022 23:59:27 +0100, Klaus Vestergaard Kragelund
>> <klauskvik@hotmail.com> wrote:
>>
>>> On 12/01/2022 03.44, jlarkin@highlandsniptechnology.com wrote:
>>>> On Tue, 11 Jan 2022 14:44:57 -0800 (PST), Lasse Langwadt Christensen
>>>> <langwadt@fonz.dk> wrote:
>>>>
>>>>> tirsdag den 11. januar 2022 kl. 23.31.35 UTC+1 skrev John Larkin:
>>>>>> On Tue, 11 Jan 2022 12:12:37 -0800 (PST), Lasse Langwadt Christensen
>>>>>> <lang...@fonz.dk> wrote:
>>>>>>
>>>>>>> tirsdag den 11. januar 2022 kl. 18.09.07 UTC+1 skrev jla...@highlandsniptechnology.com:
>>>>>>>> On Mon, 10 Jan 2022 22:34:08 -0800 (PST), whit3rd <whi...@gmail.com>
>>>>>>>> wrote:
>>>>>>>>> On Monday, January 10, 2022 at 7:26:19 PM UTC-8, jla...@highlandsniptechnology.com wrote:
>>>>>>>>>> We'll have a 48 volt, 20 amp power supply that feeds eight plug-in
>>>>>>>>>> modular load boards. We want to measure all 9 currents ...
>>>>>>>>>
>>>>>>>>> So, is this regulated voltages, nine of 'em, and you want the output currents
>>>>>>>> >from nine low-V regulators, or is it input to the regulators, and is that input somewhere
>>>>>>>>> in the vicinity of 48VDC? Are these nine currents going to include initial
>>>>>>>>> charging of filter capacitors? How big are those capacitors? Are some of the
>>>>>>>>> regulators switchers?
>>>>>>>>>
>>>>>>>>> As for 'intelligent cutoffs', do you want to do that at the high-side? A secondary
>>>>>>>>> low-current power supply grounded at the high rail might be economic, if
>>>>>>>>> you want to have nine sensors and nine cutoffs all near the +48V source.
>>>>>>>> There will be eight user-programmable power supplies, each running off
>>>>>>>> +48, all off a common +48 bus fed from a kilowatt bulk power supply.
>>>>>>>> Users can potentially install modules and program and load the
>>>>>>>> supplies such as to cave in the main source, which would be really
>>>>>>>> ugly. That's against the rules in the manual, but we need to protect
>>>>>>>> things if they do it.
>>>>>>>
>>>>>>> there is quite a few high side load switches with short circuit protection
>>>>>>> and a combined current monitor / error output , but I think most of them
>>>>>>> are limited to a ~24V supply
>>>>>> The c code can shut down supply modules as needed. Each power supply
>>>>>> module has its own FPGA that the main controller can address. There's
>>>>>> no need to actually remove 48v power from the baby boards. The master
>>>>>> controller just needs to know the currents and have some reasonable
>>>>>> rules.
>>>>>
>>>>> check.
>>>>>
>>>>> depending on how good the ADC is, maybe just a resistivity divider on the 48V and after each shunt is good enough?
>>>>>
>>>>>
>>>>>
>>>>>
>>>>
>>>> Looks like we can use the XADC in the Zynq, the main controller FPGA.
>>>> That's a 1-volt full-scale, pretty terrible ADC. The voltage drop
>>>> across a shunt might be 50 mV with a common-mode of 48 volts. So we
>>>> need some sort of high-side amp.
>>>>
>>> Maybe use the idea with the resistive divider, but then don't use the
>>> ADC, use a slope converter for increased precision.
>>> That can be done with one cheap comparator, and a loop from the FPGA/Micro
>>>
>>> Add a resistor with known drop, to calibrate
>>
>> It's fun to design circuits, until some clown sells an IC that does it
>> all for you cheap. Looks like we'll use INA280, which is available and
>> costs 80 cents, according to TI.
>>
>> Digikey wants $3. Digikey has become a scalper.
>
> Or at-least an agent for a scalper. They're listing Rochester Electronics
> as supplier on some lines (other parts).
>
> sfaik digikey mostly sells to designers, people making large numbers
> of devices find their parts elsewhere.
>
Yes, nobody buys in scale from Digikey

80cents is expensive in my world, but then again I also come from a
business where qty products sold was counted in millions

On Wed, 19 Jan 2022 13:22:38 +0100, Klaus Vestergaard Kragelund
<klauskvik@hotmail.com> wrote:

>On 19/01/2022 09.27, Jasen Betts wrote:
>> On 2022-01-18, John Larkin <jlarkin@highland_atwork_technology.com> wrote:
>>> On Mon, 17 Jan 2022 23:59:27 +0100, Klaus Vestergaard Kragelund
>>> <klauskvik@hotmail.com> wrote:
>>>
>>>> On 12/01/2022 03.44, jlarkin@highlandsniptechnology.com wrote:
>>>>> On Tue, 11 Jan 2022 14:44:57 -0800 (PST), Lasse Langwadt Christensen
>>>>> <langwadt@fonz.dk> wrote:
>>>>>
>>>>>> tirsdag den 11. januar 2022 kl. 23.31.35 UTC+1 skrev John Larkin:
>>>>>>> On Tue, 11 Jan 2022 12:12:37 -0800 (PST), Lasse Langwadt Christensen
>>>>>>> <lang...@fonz.dk> wrote:
>>>>>>>
>>>>>>>> tirsdag den 11. januar 2022 kl. 18.09.07 UTC+1 skrev jla...@highlandsniptechnology.com:
>>>>>>>>> On Mon, 10 Jan 2022 22:34:08 -0800 (PST), whit3rd <whi...@gmail.com>
>>>>>>>>> wrote:
>>>>>>>>>> On Monday, January 10, 2022 at 7:26:19 PM UTC-8, jla...@highlandsniptechnology.com wrote:
>>>>>>>>>>> We'll have a 48 volt, 20 amp power supply that feeds eight plug-in
>>>>>>>>>>> modular load boards. We want to measure all 9 currents ...
>>>>>>>>>>
>>>>>>>>>> So, is this regulated voltages, nine of 'em, and you want the output currents
>>>>>>>>> >from nine low-V regulators, or is it input to the regulators, and is that input somewhere
>>>>>>>>>> in the vicinity of 48VDC? Are these nine currents going to include initial
>>>>>>>>>> charging of filter capacitors? How big are those capacitors? Are some of the
>>>>>>>>>> regulators switchers?
>>>>>>>>>>
>>>>>>>>>> As for 'intelligent cutoffs', do you want to do that at the high-side? A secondary
>>>>>>>>>> low-current power supply grounded at the high rail might be economic, if
>>>>>>>>>> you want to have nine sensors and nine cutoffs all near the +48V source.
>>>>>>>>> There will be eight user-programmable power supplies, each running off
>>>>>>>>> +48, all off a common +48 bus fed from a kilowatt bulk power supply.
>>>>>>>>> Users can potentially install modules and program and load the
>>>>>>>>> supplies such as to cave in the main source, which would be really
>>>>>>>>> ugly. That's against the rules in the manual, but we need to protect
>>>>>>>>> things if they do it.
>>>>>>>>
>>>>>>>> there is quite a few high side load switches with short circuit protection
>>>>>>>> and a combined current monitor / error output , but I think most of them
>>>>>>>> are limited to a ~24V supply
>>>>>>> The c code can shut down supply modules as needed. Each power supply
>>>>>>> module has its own FPGA that the main controller can address. There's
>>>>>>> no need to actually remove 48v power from the baby boards. The master
>>>>>>> controller just needs to know the currents and have some reasonable
>>>>>>> rules.
>>>>>>
>>>>>> check.
>>>>>>
>>>>>> depending on how good the ADC is, maybe just a resistivity divider on the 48V and after each shunt is good enough?
>>>>>>
>>>>>>
>>>>>>
>>>>>>
>>>>>
>>>>> Looks like we can use the XADC in the Zynq, the main controller FPGA.
>>>>> That's a 1-volt full-scale, pretty terrible ADC. The voltage drop
>>>>> across a shunt might be 50 mV with a common-mode of 48 volts. So we
>>>>> need some sort of high-side amp.
>>>>>
>>>> Maybe use the idea with the resistive divider, but then don't use the
>>>> ADC, use a slope converter for increased precision.
>>>> That can be done with one cheap comparator, and a loop from the FPGA/Micro
>>>>
>>>> Add a resistor with known drop, to calibrate
>>>
>>> It's fun to design circuits, until some clown sells an IC that does it
>>> all for you cheap. Looks like we'll use INA280, which is available and
>>> costs 80 cents, according to TI.
>>>
>>> Digikey wants $3. Digikey has become a scalper.
>>
>> Or at-least an agent for a scalper. They're listing Rochester Electronics
>> as supplier on some lines (other parts).
>>
>> sfaik digikey mostly sells to designers, people making large numbers
>> of devices find their parts elsewhere.
>>
>Yes, nobody buys in scale from Digikey
>
>80cents is expensive in my world, but then again I also come from a
>business where qty products sold was counted in millions

We sell modest volumes of fairly expensive stuff. Parts cost is
roughly 12% of sales price, and people (purchasing, engineering,
manufacturing, testing) are a much bigger cost. Lately, availability
dominates cost.

PCBs and metal cases, both custom, are big costs.

We buy a fair amount from Mouser and Digikey, expecially things like
resistors that cost a fraction of a cent each.

A sales guy, from Arrow or Avnet or one of the biggies, said that
"distributors" don't stock parts much any more, but Mouser and Digikey
do. It looks to me that Digikey at least is trending that way too;
it's hard to tell right now.

--

I yam what I yam - Popeye

Klaus Vestergaard Kragelund wrote:
> On 19/01/2022 09.27, Jasen Betts wrote:
>> On 2022-01-18, John Larkin <jlarkin@highland_atwork_technology.com>
>> wrote:
>>> On Mon, 17 Jan 2022 23:59:27 +0100, Klaus Vestergaard Kragelund
>>> <klauskvik@hotmail.com> wrote:
>>>
>>>> On 12/01/2022 03.44, jlarkin@highlandsniptechnology.com wrote:
>>>>> On Tue, 11 Jan 2022 14:44:57 -0800 (PST), Lasse Langwadt Christensen
>>>>> <langwadt@fonz.dk> wrote:
>>>>>
>>>>>> tirsdag den 11. januar 2022 kl. 23.31.35 UTC+1 skrev John Larkin:
>>>>>>> On Tue, 11 Jan 2022 12:12:37 -0800 (PST), Lasse Langwadt Christensen
>>>>>>> <lang...@fonz.dk> wrote:
>>>>>>>
>>>>>>>> tirsdag den 11. januar 2022 kl. 18.09.07 UTC+1 skrev
>>>>>>>> jla...@highlandsniptechnology.com:
>>>>>>>>> On Mon, 10 Jan 2022 22:34:08 -0800 (PST), whit3rd
>>>>>>>>> <whi...@gmail.com>
>>>>>>>>> wrote:
>>>>>>>>>> On Monday, January 10, 2022 at 7:26:19 PM UTC-8,
>>>>>>>>>> jla...@highlandsniptechnology.com wrote:
>>>>>>>>>>> We'll have a 48 volt, 20 amp power supply that feeds eight
>>>>>>>>>>> plug-in
>>>>>>>>>>> modular load boards. We want to measure all 9 currents ...
>>>>>>>>>>
>>>>>>>>>> So, is this regulated voltages, nine of 'em, and you want the
>>>>>>>>>> output currents
>>>>>>>>> >from nine low-V regulators, or is it input to the regulators,
>>>>>>>>> and is that input somewhere
>>>>>>>>>> in the vicinity of 48VDC? Are these nine currents going to
>>>>>>>>>> include initial
>>>>>>>>>> charging of filter capacitors? How big are those capacitors?
>>>>>>>>>> Are some of the
>>>>>>>>>> regulators switchers?
>>>>>>>>>>
>>>>>>>>>> As for 'intelligent cutoffs', do you want to do that at the
>>>>>>>>>> high-side? A secondary
>>>>>>>>>> low-current power supply grounded at the high rail might be
>>>>>>>>>> economic, if
>>>>>>>>>> you want to have nine sensors and nine cutoffs all near the
>>>>>>>>>> +48V source.
>>>>>>>>> There will be eight user-programmable power supplies, each
>>>>>>>>> running off
>>>>>>>>> +48, all off a common +48 bus fed from a kilowatt bulk power
>>>>>>>>> supply.
>>>>>>>>> Users can potentially install modules and program and load the
>>>>>>>>> supplies such as to cave in the main source, which would be really
>>>>>>>>> ugly. That's against the rules in the manual, but we need to
>>>>>>>>> protect
>>>>>>>>> things if they do it.
>>>>>>>>
>>>>>>>> there is quite a few high side load switches with short circuit
>>>>>>>> protection
>>>>>>>> and a combined current monitor / error output , but I think most
>>>>>>>> of them
>>>>>>>> are limited to a ~24V supply
>>>>>>> The c code can shut down supply modules as needed. Each power supply
>>>>>>> module has its own FPGA that the main controller can address.
>>>>>>> There's
>>>>>>> no need to actually remove 48v power from the baby boards. The
>>>>>>> master
>>>>>>> controller just needs to know the currents and have some reasonable
>>>>>>> rules.
>>>>>>
>>>>>> check.
>>>>>>
>>>>>> depending on how good the ADC is, maybe just a resistivity divider
>>>>>> on the 48V and after each shunt is good enough?
>>>>>>
>>>>>>
>>>>>>
>>>>>>
>>>>>
>>>>> Looks like we can use the XADC in the Zynq, the main controller FPGA.
>>>>> That's a 1-volt full-scale, pretty terrible ADC. The voltage drop
>>>>> across a shunt might be 50 mV with a common-mode of 48 volts. So we
>>>>> need some sort of high-side amp.
>>>>>
>>>> Maybe use the idea with the resistive divider, but then don't use the
>>>> ADC, use a slope converter for increased precision.
>>>> That can be done with one cheap comparator, and a loop from the
>>>> FPGA/Micro
>>>>
>>>> Add a resistor with known drop, to calibrate
>>>
>>> It's fun to design circuits, until some clown sells an IC that does it
>>> all for you cheap. Looks like we'll use INA280, which is available and
>>> costs 80 cents, according to TI.
>>>
>>> Digikey wants $3. Digikey has become a scalper.
>>
>> Or at-least an agent for a scalper.  They're listing Rochester
>> Electronics
>> as supplier on some lines (other parts).
>>
>> sfaik digikey mostly sells to designers, people making large numbers
>> of devices find their parts elsewhere.
>>
> Yes, nobody buys in scale from Digikey

Somebody must--from the Thief River Falls Reginal Airport webpage:

"From FAA-published information gathered in 2012, the Airport
experiences 31,200 aircraft operations per year (takeoffs and landings)
of which 30,000 operations are attributed to general aviation
operations, 1,250 from air carrier commercial service, 2,600 from other
commercial/cargo service, and 100 military operations. Nearly 5,000
passengers (2,500 enplanement boardings) are processed annually from
scheduled airline flights. The Airport has 26 based aircraft, including
3 multi-piston and 3 jet turbine airplanes.

So that's 3750 commercial takeoffs and landings, and a total of 2500
passengers. (The webmaster is apparently a bit arithmetically
challenged, but oh well.)

Since there's not a lot in Thief River Falls except Digikey, one gathers
that _somebody_ must be buying a lot of stuff from them.

>
> 80cents is expensive in my world, but then again I also come from a
> business where qty products sold was counted in millions

Cheers

Phil Hobbs

--
Dr Philip C D Hobbs
Principal Consultant
ElectroOptical Innovations LLC / Hobbs ElectroOptics
Optics, Electro-optics, Photonics, Analog Electronics
Briarcliff Manor NY 10510

http://electrooptical.net
http://hobbs-eo.com

On Wed, 19 Jan 2022 10:59:04 -0500, Phil Hobbs
<pcdhSpamMeSenseless@electrooptical.net> wrote:

>Klaus Vestergaard Kragelund wrote:
>> On 19/01/2022 09.27, Jasen Betts wrote:
>>> On 2022-01-18, John Larkin <jlarkin@highland_atwork_technology.com>
>>> wrote:
>>>> On Mon, 17 Jan 2022 23:59:27 +0100, Klaus Vestergaard Kragelund
>>>> <klauskvik@hotmail.com> wrote:
>>>>
>>>>> On 12/01/2022 03.44, jlarkin@highlandsniptechnology.com wrote:
>>>>>> On Tue, 11 Jan 2022 14:44:57 -0800 (PST), Lasse Langwadt Christensen
>>>>>> <langwadt@fonz.dk> wrote:
>>>>>>
>>>>>>> tirsdag den 11. januar 2022 kl. 23.31.35 UTC+1 skrev John Larkin:
>>>>>>>> On Tue, 11 Jan 2022 12:12:37 -0800 (PST), Lasse Langwadt Christensen
>>>>>>>> <lang...@fonz.dk> wrote:
>>>>>>>>
>>>>>>>>> tirsdag den 11. januar 2022 kl. 18.09.07 UTC+1 skrev
>>>>>>>>> jla...@highlandsniptechnology.com:
>>>>>>>>>> On Mon, 10 Jan 2022 22:34:08 -0800 (PST), whit3rd
>>>>>>>>>> <whi...@gmail.com>
>>>>>>>>>> wrote:
>>>>>>>>>>> On Monday, January 10, 2022 at 7:26:19 PM UTC-8,
>>>>>>>>>>> jla...@highlandsniptechnology.com wrote:
>>>>>>>>>>>> We'll have a 48 volt, 20 amp power supply that feeds eight
>>>>>>>>>>>> plug-in
>>>>>>>>>>>> modular load boards. We want to measure all 9 currents ...
>>>>>>>>>>>
>>>>>>>>>>> So, is this regulated voltages, nine of 'em, and you want the
>>>>>>>>>>> output currents
>>>>>>>>>> >from nine low-V regulators, or is it input to the regulators,
>>>>>>>>>> and is that input somewhere
>>>>>>>>>>> in the vicinity of 48VDC? Are these nine currents going to
>>>>>>>>>>> include initial
>>>>>>>>>>> charging of filter capacitors? How big are those capacitors?
>>>>>>>>>>> Are some of the
>>>>>>>>>>> regulators switchers?
>>>>>>>>>>>
>>>>>>>>>>> As for 'intelligent cutoffs', do you want to do that at the
>>>>>>>>>>> high-side? A secondary
>>>>>>>>>>> low-current power supply grounded at the high rail might be
>>>>>>>>>>> economic, if
>>>>>>>>>>> you want to have nine sensors and nine cutoffs all near the
>>>>>>>>>>> +48V source.
>>>>>>>>>> There will be eight user-programmable power supplies, each
>>>>>>>>>> running off
>>>>>>>>>> +48, all off a common +48 bus fed from a kilowatt bulk power
>>>>>>>>>> supply.
>>>>>>>>>> Users can potentially install modules and program and load the
>>>>>>>>>> supplies such as to cave in the main source, which would be really
>>>>>>>>>> ugly. That's against the rules in the manual, but we need to
>>>>>>>>>> protect
>>>>>>>>>> things if they do it.
>>>>>>>>>
>>>>>>>>> there is quite a few high side load switches with short circuit
>>>>>>>>> protection
>>>>>>>>> and a combined current monitor / error output , but I think most
>>>>>>>>> of them
>>>>>>>>> are limited to a ~24V supply
>>>>>>>> The c code can shut down supply modules as needed. Each power supply
>>>>>>>> module has its own FPGA that the main controller can address.
>>>>>>>> There's
>>>>>>>> no need to actually remove 48v power from the baby boards. The
>>>>>>>> master
>>>>>>>> controller just needs to know the currents and have some reasonable
>>>>>>>> rules.
>>>>>>>
>>>>>>> check.
>>>>>>>
>>>>>>> depending on how good the ADC is, maybe just a resistivity divider
>>>>>>> on the 48V and after each shunt is good enough?
>>>>>>>
>>>>>>>
>>>>>>>
>>>>>>>
>>>>>>
>>>>>> Looks like we can use the XADC in the Zynq, the main controller FPGA.
>>>>>> That's a 1-volt full-scale, pretty terrible ADC. The voltage drop
>>>>>> across a shunt might be 50 mV with a common-mode of 48 volts. So we
>>>>>> need some sort of high-side amp.
>>>>>>
>>>>> Maybe use the idea with the resistive divider, but then don't use the
>>>>> ADC, use a slope converter for increased precision.
>>>>> That can be done with one cheap comparator, and a loop from the
>>>>> FPGA/Micro
>>>>>
>>>>> Add a resistor with known drop, to calibrate
>>>>
>>>> It's fun to design circuits, until some clown sells an IC that does it
>>>> all for you cheap. Looks like we'll use INA280, which is available and
>>>> costs 80 cents, according to TI.
>>>>
>>>> Digikey wants $3. Digikey has become a scalper.
>>>
>>> Or at-least an agent for a scalper.  They're listing Rochester
>>> Electronics
>>> as supplier on some lines (other parts).
>>>
>>> sfaik digikey mostly sells to designers, people making large numbers
>>> of devices find their parts elsewhere.
>>>
>> Yes, nobody buys in scale from Digikey
>
>Somebody must--from the Thief River Falls Reginal Airport webpage:
>
>"From FAA-published information gathered in 2012, the Airport
>experiences 31,200 aircraft operations per year (takeoffs and landings)
>of which 30,000 operations are attributed to general aviation
>operations, 1,250 from air carrier commercial service, 2,600 from other
>commercial/cargo service, and 100 military operations. Nearly 5,000
>passengers (2,500 enplanement boardings) are processed annually from
>scheduled airline flights. The Airport has 26 based aircraft, including
>3 multi-piston and 3 jet turbine airplanes.
>
>So that's 3750 commercial takeoffs and landings, and a total of 2500
>passengers. (The webmaster is apparently a bit arithmetically
>challenged, but oh well.)
>
>Since there's not a lot in Thief River Falls except Digikey, one gathers
>that _somebody_ must be buying a lot of stuff from them.
>
>>
>> 80cents is expensive in my world, but then again I also come from a
>> business where qty products sold was counted in millions
>
>Cheers
>
>Phil Hobbs

We lazy engineers often specify a Digikey part for an initial buy, and
our excellent purchasing lady buys quantities of the same thing
somewhere else, at a much better price.

Digikey has/had a good multi-vendor search engine. It seems to make
less sense lately. A category might for example have 25,000 items, and
selecting a couple of very obvious qualifiers narrows it down to a
few, or none.

Selecting for example a Vcc range gives a huge list of confusing,
overlapping choices.

Or specifying something explicit gets me non-qualifying parts.

Lots of broken links too.

--

I yam what I yam - Popeye

jlarkin@highlandsniptechnology.com wrote:
> On Wed, 19 Jan 2022 10:59:04 -0500, Phil Hobbs
> <pcdhSpamMeSenseless@electrooptical.net> wrote:
>
>> Klaus Vestergaard Kragelund wrote:
>>> On 19/01/2022 09.27, Jasen Betts wrote:
>>>> On 2022-01-18, John Larkin <jlarkin@highland_atwork_technology.com>
>>>> wrote:
>>>>> On Mon, 17 Jan 2022 23:59:27 +0100, Klaus Vestergaard Kragelund
>>>>> <klauskvik@hotmail.com> wrote:
>>>>>
>>>>>> On 12/01/2022 03.44, jlarkin@highlandsniptechnology.com wrote:
>>>>>>> On Tue, 11 Jan 2022 14:44:57 -0800 (PST), Lasse Langwadt Christensen
>>>>>>> <langwadt@fonz.dk> wrote:
>>>>>>>
>>>>>>>> tirsdag den 11. januar 2022 kl. 23.31.35 UTC+1 skrev John Larkin:
>>>>>>>>> On Tue, 11 Jan 2022 12:12:37 -0800 (PST), Lasse Langwadt Christensen
>>>>>>>>> <lang...@fonz.dk> wrote:
>>>>>>>>>
>>>>>>>>>> tirsdag den 11. januar 2022 kl. 18.09.07 UTC+1 skrev
>>>>>>>>>> jla...@highlandsniptechnology.com:
>>>>>>>>>>> On Mon, 10 Jan 2022 22:34:08 -0800 (PST), whit3rd
>>>>>>>>>>> <whi...@gmail.com>
>>>>>>>>>>> wrote:
>>>>>>>>>>>> On Monday, January 10, 2022 at 7:26:19 PM UTC-8,
>>>>>>>>>>>> jla...@highlandsniptechnology.com wrote:
>>>>>>>>>>>>> We'll have a 48 volt, 20 amp power supply that feeds eight
>>>>>>>>>>>>> plug-in
>>>>>>>>>>>>> modular load boards. We want to measure all 9 currents ...
>>>>>>>>>>>>
>>>>>>>>>>>> So, is this regulated voltages, nine of 'em, and you want the
>>>>>>>>>>>> output currents
>>>>>>>>>>> >from nine low-V regulators, or is it input to the regulators,
>>>>>>>>>>> and is that input somewhere
>>>>>>>>>>>> in the vicinity of 48VDC? Are these nine currents going to
>>>>>>>>>>>> include initial
>>>>>>>>>>>> charging of filter capacitors? How big are those capacitors?
>>>>>>>>>>>> Are some of the
>>>>>>>>>>>> regulators switchers?
>>>>>>>>>>>>
>>>>>>>>>>>> As for 'intelligent cutoffs', do you want to do that at the
>>>>>>>>>>>> high-side? A secondary
>>>>>>>>>>>> low-current power supply grounded at the high rail might be
>>>>>>>>>>>> economic, if
>>>>>>>>>>>> you want to have nine sensors and nine cutoffs all near the
>>>>>>>>>>>> +48V source.
>>>>>>>>>>> There will be eight user-programmable power supplies, each
>>>>>>>>>>> running off
>>>>>>>>>>> +48, all off a common +48 bus fed from a kilowatt bulk power
>>>>>>>>>>> supply.
>>>>>>>>>>> Users can potentially install modules and program and load the
>>>>>>>>>>> supplies such as to cave in the main source, which would be really
>>>>>>>>>>> ugly. That's against the rules in the manual, but we need to
>>>>>>>>>>> protect
>>>>>>>>>>> things if they do it.
>>>>>>>>>>
>>>>>>>>>> there is quite a few high side load switches with short circuit
>>>>>>>>>> protection
>>>>>>>>>> and a combined current monitor / error output , but I think most
>>>>>>>>>> of them
>>>>>>>>>> are limited to a ~24V supply
>>>>>>>>> The c code can shut down supply modules as needed. Each power supply
>>>>>>>>> module has its own FPGA that the main controller can address.
>>>>>>>>> There's
>>>>>>>>> no need to actually remove 48v power from the baby boards. The
>>>>>>>>> master
>>>>>>>>> controller just needs to know the currents and have some reasonable
>>>>>>>>> rules.
>>>>>>>>
>>>>>>>> check.
>>>>>>>>
>>>>>>>> depending on how good the ADC is, maybe just a resistivity divider
>>>>>>>> on the 48V and after each shunt is good enough?
>>>>>>>>
>>>>>>>>
>>>>>>>>
>>>>>>>>
>>>>>>>
>>>>>>> Looks like we can use the XADC in the Zynq, the main controller FPGA.
>>>>>>> That's a 1-volt full-scale, pretty terrible ADC. The voltage drop
>>>>>>> across a shunt might be 50 mV with a common-mode of 48 volts. So we
>>>>>>> need some sort of high-side amp.
>>>>>>>
>>>>>> Maybe use the idea with the resistive divider, but then don't use the
>>>>>> ADC, use a slope converter for increased precision.
>>>>>> That can be done with one cheap comparator, and a loop from the
>>>>>> FPGA/Micro
>>>>>>
>>>>>> Add a resistor with known drop, to calibrate
>>>>>
>>>>> It's fun to design circuits, until some clown sells an IC that does it
>>>>> all for you cheap. Looks like we'll use INA280, which is available and
>>>>> costs 80 cents, according to TI.
>>>>>
>>>>> Digikey wants $3. Digikey has become a scalper.
>>>>
>>>> Or at-least an agent for a scalper.  They're listing Rochester
>>>> Electronics
>>>> as supplier on some lines (other parts).
>>>>
>>>> sfaik digikey mostly sells to designers, people making large numbers
>>>> of devices find their parts elsewhere.
>>>>
>>> Yes, nobody buys in scale from Digikey
>>
>> Somebody must--from the Thief River Falls Reginal Airport webpage:
>>
>> "From FAA-published information gathered in 2012, the Airport
>> experiences 31,200 aircraft operations per year (takeoffs and landings)
>> of which 30,000 operations are attributed to general aviation
>> operations, 1,250 from air carrier commercial service, 2,600 from other
>> commercial/cargo service, and 100 military operations. Nearly 5,000
>> passengers (2,500 enplanement boardings) are processed annually from
>> scheduled airline flights. The Airport has 26 based aircraft, including
>> 3 multi-piston and 3 jet turbine airplanes.
>>
>> So that's 3750 commercial takeoffs and landings, and a total of 2500
>> passengers. (The webmaster is apparently a bit arithmetically
>> challenged, but oh well.)
>>
>> Since there's not a lot in Thief River Falls except Digikey, one gathers
>> that _somebody_ must be buying a lot of stuff from them.
>>
>>> 80cents is expensive in my world, but then again I also come from a
>>> business where qty products sold was counted in millions
>>

>
> We lazy engineers often specify a Digikey part for an initial buy, and
> our excellent purchasing lady buys quantities of the same thing
> somewhere else, at a much better price.

Never mess with purchasing ladies--it's almost as stupid as insulting
somebody who's preparing your food. ;)

> Digikey has/had a good multi-vendor search engine. It seems to make
> less sense lately. A category might for example have 25,000 items, and
> selecting a couple of very obvious qualifiers narrows it down to a
> few, or none.
>
> Selecting for example a Vcc range gives a huge list of confusing,
> overlapping choices.

Yeah, their VCC, slew rate, GBW, and 3 dB bandwidth columns are so
broken. They could usefully add a column for total supply voltage--that
would help a good bit all by itself.h

>
> Or specifying something explicit gets me non-qualifying parts.
>
> Lots of broken links too.

On Wed, 19 Jan 2022 13:39:46 -0500, Phil Hobbs
<pcdhSpamMeSenseless@electrooptical.net> wrote:

>jlarkin@highlandsniptechnology.com wrote:
>> On Wed, 19 Jan 2022 10:59:04 -0500, Phil Hobbs
>> <pcdhSpamMeSenseless@electrooptical.net> wrote:
>>
>>> Klaus Vestergaard Kragelund wrote:
>>>> On 19/01/2022 09.27, Jasen Betts wrote:
>>>>> On 2022-01-18, John Larkin <jlarkin@highland_atwork_technology.com>
>>>>> wrote:
>>>>>> On Mon, 17 Jan 2022 23:59:27 +0100, Klaus Vestergaard Kragelund
>>>>>> <klauskvik@hotmail.com> wrote:
>>>>>>
>>>>>>> On 12/01/2022 03.44, jlarkin@highlandsniptechnology.com wrote:
>>>>>>>> On Tue, 11 Jan 2022 14:44:57 -0800 (PST), Lasse Langwadt Christensen
>>>>>>>> <langwadt@fonz.dk> wrote:
>>>>>>>>
>>>>>>>>> tirsdag den 11. januar 2022 kl. 23.31.35 UTC+1 skrev John Larkin:
>>>>>>>>>> On Tue, 11 Jan 2022 12:12:37 -0800 (PST), Lasse Langwadt Christensen
>>>>>>>>>> <lang...@fonz.dk> wrote:
>>>>>>>>>>
>>>>>>>>>>> tirsdag den 11. januar 2022 kl. 18.09.07 UTC+1 skrev
>>>>>>>>>>> jla...@highlandsniptechnology.com:
>>>>>>>>>>>> On Mon, 10 Jan 2022 22:34:08 -0800 (PST), whit3rd
>>>>>>>>>>>> <whi...@gmail.com>
>>>>>>>>>>>> wrote:
>>>>>>>>>>>>> On Monday, January 10, 2022 at 7:26:19 PM UTC-8,
>>>>>>>>>>>>> jla...@highlandsniptechnology.com wrote:
>>>>>>>>>>>>>> We'll have a 48 volt, 20 amp power supply that feeds eight
>>>>>>>>>>>>>> plug-in
>>>>>>>>>>>>>> modular load boards. We want to measure all 9 currents ...
>>>>>>>>>>>>>
>>>>>>>>>>>>> So, is this regulated voltages, nine of 'em, and you want the
>>>>>>>>>>>>> output currents
>>>>>>>>>>>> >from nine low-V regulators, or is it input to the regulators,
>>>>>>>>>>>> and is that input somewhere
>>>>>>>>>>>>> in the vicinity of 48VDC? Are these nine currents going to
>>>>>>>>>>>>> include initial
>>>>>>>>>>>>> charging of filter capacitors? How big are those capacitors?
>>>>>>>>>>>>> Are some of the
>>>>>>>>>>>>> regulators switchers?
>>>>>>>>>>>>>
>>>>>>>>>>>>> As for 'intelligent cutoffs', do you want to do that at the
>>>>>>>>>>>>> high-side? A secondary
>>>>>>>>>>>>> low-current power supply grounded at the high rail might be
>>>>>>>>>>>>> economic, if
>>>>>>>>>>>>> you want to have nine sensors and nine cutoffs all near the
>>>>>>>>>>>>> +48V source.
>>>>>>>>>>>> There will be eight user-programmable power supplies, each
>>>>>>>>>>>> running off
>>>>>>>>>>>> +48, all off a common +48 bus fed from a kilowatt bulk power
>>>>>>>>>>>> supply.
>>>>>>>>>>>> Users can potentially install modules and program and load the
>>>>>>>>>>>> supplies such as to cave in the main source, which would be really
>>>>>>>>>>>> ugly. That's against the rules in the manual, but we need to
>>>>>>>>>>>> protect
>>>>>>>>>>>> things if they do it.
>>>>>>>>>>>
>>>>>>>>>>> there is quite a few high side load switches with short circuit
>>>>>>>>>>> protection
>>>>>>>>>>> and a combined current monitor / error output , but I think most
>>>>>>>>>>> of them
>>>>>>>>>>> are limited to a ~24V supply
>>>>>>>>>> The c code can shut down supply modules as needed. Each power supply
>>>>>>>>>> module has its own FPGA that the main controller can address.
>>>>>>>>>> There's
>>>>>>>>>> no need to actually remove 48v power from the baby boards. The
>>>>>>>>>> master
>>>>>>>>>> controller just needs to know the currents and have some reasonable
>>>>>>>>>> rules.
>>>>>>>>>
>>>>>>>>> check.
>>>>>>>>>
>>>>>>>>> depending on how good the ADC is, maybe just a resistivity divider
>>>>>>>>> on the 48V and after each shunt is good enough?
>>>>>>>>>
>>>>>>>>>
>>>>>>>>>
>>>>>>>>>
>>>>>>>>
>>>>>>>> Looks like we can use the XADC in the Zynq, the main controller FPGA.
>>>>>>>> That's a 1-volt full-scale, pretty terrible ADC. The voltage drop
>>>>>>>> across a shunt might be 50 mV with a common-mode of 48 volts. So we
>>>>>>>> need some sort of high-side amp.
>>>>>>>>
>>>>>>> Maybe use the idea with the resistive divider, but then don't use the
>>>>>>> ADC, use a slope converter for increased precision.
>>>>>>> That can be done with one cheap comparator, and a loop from the
>>>>>>> FPGA/Micro
>>>>>>>
>>>>>>> Add a resistor with known drop, to calibrate
>>>>>>
>>>>>> It's fun to design circuits, until some clown sells an IC that does it
>>>>>> all for you cheap. Looks like we'll use INA280, which is available and
>>>>>> costs 80 cents, according to TI.
>>>>>>
>>>>>> Digikey wants $3. Digikey has become a scalper.
>>>>>
>>>>> Or at-least an agent for a scalper.  They're listing Rochester
>>>>> Electronics
>>>>> as supplier on some lines (other parts).
>>>>>
>>>>> sfaik digikey mostly sells to designers, people making large numbers
>>>>> of devices find their parts elsewhere.
>>>>>
>>>> Yes, nobody buys in scale from Digikey
>>>
>>> Somebody must--from the Thief River Falls Reginal Airport webpage:
>>>
>>> "From FAA-published information gathered in 2012, the Airport
>>> experiences 31,200 aircraft operations per year (takeoffs and landings)
>>> of which 30,000 operations are attributed to general aviation
>>> operations, 1,250 from air carrier commercial service, 2,600 from other
>>> commercial/cargo service, and 100 military operations. Nearly 5,000
>>> passengers (2,500 enplanement boardings) are processed annually from
>>> scheduled airline flights. The Airport has 26 based aircraft, including
>>> 3 multi-piston and 3 jet turbine airplanes.
>>>
>>> So that's 3750 commercial takeoffs and landings, and a total of 2500
>>> passengers. (The webmaster is apparently a bit arithmetically
>>> challenged, but oh well.)
>>>
>>> Since there's not a lot in Thief River Falls except Digikey, one gathers
>>> that _somebody_ must be buying a lot of stuff from them.
>>>
>>>> 80cents is expensive in my world, but then again I also come from a
>>>> business where qty products sold was counted in millions
>>>
>
>>
>> We lazy engineers often specify a Digikey part for an initial buy, and
>> our excellent purchasing lady buys quantities of the same thing
>> somewhere else, at a much better price.
>
>Never mess with purchasing ladies--it's almost as stupid as insulting
>somebody who's preparing your food. ;)
>
>> Digikey has/had a good multi-vendor search engine. It seems to make
>> less sense lately. A category might for example have 25,000 items, and
>> selecting a couple of very obvious qualifiers narrows it down to a
>> few, or none.
>>
>> Selecting for example a Vcc range gives a huge list of confusing,
>> overlapping choices.
>
>Yeah, their VCC, slew rate, GBW, and 3 dB bandwidth columns are so
>broken. They could usefully add a column for total supply voltage--that
>would help a good bit all by itself.h
>
>>
>> Or specifying something explicit gets me non-qualifying parts.
>>
>> Lots of broken links too.
>
>Especially Samsung MLCC characteristic sheets. They keep breaking them
>for some reason--you'd think DK would just give up and mirror them.
>
>Cheers
>
>Phil Hobbs

On Wednesday, January 19, 2022 at 10:47:43 AM UTC-5, jla...@highlandsniptechnology.com wrote:
> On Wed, 19 Jan 2022 13:22:38 +0100, Klaus Vestergaard Kragelund
> <klau...@hotmail.com> wrote:
>
> >On 19/01/2022 09.27, Jasen Betts wrote:
> >> On 2022-01-18, John Larkin <jlarkin@highland_atwork_technology.com> wrote:
> >>> On Mon, 17 Jan 2022 23:59:27 +0100, Klaus Vestergaard Kragelund
> >>> <klau...@hotmail.com> wrote:
> >>>
> >>>> On 12/01/2022 03.44, jla...@highlandsniptechnology.com wrote:
> >>>>> On Tue, 11 Jan 2022 14:44:57 -0800 (PST), Lasse Langwadt Christensen
> >>>>> <lang...@fonz.dk> wrote:
> >>>>>
> >>>>>> tirsdag den 11. januar 2022 kl. 23.31.35 UTC+1 skrev John Larkin:
> >>>>>>> On Tue, 11 Jan 2022 12:12:37 -0800 (PST), Lasse Langwadt Christensen
> >>>>>>> <lang...@fonz.dk> wrote:
> >>>>>>>
> >>>>>>>> tirsdag den 11. januar 2022 kl. 18.09.07 UTC+1 skrev jla...@highlandsniptechnology.com:
> >>>>>>>>> On Mon, 10 Jan 2022 22:34:08 -0800 (PST), whit3rd <whi...@gmail..com>
> >>>>>>>>> wrote:
> >>>>>>>>>> On Monday, January 10, 2022 at 7:26:19 PM UTC-8, jla...@highlandsniptechnology.com wrote:
> >>>>>>>>>>> We'll have a 48 volt, 20 amp power supply that feeds eight plug-in
> >>>>>>>>>>> modular load boards. We want to measure all 9 currents ...
> >>>>>>>>>>
> >>>>>>>>>> So, is this regulated voltages, nine of 'em, and you want the output currents
> >>>>>>>>> >from nine low-V regulators, or is it input to the regulators, and is that input somewhere
> >>>>>>>>>> in the vicinity of 48VDC? Are these nine currents going to include initial
> >>>>>>>>>> charging of filter capacitors? How big are those capacitors? Are some of the
> >>>>>>>>>> regulators switchers?
> >>>>>>>>>>
> >>>>>>>>>> As for 'intelligent cutoffs', do you want to do that at the high-side? A secondary
> >>>>>>>>>> low-current power supply grounded at the high rail might be economic, if
> >>>>>>>>>> you want to have nine sensors and nine cutoffs all near the +48V source.
> >>>>>>>>> There will be eight user-programmable power supplies, each running off
> >>>>>>>>> +48, all off a common +48 bus fed from a kilowatt bulk power supply.
> >>>>>>>>> Users can potentially install modules and program and load the
> >>>>>>>>> supplies such as to cave in the main source, which would be really
> >>>>>>>>> ugly. That's against the rules in the manual, but we need to protect
> >>>>>>>>> things if they do it.
> >>>>>>>>
> >>>>>>>> there is quite a few high side load switches with short circuit protection
> >>>>>>>> and a combined current monitor / error output , but I think most of them
> >>>>>>>> are limited to a ~24V supply
> >>>>>>> The c code can shut down supply modules as needed. Each power supply
> >>>>>>> module has its own FPGA that the main controller can address. There's
> >>>>>>> no need to actually remove 48v power from the baby boards. The master
> >>>>>>> controller just needs to know the currents and have some reasonable
> >>>>>>> rules.
> >>>>>>
> >>>>>> check.
> >>>>>>
> >>>>>> depending on how good the ADC is, maybe just a resistivity divider on the 48V and after each shunt is good enough?
> >>>>>>
> >>>>>>
> >>>>>>
> >>>>>>
> >>>>>
> >>>>> Looks like we can use the XADC in the Zynq, the main controller FPGA.
> >>>>> That's a 1-volt full-scale, pretty terrible ADC. The voltage drop
> >>>>> across a shunt might be 50 mV with a common-mode of 48 volts. So we
> >>>>> need some sort of high-side amp.
> >>>>>
> >>>> Maybe use the idea with the resistive divider, but then don't use the
> >>>> ADC, use a slope converter for increased precision.
> >>>> That can be done with one cheap comparator, and a loop from the FPGA/Micro
> >>>>
> >>>> Add a resistor with known drop, to calibrate
> >>>
> >>> It's fun to design circuits, until some clown sells an IC that does it
> >>> all for you cheap. Looks like we'll use INA280, which is available and
> >>> costs 80 cents, according to TI.
> >>>
> >>> Digikey wants $3. Digikey has become a scalper.
> >>
> >> Or at-least an agent for a scalper. They're listing Rochester Electronics
> >> as supplier on some lines (other parts).
> >>
> >> sfaik digikey mostly sells to designers, people making large numbers
> >> of devices find their parts elsewhere.
> >>
> >Yes, nobody buys in scale from Digikey
> >
> >80cents is expensive in my world, but then again I also come from a
> >business where qty products sold was counted in millions
> We sell modest volumes of fairly expensive stuff. Parts cost is
> roughly 12% of sales price, and people (purchasing, engineering,
> manufacturing, testing) are a much bigger cost. Lately, availability
> dominates cost.
>
> PCBs and metal cases, both custom, are big costs.
>
> We buy a fair amount from Mouser and Digikey, expecially things like
> resistors that cost a fraction of a cent each.
>
> A sales guy, from Arrow or Avnet or one of the biggies, said that
> "distributors" don't stock parts much any more, but Mouser and Digikey
> do. It looks to me that Digikey at least is trending that way too;
> it's hard to tell right now.
> --
>
> I yam what I yam - Popeye

Interesting, so what is a rule of thumb, from your perspective, to go from parts cost to the manufactured product?
Years ago, a colleague told me that the multiplier was 7-10X, e.g. if there were $10 worth of electronic parts, the cost of the manufactured product would be ~ $70-$100. That was internal costs. Add more for profit. This was for an all-electronic widget. Am sure things would be different if it were electro-mechanical. Lots of other factors could obviously impact this rule of thumb.

Another colleague of mine worked at the Zenith TV electronics engineering department. When given a subsection of a TV receiver to redesign for a new product, they had two over-riding guidelines: 1) minimize parts count, 2) If the cost of parts for the new design increased cost about $0.05 as compared to the old design, he had to go through a justification review. This was back in the 80's so I am sure things have changed a bit. It was, for me, just interesting to hear about this.
j

onsdag den 19. januar 2022 kl. 20.39.07 UTC+1 skrev three_jeeps:
> On Wednesday, January 19, 2022 at 10:47:43 AM UTC-5, jla...@highlandsniptechnology.com wrote:
> > On Wed, 19 Jan 2022 13:22:38 +0100, Klaus Vestergaard Kragelund
> > <klau...@hotmail.com> wrote:
> >
> > >On 19/01/2022 09.27, Jasen Betts wrote:
> > >> On 2022-01-18, John Larkin <jlarkin@highland_atwork_technology.com> wrote:
> > >>> On Mon, 17 Jan 2022 23:59:27 +0100, Klaus Vestergaard Kragelund
> > >>> <klau...@hotmail.com> wrote:
> > >>>
> > >>>> On 12/01/2022 03.44, jla...@highlandsniptechnology.com wrote:
> > >>>>> On Tue, 11 Jan 2022 14:44:57 -0800 (PST), Lasse Langwadt Christensen
> > >>>>> <lang...@fonz.dk> wrote:
> > >>>>>
> > >>>>>> tirsdag den 11. januar 2022 kl. 23.31.35 UTC+1 skrev John Larkin:
> > >>>>>>> On Tue, 11 Jan 2022 12:12:37 -0800 (PST), Lasse Langwadt Christensen
> > >>>>>>> <lang...@fonz.dk> wrote:
> > >>>>>>>
> > >>>>>>>> tirsdag den 11. januar 2022 kl. 18.09.07 UTC+1 skrev jla...@highlandsniptechnology.com:
> > >>>>>>>>> On Mon, 10 Jan 2022 22:34:08 -0800 (PST), whit3rd <whi...@gmail.com>
> > >>>>>>>>> wrote:
> > >>>>>>>>>> On Monday, January 10, 2022 at 7:26:19 PM UTC-8, jla...@highlandsniptechnology.com wrote:
> > >>>>>>>>>>> We'll have a 48 volt, 20 amp power supply that feeds eight plug-in
> > >>>>>>>>>>> modular load boards. We want to measure all 9 currents ...
> > >>>>>>>>>>
> > >>>>>>>>>> So, is this regulated voltages, nine of 'em, and you want the output currents
> > >>>>>>>>> >from nine low-V regulators, or is it input to the regulators, and is that input somewhere
> > >>>>>>>>>> in the vicinity of 48VDC? Are these nine currents going to include initial
> > >>>>>>>>>> charging of filter capacitors? How big are those capacitors? Are some of the
> > >>>>>>>>>> regulators switchers?
> > >>>>>>>>>>
> > >>>>>>>>>> As for 'intelligent cutoffs', do you want to do that at the high-side? A secondary
> > >>>>>>>>>> low-current power supply grounded at the high rail might be economic, if
> > >>>>>>>>>> you want to have nine sensors and nine cutoffs all near the +48V source.
> > >>>>>>>>> There will be eight user-programmable power supplies, each running off
> > >>>>>>>>> +48, all off a common +48 bus fed from a kilowatt bulk power supply.
> > >>>>>>>>> Users can potentially install modules and program and load the
> > >>>>>>>>> supplies such as to cave in the main source, which would be really
> > >>>>>>>>> ugly. That's against the rules in the manual, but we need to protect
> > >>>>>>>>> things if they do it.
> > >>>>>>>>
> > >>>>>>>> there is quite a few high side load switches with short circuit protection
> > >>>>>>>> and a combined current monitor / error output , but I think most of them
> > >>>>>>>> are limited to a ~24V supply
> > >>>>>>> The c code can shut down supply modules as needed. Each power supply
> > >>>>>>> module has its own FPGA that the main controller can address. There's
> > >>>>>>> no need to actually remove 48v power from the baby boards. The master
> > >>>>>>> controller just needs to know the currents and have some reasonable
> > >>>>>>> rules.
> > >>>>>>
> > >>>>>> check.
> > >>>>>>
> > >>>>>> depending on how good the ADC is, maybe just a resistivity divider on the 48V and after each shunt is good enough?
> > >>>>>>
> > >>>>>>
> > >>>>>>
> > >>>>>>
> > >>>>>
> > >>>>> Looks like we can use the XADC in the Zynq, the main controller FPGA.
> > >>>>> That's a 1-volt full-scale, pretty terrible ADC. The voltage drop
> > >>>>> across a shunt might be 50 mV with a common-mode of 48 volts. So we
> > >>>>> need some sort of high-side amp.
> > >>>>>
> > >>>> Maybe use the idea with the resistive divider, but then don't use the
> > >>>> ADC, use a slope converter for increased precision.
> > >>>> That can be done with one cheap comparator, and a loop from the FPGA/Micro
> > >>>>
> > >>>> Add a resistor with known drop, to calibrate
> > >>>
> > >>> It's fun to design circuits, until some clown sells an IC that does it
> > >>> all for you cheap. Looks like we'll use INA280, which is available and
> > >>> costs 80 cents, according to TI.
> > >>>
> > >>> Digikey wants $3. Digikey has become a scalper.
> > >>
> > >> Or at-least an agent for a scalper. They're listing Rochester Electronics
> > >> as supplier on some lines (other parts).
> > >>
> > >> sfaik digikey mostly sells to designers, people making large numbers
> > >> of devices find their parts elsewhere.
> > >>
> > >Yes, nobody buys in scale from Digikey
> > >
> > >80cents is expensive in my world, but then again I also come from a
> > >business where qty products sold was counted in millions
> > We sell modest volumes of fairly expensive stuff. Parts cost is
> > roughly 12% of sales price, and people (purchasing, engineering,
> > manufacturing, testing) are a much bigger cost. Lately, availability
> > dominates cost.
> >
> > PCBs and metal cases, both custom, are big costs.
> >
> > We buy a fair amount from Mouser and Digikey, expecially things like
> > resistors that cost a fraction of a cent each.
> >
> > A sales guy, from Arrow or Avnet or one of the biggies, said that
> > "distributors" don't stock parts much any more, but Mouser and Digikey
> > do. It looks to me that Digikey at least is trending that way too;
> > it's hard to tell right now.
> > --
> >
> > I yam what I yam - Popeye
> Interesting, so what is a rule of thumb, from your perspective, to go from parts cost to the manufactured product?
> Years ago, a colleague told me that the multiplier was 7-10X, e.g. if there were $10 worth of electronic parts, the cost of the manufactured product would be ~ $70-$100. That was internal costs. Add more for profit. This was for an all-electronic widget. Am sure things would be different if it were electro-mechanical. Lots of other factors could obviously impact this rule of thumb.
>
> Another colleague of mine worked at the Zenith TV electronics engineering department. When given a subsection of a TV receiver to redesign for a new product, they had two over-riding guidelines: 1) minimize parts count, 2) If the cost of parts for the new design increased cost about $0.05 as compared to the old design, he had to go through a justification review. This was back in the 80's so I am sure things have changed a bit. It was, for me, just interesting to hear about this.
> j

I've heard of stories of gadgets made in volume so that the monthly cost of something like a few extra resistors could pay an engineers monthly salary

19.01.22 20:47, Lasse Langwadt Christensen wrote:
>onsdag den 19. januar 2022 kl. 20.39.07 UTC+1 skrev three_jeeps:
>> On Wednesday, January 19, 2022 at 10:47:43 AM UTC-5, jla...@highlandsniptechnology.com wrote:
>> > On Wed, 19 Jan 2022 13:22:38 +0100, Klaus Vestergaard Kragelund
>> > <klau...@hotmail.com> wrote:
>> >
>> > >On 19/01/2022 09.27, Jasen Betts wrote:
>> > >> On 2022-01-18, John Larkin <jlarkin@highland_atwork_technology.com> wrote:
>> > >>> On Mon, 17 Jan 2022 23:59:27 +0100, Klaus Vestergaard Kragelund
>> > >>> <klau...@hotmail.com> wrote:
>> > >>>
>> > >>>> On 12/01/2022 03.44, jla...@highlandsniptechnology.com wrote:
>> > >>>>> On Tue, 11 Jan 2022 14:44:57 -0800 (PST), Lasse Langwadt Christensen
>> > >>>>> <lang...@fonz.dk> wrote:
>> > >>>>>
>> > >>>>>> tirsdag den 11. januar 2022 kl. 23.31.35 UTC+1 skrev John Larkin:
>> > >>>>>>> On Tue, 11 Jan 2022 12:12:37 -0800 (PST), Lasse Langwadt Christensen
>> > >>>>>>> <lang...@fonz.dk> wrote:
>> > >>>>>>>
>> > >>>>>>>> tirsdag den 11. januar 2022 kl. 18.09.07 UTC+1 skrev jla...@highlandsniptechnology.com:
>> > >>>>>>>>> On Mon, 10 Jan 2022 22:34:08 -0800 (PST), whit3rd <whi...@gmail.com>
>> > >>>>>>>>> wrote:
>> > >>>>>>>>>> On Monday, January 10, 2022 at 7:26:19 PM UTC-8, jla...@highlandsniptechnology.com wrote:
>> > >>>>>>>>>>> We'll have a 48 volt, 20 amp power supply that feeds eight plug-in
>> > >>>>>>>>>>> modular load boards. We want to measure all 9 currents ...
>> > >>>>>>>>>>
>> > >>>>>>>>>> So, is this regulated voltages, nine of 'em, and you want the output currents
>> > >>>>>>>>> >from nine low-V regulators, or is it input to the regulators, and is that input somewhere
>> > >>>>>>>>>> in the vicinity of 48VDC? Are these nine currents going to include initial
>> > >>>>>>>>>> charging of filter capacitors? How big are those capacitors? Are some of the
>> > >>>>>>>>>> regulators switchers?
>> > >>>>>>>>>>
>> > >>>>>>>>>> As for 'intelligent cutoffs', do you want to do that at the high-side? A secondary
>> > >>>>>>>>>> low-current power supply grounded at the high rail might be economic, if
>> > >>>>>>>>>> you want to have nine sensors and nine cutoffs all near the +48V source.
>> > >>>>>>>>> There will be eight user-programmable power supplies, each running off
>> > >>>>>>>>> +48, all off a common +48 bus fed from a kilowatt bulk power supply.
>> > >>>>>>>>> Users can potentially install modules and program and load the
>> > >>>>>>>>> supplies such as to cave in the main source, which would be really
>> > >>>>>>>>> ugly. That's against the rules in the manual, but we need to protect
>> > >>>>>>>>> things if they do it.
>> > >>>>>>>>
>> > >>>>>>>> there is quite a few high side load switches with short circuit protection
>> > >>>>>>>> and a combined current monitor / error output , but I think most of them
>> > >>>>>>>> are limited to a ~24V supply
>> > >>>>>>> The c code can shut down supply modules as needed. Each power supply
>> > >>>>>>> module has its own FPGA that the main controller can address. There's
>> > >>>>>>> no need to actually remove 48v power from the baby boards. The master
>> > >>>>>>> controller just needs to know the currents and have some reasonable
>> > >>>>>>> rules.
>> > >>>>>>
>> > >>>>>> check.
>> > >>>>>>
>> > >>>>>> depending on how good the ADC is, maybe just a resistivity divider on the 48V and after each shunt is good enough?
>> > >>>>>>
>> > >>>>>>
>> > >>>>>>
>> > >>>>>>
>> > >>>>>
>> > >>>>> Looks like we can use the XADC in the Zynq, the main controller FPGA.
>> > >>>>> That's a 1-volt full-scale, pretty terrible ADC. The voltage drop
>> > >>>>> across a shunt might be 50 mV with a common-mode of 48 volts. So we
>> > >>>>> need some sort of high-side amp.
>> > >>>>>
>> > >>>> Maybe use the idea with the resistive divider, but then don't use the
>> > >>>> ADC, use a slope converter for increased precision.
>> > >>>> That can be done with one cheap comparator, and a loop from the FPGA/Micro
>> > >>>>
>> > >>>> Add a resistor with known drop, to calibrate
>> > >>>
>> > >>> It's fun to design circuits, until some clown sells an IC that does it
>> > >>> all for you cheap. Looks like we'll use INA280, which is available and
>> > >>> costs 80 cents, according to TI.
>> > >>>
>> > >>> Digikey wants $3. Digikey has become a scalper.
>> > >>
>> > >> Or at-least an agent for a scalper. They're listing Rochester Electronics
>> > >> as supplier on some lines (other parts).
>> > >>
>> > >> sfaik digikey mostly sells to designers, people making large numbers
>> > >> of devices find their parts elsewhere.
>> > >>
>> > >Yes, nobody buys in scale from Digikey
>> > >
>> > >80cents is expensive in my world, but then again I also come from a
>> > >business where qty products sold was counted in millions
>> > We sell modest volumes of fairly expensive stuff. Parts cost is
>> > roughly 12% of sales price, and people (purchasing, engineering,
>> > manufacturing, testing) are a much bigger cost. Lately, availability
>> > dominates cost.
>> >
>> > PCBs and metal cases, both custom, are big costs.
>> >
>> > We buy a fair amount from Mouser and Digikey, expecially things like
>> > resistors that cost a fraction of a cent each.
>> >
>> > A sales guy, from Arrow or Avnet or one of the biggies, said that
>> > "distributors" don't stock parts much any more, but Mouser and Digikey
>> > do. It looks to me that Digikey at least is trending that way too;
>> > it's hard to tell right now.
>> > --
>> >
>> > I yam what I yam - Popeye
>> Interesting, so what is a rule of thumb, from your perspective, to go from parts cost to the manufactured product?
>> Years ago, a colleague told me that the multiplier was 7-10X, e.g. if there were $10 worth of electronic parts, the cost of the manufactured product would be ~ $70-$100. That was internal costs. Add more for profit. This was for an all-electronic widget. Am sure things would be different if it were electro-mechanical. Lots of other factors could obviously impact this rule of thumb.
>>
>> Another colleague of mine worked at the Zenith TV electronics engineering department. When given a subsection of a TV receiver to redesign for a new product, they had two over-riding guidelines: 1) minimize parts count, 2) If the cost of parts for the new design increased cost about $0.05 as compared to the old design, he had to go through a justification review. This was back in the 80's so I am sure things have changed a bit. It was, for me, just interesting to hear about this.
>> j
>
>I've heard of stories of gadgets made in volume so that the monthly cost of something like a few extra resistors could pay an engineers monthly salary
>
>
I was the lead innovator on a new product with release in a couple of months

Quantity of 500.000 pcs per month, so a 2 cent cost reduction could pay an engineers salary, not counting all the other overhead

On Wed, 19 Jan 2022 11:39:02 -0800 (PST), three_jeeps
<jjhudak@gmail.com> wrote:

>On Wednesday, January 19, 2022 at 10:47:43 AM UTC-5, jla...@highlandsniptechnology.com wrote:
>> On Wed, 19 Jan 2022 13:22:38 +0100, Klaus Vestergaard Kragelund
>> <klau...@hotmail.com> wrote:
>>
>> >On 19/01/2022 09.27, Jasen Betts wrote:
>> >> On 2022-01-18, John Larkin <jlarkin@highland_atwork_technology.com> wrote:
>> >>> On Mon, 17 Jan 2022 23:59:27 +0100, Klaus Vestergaard Kragelund
>> >>> <klau...@hotmail.com> wrote:
>> >>>
>> >>>> On 12/01/2022 03.44, jla...@highlandsniptechnology.com wrote:
>> >>>>> On Tue, 11 Jan 2022 14:44:57 -0800 (PST), Lasse Langwadt Christensen
>> >>>>> <lang...@fonz.dk> wrote:
>> >>>>>
>> >>>>>> tirsdag den 11. januar 2022 kl. 23.31.35 UTC+1 skrev John Larkin:
>> >>>>>>> On Tue, 11 Jan 2022 12:12:37 -0800 (PST), Lasse Langwadt Christensen
>> >>>>>>> <lang...@fonz.dk> wrote:
>> >>>>>>>
>> >>>>>>>> tirsdag den 11. januar 2022 kl. 18.09.07 UTC+1 skrev jla...@highlandsniptechnology.com:
>> >>>>>>>>> On Mon, 10 Jan 2022 22:34:08 -0800 (PST), whit3rd <whi...@gmail.com>
>> >>>>>>>>> wrote:
>> >>>>>>>>>> On Monday, January 10, 2022 at 7:26:19 PM UTC-8, jla...@highlandsniptechnology.com wrote:
>> >>>>>>>>>>> We'll have a 48 volt, 20 amp power supply that feeds eight plug-in
>> >>>>>>>>>>> modular load boards. We want to measure all 9 currents ...
>> >>>>>>>>>>
>> >>>>>>>>>> So, is this regulated voltages, nine of 'em, and you want the output currents
>> >>>>>>>>> >from nine low-V regulators, or is it input to the regulators, and is that input somewhere
>> >>>>>>>>>> in the vicinity of 48VDC? Are these nine currents going to include initial
>> >>>>>>>>>> charging of filter capacitors? How big are those capacitors? Are some of the
>> >>>>>>>>>> regulators switchers?
>> >>>>>>>>>>
>> >>>>>>>>>> As for 'intelligent cutoffs', do you want to do that at the high-side? A secondary
>> >>>>>>>>>> low-current power supply grounded at the high rail might be economic, if
>> >>>>>>>>>> you want to have nine sensors and nine cutoffs all near the +48V source.
>> >>>>>>>>> There will be eight user-programmable power supplies, each running off
>> >>>>>>>>> +48, all off a common +48 bus fed from a kilowatt bulk power supply.
>> >>>>>>>>> Users can potentially install modules and program and load the
>> >>>>>>>>> supplies such as to cave in the main source, which would be really
>> >>>>>>>>> ugly. That's against the rules in the manual, but we need to protect
>> >>>>>>>>> things if they do it.
>> >>>>>>>>
>> >>>>>>>> there is quite a few high side load switches with short circuit protection
>> >>>>>>>> and a combined current monitor / error output , but I think most of them
>> >>>>>>>> are limited to a ~24V supply
>> >>>>>>> The c code can shut down supply modules as needed. Each power supply
>> >>>>>>> module has its own FPGA that the main controller can address. There's
>> >>>>>>> no need to actually remove 48v power from the baby boards. The master
>> >>>>>>> controller just needs to know the currents and have some reasonable
>> >>>>>>> rules.
>> >>>>>>
>> >>>>>> check.
>> >>>>>>
>> >>>>>> depending on how good the ADC is, maybe just a resistivity divider on the 48V and after each shunt is good enough?
>> >>>>>>
>> >>>>>>
>> >>>>>>
>> >>>>>>
>> >>>>>
>> >>>>> Looks like we can use the XADC in the Zynq, the main controller FPGA.
>> >>>>> That's a 1-volt full-scale, pretty terrible ADC. The voltage drop
>> >>>>> across a shunt might be 50 mV with a common-mode of 48 volts. So we
>> >>>>> need some sort of high-side amp.
>> >>>>>
>> >>>> Maybe use the idea with the resistive divider, but then don't use the
>> >>>> ADC, use a slope converter for increased precision.
>> >>>> That can be done with one cheap comparator, and a loop from the FPGA/Micro
>> >>>>
>> >>>> Add a resistor with known drop, to calibrate
>> >>>
>> >>> It's fun to design circuits, until some clown sells an IC that does it
>> >>> all for you cheap. Looks like we'll use INA280, which is available and
>> >>> costs 80 cents, according to TI.
>> >>>
>> >>> Digikey wants $3. Digikey has become a scalper.
>> >>
>> >> Or at-least an agent for a scalper. They're listing Rochester Electronics
>> >> as supplier on some lines (other parts).
>> >>
>> >> sfaik digikey mostly sells to designers, people making large numbers
>> >> of devices find their parts elsewhere.
>> >>
>> >Yes, nobody buys in scale from Digikey
>> >
>> >80cents is expensive in my world, but then again I also come from a
>> >business where qty products sold was counted in millions
>> We sell modest volumes of fairly expensive stuff. Parts cost is
>> roughly 12% of sales price, and people (purchasing, engineering,
>> manufacturing, testing) are a much bigger cost. Lately, availability
>> dominates cost.
>>
>> PCBs and metal cases, both custom, are big costs.
>>
>> We buy a fair amount from Mouser and Digikey, expecially things like
>> resistors that cost a fraction of a cent each.
>>
>> A sales guy, from Arrow or Avnet or one of the biggies, said that
>> "distributors" don't stock parts much any more, but Mouser and Digikey
>> do. It looks to me that Digikey at least is trending that way too;
>> it's hard to tell right now.
>> --
>>
>> I yam what I yam - Popeye
>
>Interesting, so what is a rule of thumb, from your perspective, to go from parts cost to the manufactured product?

We define "direct cost" as unburdened parts cost plus labor. A selling
price of 3x DC is our lower limit. 6s is better, sometimes 10x is
possible where the value to the customer is high and there is no
competition.

We used to sell NMR gradient amplifiers to Varian/Agilent at maybe 4x
DC. They marked our price up 6x to their customers.

I wonder what a high-end iphone costs Apple.

>Years ago, a colleague told me that the multiplier was 7-10X, e.g. if there were $10 worth of electronic parts, the cost of the manufactured product would be ~ $70-$100. That was internal costs. Add more for profit. This was for an all-electronic widget. Am sure things would be different if it were electro-mechanical. Lots of other factors could obviously impact this rule of thumb.
>
>Another colleague of mine worked at the Zenith TV electronics engineering department. When given a subsection of a TV receiver to redesign for a new product, they had two over-riding guidelines: 1) minimize parts count, 2) If the cost of parts for the new design increased cost about $0.05 as compared to the old design, he had to go through a justification review. This was back in the 80's so I am sure things have changed a bit. It was, for me, just interesting to hear about this.
>j

I get the impression that in high volume, contract manufacturers make
a few per cent over their net costs. They often have contracts that
let the customer audit their actual costs and pay them a few per cent
more.

One of our customers proposed to do that to us. We declined.

--

I yam what I yam - Popeye

On 1/19/2022 1:36 PM, John Larkin wrote:
> On Wed, 19 Jan 2022 13:39:46 -0500, Phil Hobbs
> <pcdhSpamMeSenseless@electrooptical.net> wrote:
>
>> jlarkin@highlandsniptechnology.com wrote:
>>> On Wed, 19 Jan 2022 10:59:04 -0500, Phil Hobbs
>>> <pcdhSpamMeSenseless@electrooptical.net> wrote:
>>>
>>>> Klaus Vestergaard Kragelund wrote:
>>>>> On 19/01/2022 09.27, Jasen Betts wrote:
>>>>>> On 2022-01-18, John Larkin <jlarkin@highland_atwork_technology.com>
>>>>>> wrote:
>>>>>>> On Mon, 17 Jan 2022 23:59:27 +0100, Klaus Vestergaard Kragelund
>>>>>>> <klauskvik@hotmail.com> wrote:
>>>>>>>
>>>>>>>> On 12/01/2022 03.44, jlarkin@highlandsniptechnology.com wrote:
>>>>>>>>> On Tue, 11 Jan 2022 14:44:57 -0800 (PST), Lasse Langwadt Christensen
>>>>>>>>> <langwadt@fonz.dk> wrote:
>>>>>>>>>
>>>>>>>>>> tirsdag den 11. januar 2022 kl. 23.31.35 UTC+1 skrev John Larkin:
>>>>>>>>>>> On Tue, 11 Jan 2022 12:12:37 -0800 (PST), Lasse Langwadt Christensen
>>>>>>>>>>> <lang...@fonz.dk> wrote:
>>>>>>>>>>>
>>>>>>>>>>>> tirsdag den 11. januar 2022 kl. 18.09.07 UTC+1 skrev
>>>>>>>>>>>> jla...@highlandsniptechnology.com:
>>>>>>>>>>>>> On Mon, 10 Jan 2022 22:34:08 -0800 (PST), whit3rd
>>>>>>>>>>>>> <whi...@gmail.com>
>>>>>>>>>>>>> wrote:
>>>>>>>>>>>>>> On Monday, January 10, 2022 at 7:26:19 PM UTC-8,
>>>>>>>>>>>>>> jla...@highlandsniptechnology.com wrote:
>>>>>>>>>>>>>>> We'll have a 48 volt, 20 amp power supply that feeds eight
>>>>>>>>>>>>>>> plug-in
>>>>>>>>>>>>>>> modular load boards. We want to measure all 9 currents ...
>>>>>>>>>>>>>>
>>>>>>>>>>>>>> So, is this regulated voltages, nine of 'em, and you want the
>>>>>>>>>>>>>> output currents
>>>>>>>>>>>>> >from nine low-V regulators, or is it input to the regulators,
>>>>>>>>>>>>> and is that input somewhere
>>>>>>>>>>>>>> in the vicinity of 48VDC? Are these nine currents going to
>>>>>>>>>>>>>> include initial
>>>>>>>>>>>>>> charging of filter capacitors? How big are those capacitors?
>>>>>>>>>>>>>> Are some of the
>>>>>>>>>>>>>> regulators switchers?
>>>>>>>>>>>>>>
>>>>>>>>>>>>>> As for 'intelligent cutoffs', do you want to do that at the
>>>>>>>>>>>>>> high-side? A secondary
>>>>>>>>>>>>>> low-current power supply grounded at the high rail might be
>>>>>>>>>>>>>> economic, if
>>>>>>>>>>>>>> you want to have nine sensors and nine cutoffs all near the
>>>>>>>>>>>>>> +48V source.
>>>>>>>>>>>>> There will be eight user-programmable power supplies, each
>>>>>>>>>>>>> running off
>>>>>>>>>>>>> +48, all off a common +48 bus fed from a kilowatt bulk power
>>>>>>>>>>>>> supply.
>>>>>>>>>>>>> Users can potentially install modules and program and load the
>>>>>>>>>>>>> supplies such as to cave in the main source, which would be really
>>>>>>>>>>>>> ugly. That's against the rules in the manual, but we need to
>>>>>>>>>>>>> protect
>>>>>>>>>>>>> things if they do it.
>>>>>>>>>>>>
>>>>>>>>>>>> there is quite a few high side load switches with short circuit
>>>>>>>>>>>> protection
>>>>>>>>>>>> and a combined current monitor / error output , but I think most
>>>>>>>>>>>> of them
>>>>>>>>>>>> are limited to a ~24V supply
>>>>>>>>>>> The c code can shut down supply modules as needed. Each power supply
>>>>>>>>>>> module has its own FPGA that the main controller can address.
>>>>>>>>>>> There's
>>>>>>>>>>> no need to actually remove 48v power from the baby boards. The
>>>>>>>>>>> master
>>>>>>>>>>> controller just needs to know the currents and have some reasonable
>>>>>>>>>>> rules.
>>>>>>>>>>
>>>>>>>>>> check.
>>>>>>>>>>
>>>>>>>>>> depending on how good the ADC is, maybe just a resistivity divider
>>>>>>>>>> on the 48V and after each shunt is good enough?
>>>>>>>>>>
>>>>>>>>>>
>>>>>>>>>>
>>>>>>>>>>
>>>>>>>>>
>>>>>>>>> Looks like we can use the XADC in the Zynq, the main controller FPGA.
>>>>>>>>> That's a 1-volt full-scale, pretty terrible ADC. The voltage drop
>>>>>>>>> across a shunt might be 50 mV with a common-mode of 48 volts. So we
>>>>>>>>> need some sort of high-side amp.
>>>>>>>>>
>>>>>>>> Maybe use the idea with the resistive divider, but then don't use the
>>>>>>>> ADC, use a slope converter for increased precision.
>>>>>>>> That can be done with one cheap comparator, and a loop from the
>>>>>>>> FPGA/Micro
>>>>>>>>
>>>>>>>> Add a resistor with known drop, to calibrate
>>>>>>>
>>>>>>> It's fun to design circuits, until some clown sells an IC that does it
>>>>>>> all for you cheap. Looks like we'll use INA280, which is available and
>>>>>>> costs 80 cents, according to TI.
>>>>>>>
>>>>>>> Digikey wants $3. Digikey has become a scalper.
>>>>>>
>>>>>> Or at-least an agent for a scalper.  They're listing Rochester
>>>>>> Electronics
>>>>>> as supplier on some lines (other parts).
>>>>>>
>>>>>> sfaik digikey mostly sells to designers, people making large numbers
>>>>>> of devices find their parts elsewhere.
>>>>>>
>>>>> Yes, nobody buys in scale from Digikey
>>>>
>>>> Somebody must--from the Thief River Falls Reginal Airport webpage:
>>>>
>>>> "From FAA-published information gathered in 2012, the Airport
>>>> experiences 31,200 aircraft operations per year (takeoffs and landings)
>>>> of which 30,000 operations are attributed to general aviation
>>>> operations, 1,250 from air carrier commercial service, 2,600 from other
>>>> commercial/cargo service, and 100 military operations. Nearly 5,000
>>>> passengers (2,500 enplanement boardings) are processed annually from
>>>> scheduled airline flights. The Airport has 26 based aircraft, including
>>>> 3 multi-piston and 3 jet turbine airplanes.
>>>>
>>>> So that's 3750 commercial takeoffs and landings, and a total of 2500
>>>> passengers. (The webmaster is apparently a bit arithmetically
>>>> challenged, but oh well.)
>>>>
>>>> Since there's not a lot in Thief River Falls except Digikey, one gathers
>>>> that _somebody_ must be buying a lot of stuff from them.
>>>>
>>>>> 80cents is expensive in my world, but then again I also come from a
>>>>> business where qty products sold was counted in millions
>>>>
>>
>>>
>>> We lazy engineers often specify a Digikey part for an initial buy, and
>>> our excellent purchasing lady buys quantities of the same thing
>>> somewhere else, at a much better price.
>>
>> Never mess with purchasing ladies--it's almost as stupid as insulting
>> somebody who's preparing your food. ;)
>>
>>> Digikey has/had a good multi-vendor search engine. It seems to make
>>> less sense lately. A category might for example have 25,000 items, and
>>> selecting a couple of very obvious qualifiers narrows it down to a
>>> few, or none.
>>>
>>> Selecting for example a Vcc range gives a huge list of confusing,
>>> overlapping choices.
>>
>> Yeah, their VCC, slew rate, GBW, and 3 dB bandwidth columns are so
>> broken. They could usefully add a column for total supply voltage--that
>> would help a good bit all by itself.h
>>
>>>
>>> Or specifying something explicit gets me non-qualifying parts.
>>>
>>> Lots of broken links too.
>>
>> Especially Samsung MLCC characteristic sheets. They keep breaking them
>> for some reason--you'd think DK would just give up and mirror them.
>>
>> Cheers
>>
>> Phil Hobbs
>
> Sometimes they link to a vendor site that requires registration and a
> password and all that nonsense, just to see a data sheet.

torsdag den 20. januar 2022 kl. 03.54.12 UTC+1 skrev jla...@highlandsniptechnology.com:
> On Wed, 19 Jan 2022 11:39:02 -0800 (PST), three_jeeps
> <jjh...@gmail.com> wrote:
>
> >On Wednesday, January 19, 2022 at 10:47:43 AM UTC-5, jla...@highlandsniptechnology.com wrote:
> >> On Wed, 19 Jan 2022 13:22:38 +0100, Klaus Vestergaard Kragelund
> >> <klau...@hotmail.com> wrote:
> >>
> >> >On 19/01/2022 09.27, Jasen Betts wrote:
> >> >> On 2022-01-18, John Larkin <jlarkin@highland_atwork_technology.com> wrote:
> >> >>> On Mon, 17 Jan 2022 23:59:27 +0100, Klaus Vestergaard Kragelund
> >> >>> <klau...@hotmail.com> wrote:
> >> >>>
> >> >>>> On 12/01/2022 03.44, jla...@highlandsniptechnology.com wrote:
> >> >>>>> On Tue, 11 Jan 2022 14:44:57 -0800 (PST), Lasse Langwadt Christensen
> >> >>>>> <lang...@fonz.dk> wrote:
> >> >>>>>
> >> >>>>>> tirsdag den 11. januar 2022 kl. 23.31.35 UTC+1 skrev John Larkin:
> >> >>>>>>> On Tue, 11 Jan 2022 12:12:37 -0800 (PST), Lasse Langwadt Christensen
> >> >>>>>>> <lang...@fonz.dk> wrote:
> >> >>>>>>>
> >> >>>>>>>> tirsdag den 11. januar 2022 kl. 18.09.07 UTC+1 skrev jla...@highlandsniptechnology.com:
> >> >>>>>>>>> On Mon, 10 Jan 2022 22:34:08 -0800 (PST), whit3rd <whi...@gmail.com>
> >> >>>>>>>>> wrote:
> >> >>>>>>>>>> On Monday, January 10, 2022 at 7:26:19 PM UTC-8, jla...@highlandsniptechnology.com wrote:
> >> >>>>>>>>>>> We'll have a 48 volt, 20 amp power supply that feeds eight plug-in
> >> >>>>>>>>>>> modular load boards. We want to measure all 9 currents ...
> >> >>>>>>>>>>
> >> >>>>>>>>>> So, is this regulated voltages, nine of 'em, and you want the output currents
> >> >>>>>>>>> >from nine low-V regulators, or is it input to the regulators, and is that input somewhere
> >> >>>>>>>>>> in the vicinity of 48VDC? Are these nine currents going to include initial
> >> >>>>>>>>>> charging of filter capacitors? How big are those capacitors? Are some of the
> >> >>>>>>>>>> regulators switchers?
> >> >>>>>>>>>>
> >> >>>>>>>>>> As for 'intelligent cutoffs', do you want to do that at the high-side? A secondary
> >> >>>>>>>>>> low-current power supply grounded at the high rail might be economic, if
> >> >>>>>>>>>> you want to have nine sensors and nine cutoffs all near the +48V source.
> >> >>>>>>>>> There will be eight user-programmable power supplies, each running off
> >> >>>>>>>>> +48, all off a common +48 bus fed from a kilowatt bulk power supply.
> >> >>>>>>>>> Users can potentially install modules and program and load the
> >> >>>>>>>>> supplies such as to cave in the main source, which would be really
> >> >>>>>>>>> ugly. That's against the rules in the manual, but we need to protect
> >> >>>>>>>>> things if they do it.
> >> >>>>>>>>
> >> >>>>>>>> there is quite a few high side load switches with short circuit protection
> >> >>>>>>>> and a combined current monitor / error output , but I think most of them
> >> >>>>>>>> are limited to a ~24V supply
> >> >>>>>>> The c code can shut down supply modules as needed. Each power supply
> >> >>>>>>> module has its own FPGA that the main controller can address. There's
> >> >>>>>>> no need to actually remove 48v power from the baby boards. The master
> >> >>>>>>> controller just needs to know the currents and have some reasonable
> >> >>>>>>> rules.
> >> >>>>>>
> >> >>>>>> check.
> >> >>>>>>
> >> >>>>>> depending on how good the ADC is, maybe just a resistivity divider on the 48V and after each shunt is good enough?
> >> >>>>>>
> >> >>>>>>
> >> >>>>>>
> >> >>>>>>
> >> >>>>>
> >> >>>>> Looks like we can use the XADC in the Zynq, the main controller FPGA.
> >> >>>>> That's a 1-volt full-scale, pretty terrible ADC. The voltage drop
> >> >>>>> across a shunt might be 50 mV with a common-mode of 48 volts. So we
> >> >>>>> need some sort of high-side amp.
> >> >>>>>
> >> >>>> Maybe use the idea with the resistive divider, but then don't use the
> >> >>>> ADC, use a slope converter for increased precision.
> >> >>>> That can be done with one cheap comparator, and a loop from the FPGA/Micro
> >> >>>>
> >> >>>> Add a resistor with known drop, to calibrate
> >> >>>
> >> >>> It's fun to design circuits, until some clown sells an IC that does it
> >> >>> all for you cheap. Looks like we'll use INA280, which is available and
> >> >>> costs 80 cents, according to TI.
> >> >>>
> >> >>> Digikey wants $3. Digikey has become a scalper.
> >> >>
> >> >> Or at-least an agent for a scalper. They're listing Rochester Electronics
> >> >> as supplier on some lines (other parts).
> >> >>
> >> >> sfaik digikey mostly sells to designers, people making large numbers
> >> >> of devices find their parts elsewhere.
> >> >>
> >> >Yes, nobody buys in scale from Digikey
> >> >
> >> >80cents is expensive in my world, but then again I also come from a
> >> >business where qty products sold was counted in millions
> >> We sell modest volumes of fairly expensive stuff. Parts cost is
> >> roughly 12% of sales price, and people (purchasing, engineering,
> >> manufacturing, testing) are a much bigger cost. Lately, availability
> >> dominates cost.
> >>
> >> PCBs and metal cases, both custom, are big costs.
> >>
> >> We buy a fair amount from Mouser and Digikey, expecially things like
> >> resistors that cost a fraction of a cent each.
> >>
> >> A sales guy, from Arrow or Avnet or one of the biggies, said that
> >> "distributors" don't stock parts much any more, but Mouser and Digikey
> >> do. It looks to me that Digikey at least is trending that way too;
> >> it's hard to tell right now.
> >> --
> >>
> >> I yam what I yam - Popeye
> >
> >Interesting, so what is a rule of thumb, from your perspective, to go from parts cost to the manufactured product?
> We define "direct cost" as unburdened parts cost plus labor. A selling
> price of 3x DC is our lower limit. 6s is better, sometimes 10x is
> possible where the value to the customer is high and there is no
> competition.
>
> We used to sell NMR gradient amplifiers to Varian/Agilent at maybe 4x
> DC. They marked our price up 6x to their customers.
>
> I wonder what a high-end iphone costs Apple.

afaict the estimations are that the BOM for a $1000 phone is ~$500