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tech / sci.electronics.design / resistor matrix for dummy load

resistor matrix for dummy load

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From: jlar...@highlandSNIPMEtechnology.com (John Larkin)
Newsgroups: sci.electronics.design
Subject: resistor matrix for dummy load
Date: Wed, 10 May 2023 20:15:21 -0700
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by: John Larkin - Thu, 11 May 2023 03:15 UTC

I'm still playing around with my 8-channel dummy load board. Rather
than simulating resistances electronically, it looks easier to just
switch wirewound resistors with solid-state relays.

Something like this:

https://www.dropbox.com/s/wj8y8k4tadbg99p/P945_Matrix_M3.jpg?raw=1

which can go from 41 to 1600 ohms.

The first two clusters, two resistors and three relays, allow one
resistor to be on, 2 in series, 2 in parallel, open, and short. This
sort of optimizes spreading the heat out among the resistors.

The problem is that it's really hard to think about. It can make 128
useful resistor combinations, and a lot of silly ones. Of the 128, the
sequence of resistances looks kinda goofy; we'll select a sub-list
that the customer can select from. Somehow.

Some resistance values appear several times in the list, and some have
better power dissipation sharing than others. 200 ohms is an obvious
case; it can be done 5 different ways. Seven, if some redundant cases
are included.

I wrote a couple of PowerBasic programs to analyze the legal cases,
but somebody will still have to do some hard thinking. Nice puzzle,
actually.

https://www.dropbox.com/s/d5wqv3xkznsfcuk/P945_M3_SORTED.csv.txt?dl=0

Re: resistor matrix for dummy load

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Subject: Re: resistor matrix for dummy load
From: tabbyp...@gmail.com (Tabby)
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by: Tabby - Thu, 11 May 2023 03:53 UTC

On Thursday, 11 May 2023 at 04:15:38 UTC+1, John Larkin wrote:
> I'm still playing around with my 8-channel dummy load board. Rather
> than simulating resistances electronically, it looks easier to just
> switch wirewound resistors with solid-state relays.
>
> Something like this:
>
> https://www.dropbox.com/s/wj8y8k4tadbg99p/P945_Matrix_M3.jpg?raw=1
>
> which can go from 41 to 1600 ohms.
>
> The first two clusters, two resistors and three relays, allow one
> resistor to be on, 2 in series, 2 in parallel, open, and short. This
> sort of optimizes spreading the heat out among the resistors.
>
> The problem is that it's really hard to think about. It can make 128
> useful resistor combinations, and a lot of silly ones. Of the 128, the
> sequence of resistances looks kinda goofy; we'll select a sub-list
> that the customer can select from. Somehow.
>
> Some resistance values appear several times in the list, and some have
> better power dissipation sharing than others. 200 ohms is an obvious
> case; it can be done 5 different ways. Seven, if some redundant cases
> are included.
>
> I wrote a couple of PowerBasic programs to analyze the legal cases,
> but somebody will still have to do some hard thinking. Nice puzzle,
> actually.
>
> https://www.dropbox.com/s/d5wqv3xkznsfcuk/P945_M3_SORTED.csv.txt?dl=0

Your diag shows 8 resistors, 9 relays. Is it not cheaper to use less relays & more powerful resistors?

Re: resistor matrix for dummy load

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NNTP-Posting-Date: Thu, 11 May 2023 04:14:57 +0000
From: jlar...@highlandSNIPMEtechnology.com (John Larkin)
Newsgroups: sci.electronics.design
Subject: Re: resistor matrix for dummy load
Date: Wed, 10 May 2023 21:14:58 -0700
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by: John Larkin - Thu, 11 May 2023 04:14 UTC

On Wed, 10 May 2023 20:53:47 -0700 (PDT), Tabby <tabbypurr@gmail.com>
wrote:

>On Thursday, 11 May 2023 at 04:15:38 UTC+1, John Larkin wrote:
>> I'm still playing around with my 8-channel dummy load board. Rather
>> than simulating resistances electronically, it looks easier to just
>> switch wirewound resistors with solid-state relays.
>>
>> Something like this:
>>
>> https://www.dropbox.com/s/wj8y8k4tadbg99p/P945_Matrix_M3.jpg?raw=1
>>
>> which can go from 41 to 1600 ohms.
>>
>> The first two clusters, two resistors and three relays, allow one
>> resistor to be on, 2 in series, 2 in parallel, open, and short. This
>> sort of optimizes spreading the heat out among the resistors.
>>
>> The problem is that it's really hard to think about. It can make 128
>> useful resistor combinations, and a lot of silly ones. Of the 128, the
>> sequence of resistances looks kinda goofy; we'll select a sub-list
>> that the customer can select from. Somehow.
>>
>> Some resistance values appear several times in the list, and some have
>> better power dissipation sharing than others. 200 ohms is an obvious
>> case; it can be done 5 different ways. Seven, if some redundant cases
>> are included.
>>
>> I wrote a couple of PowerBasic programs to analyze the legal cases,
>> but somebody will still have to do some hard thinking. Nice puzzle,
>> actually.
>>
>> https://www.dropbox.com/s/d5wqv3xkznsfcuk/P945_M3_SORTED.csv.txt?dl=0
>
>Your diag shows 8 resistors, 9 relays. Is it not cheaper to use less relays & more powerful resistors?

The surface-mount solid-state relays are tiny. The 5 watt wirewound
resistors are big and optimizing their use is a serious goal.

The resistors are about 1" high and I don't have room for anything
bigger.

https://www.digikey.com/en/products/detail/te-connectivity-passive-product/SQMW51R0J/2365645

I can't crowd them too much because I need air flow around them.
Paralleling helps a lot to spread the heat too.

About like this:

https://www.dropbox.com/s/j2xj60pxgifvk9w/P945_pcb_may_7.jpg?raw=1

John - possibly for your reference: some time ago I was
testing some 2 watt metal oxide resisters to get an idaea
of how hardy they are with over spec currents. Temperature
wise this went to 800 degf measured by a thermocouple.
At that point a red glow was visible at the center of the
device. Hardy they are. That device, when cool, was slightly
altered in resistance in the neighbor hood of 1 or 2 %.
They went back in the stock bin.

Hul

John Larkin <jlarkin@highlandsnipmetechnology.com> wrote:

> I'm still playing around with my 8-channel dummy load board. Rather
> than simulating resistances electronically, it looks easier to just
> switch wirewound resistors with solid-state relays.

> Something like this:

> https://www.dropbox.com/s/wj8y8k4tadbg99p/P945_Matrix_M3.jpg?raw=1

> which can go from 41 to 1600 ohms.

> The first two clusters, two resistors and three relays, allow one
> resistor to be on, 2 in series, 2 in parallel, open, and short. This
> sort of optimizes spreading the heat out among the resistors.

> The problem is that it's really hard to think about. It can make 128
> useful resistor combinations, and a lot of silly ones. Of the 128, the
> sequence of resistances looks kinda goofy; we'll select a sub-list
> that the customer can select from. Somehow.

> Some resistance values appear several times in the list, and some have
> better power dissipation sharing than others. 200 ohms is an obvious
> case; it can be done 5 different ways. Seven, if some redundant cases
> are included.

> I wrote a couple of PowerBasic programs to analyze the legal cases,
> but somebody will still have to do some hard thinking. Nice puzzle,
> actually.

> https://www.dropbox.com/s/d5wqv3xkznsfcuk/P945_M3_SORTED.csv.txt?dl=0

Re: resistor matrix for dummy load

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by: John Larkin - Fri, 12 May 2023 00:39 UTC

On Thu, 11 May 2023 23:19:00 -0000 (UTC), Hul Tytus <ht@panix.com>
wrote:

>John - possibly for your reference: some time ago I was
>testing some 2 watt metal oxide resisters to get an idaea
>of how hardy they are with over spec currents. Temperature
>wise this went to 800 degf measured by a thermocouple.
>At that point a red glow was visible at the center of the
>device. Hardy they are. That device, when cool, was slightly
>altered in resistance in the neighbor hood of 1 or 2 %.
>They went back in the stock bin.
>
>Hul

I'm going to use some 5 watt wirewounds, maybe push them to 7 watts
with air flow. I expect them to get very hot at 7 watts, and will
measure that.

Re: resistor matrix for dummy load

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by: DJ Delorie - Fri, 12 May 2023 02:35 UTC

My 3D printer came with wire wound resistors as the primary nozzle
heaters - a pair of 3W 6.8R. With 12V across them, pumping out 21W
each.

That is, until http://www.delorie.com/photos/3d_prints/img_3201.html

Re: resistor matrix for dummy load

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From: jlar...@highlandSNIPMEtechnology.com (John Larkin)
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Subject: Re: resistor matrix for dummy load
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by: John Larkin - Fri, 12 May 2023 03:05 UTC

On Thu, 11 May 2023 22:35:51 -0400, DJ Delorie <dj@delorie.com> wrote:

>
>My 3D printer came with wire wound resistors as the primary nozzle
>heaters - a pair of 3W 6.8R. With 12V across them, pumping out 21W
>each.

Makes me feel better about 7 watts into a 5 watt resistor!

>
>That is, until http://www.delorie.com/photos/3d_prints/img_3201.html

I remember an early Xerox copier that had flame detectors and CO2 fire
extinguishers inside.

My biggest hazard is probably not my ceramic resistors getting too
hot, but crisping the fiberglass PC board.

Re: resistor matrix for dummy load

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by: Martin Brown - Fri, 12 May 2023 08:30 UTC

On 11/05/2023 04:15, John Larkin wrote:
>
>
> I'm still playing around with my 8-channel dummy load board. Rather
> than simulating resistances electronically, it looks easier to just
> switch wirewound resistors with solid-state relays.
>
> Something like this:
>
> https://www.dropbox.com/s/wj8y8k4tadbg99p/P945_Matrix_M3.jpg?raw=1
>
> which can go from 41 to 1600 ohms.
>
> The first two clusters, two resistors and three relays, allow one
> resistor to be on, 2 in series, 2 in parallel, open, and short. This
> sort of optimizes spreading the heat out among the resistors.

Isn't a dead short likely to somewhat inconvenience the DUT?

I think you need to mask out K7 when K6 & K8 are closed.
Or use a slightly different network that cannot do a dead short.

__ R __[K']______
V ---[K]---| |
|_______[K']__R___

Only permits open circuit, either resistor or both.

--
Martin Brown

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From: jlar...@highlandSNIPMEtechnology.com (John Larkin)
Newsgroups: sci.electronics.design
Subject: Re: resistor matrix for dummy load
Date: Fri, 12 May 2023 07:47:24 -0700
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by: John Larkin - Fri, 12 May 2023 14:47 UTC

On Fri, 12 May 2023 09:30:13 +0100, Martin Brown
<'''newspam'''@nonad.co.uk> wrote:

>On 11/05/2023 04:15, John Larkin wrote:
>>
>>
>> I'm still playing around with my 8-channel dummy load board. Rather
>> than simulating resistances electronically, it looks easier to just
>> switch wirewound resistors with solid-state relays.
>>
>> Something like this:
>>
>> https://www.dropbox.com/s/wj8y8k4tadbg99p/P945_Matrix_M3.jpg?raw=1
>>
>> which can go from 41 to 1600 ohms.
>>
>> The first two clusters, two resistors and three relays, allow one
>> resistor to be on, 2 in series, 2 in parallel, open, and short. This
>> sort of optimizes spreading the heat out among the resistors.
>
>Isn't a dead short likely to somewhat inconvenience the DUT?

That's the point, to test the customer's gadget. I just need to be
sure that my SSRs won't blow up.

>
>I think you need to mask out K7 when K6 & K8 are closed.
>Or use a slightly different network that cannot do a dead short.
>
> __ R __[K']______
>V ---[K]---| |
> |_______[K']__R___
>
>Only permits open circuit, either resistor or both.

Short is a sellable feature. As in simulating ground faults and
inductance, which are not shown on that diagram.

Of the 512 possible relay patterns, only half make any sense and we'll
probably present, maybe, 32 to the customer.

Re: resistor matrix for dummy load

<u3mbo6$1qi73$1@news.eternal-september.org>

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by: ehsjr - Fri, 12 May 2023 21:40 UTC

On 5/10/2023 11:15 PM, John Larkin wrote:
>
>
> I'm still playing around with my 8-channel dummy load board. Rather
> than simulating resistances electronically, it looks easier to just
> switch wirewound resistors with solid-state relays.
>
> Something like this:
>
> https://www.dropbox.com/s/wj8y8k4tadbg99p/P945_Matrix_M3.jpg?raw=1

Grunble. I get error (404). Dunno if the problem is
at my end.
Ed

<snip>

Re: resistor matrix for dummy load

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by: Ari Fin - Fri, 12 May 2023 23:45 UTC

sebenarnya ini sangat baik lah, pasti

https://arcorpweb.com/tag/jasa-seo-organik/

Re: resistor matrix for dummy load

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by: Ari Fin - Fri, 12 May 2023 23:46 UTC

ada sesuatu yang bagus juga pastinya

Click here to read the complete article

Re: resistor matrix for dummy load

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by: John Larkin - Sat, 13 May 2023 02:46 UTC

On Fri, 12 May 2023 17:40:21 -0400, ehsjr <ehsjr@verizon.net> wrote:

>On 5/10/2023 11:15 PM, John Larkin wrote:
>>
>>
>> I'm still playing around with my 8-channel dummy load board. Rather
>> than simulating resistances electronically, it looks easier to just
>> switch wirewound resistors with solid-state relays.
>>
>> Something like this:
>>
>> https://www.dropbox.com/s/wj8y8k4tadbg99p/P945_Matrix_M3.jpg?raw=1
>
>Grunble. I get error (404). Dunno if the problem is
>at my end.
>Ed
>
><snip>

My bad, moving things around on Dropbox. Try this:

https://www.dropbox.com/s/r7allc4vx1u9wxx/P945_Matrix_M3.jpg?raw=1

https://www.dropbox.com/s/d5wqv3xkznsfcuk/P945_M3_SORTED.csv.txt?dl=0

Re: resistor matrix for dummy load

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Subject: Re: resistor matrix for dummy load
From: |||newsp...@nezumi.demon.co.uk (Martin Brown)
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by: Martin Brown - Sat, 13 May 2023 16:27 UTC

On Friday, May 12, 2023 at 3:49:12 PM UTC+1, John Larkin wrote:
> On Fri, 12 May 2023 09:30:13 +0100, Martin Brown
> <'''newspam'''@nonad.co.uk> wrote:
>
> >On 11/05/2023 04:15, John Larkin wrote:
> >>
> >> I'm still playing around with my 8-channel dummy load board. Rather
> >> than simulating resistances electronically, it looks easier to just
> >> switch wirewound resistors with solid-state relays.
> >>
> >> Something like this:
> >>
> >> https://www.dropbox.com/s/wj8y8k4tadbg99p/P945_Matrix_M3.jpg?raw=1
> >>
> >> which can go from 41 to 1600 ohms.
> >>
> >> The first two clusters, two resistors and three relays, allow one
> >> resistor to be on, 2 in series, 2 in parallel, open, and short. This
> >> sort of optimizes spreading the heat out among the resistors.

But it shows a distinct lack of imagination to have them as identical resistors in each leg.
You get an extra value for nothing if you use Golden ratio resistors. eg

E48 100 and 162

Single plus parallel and series combos of those give you 62, 100, 162, 262
1/phi 1 phi phi^2

or E24 100, 100+62

You can eliminate some relays or offer a finer range of values with the same amount of hardware.

> >Isn't a dead short likely to somewhat inconvenience the DUT?
> That's the point, to test the customer's gadget. I just need to be
> sure that my SSRs won't blow up.
> >
> >I think you need to mask out K7 when K6 & K8 are closed.
> >Or use a slightly different network that cannot do a dead short.
> >
> > __ R __[K']______
> >V ---[K]---| |
> > |_______[K']__R___
> >
> >Only permits open circuit, either resistor or both.

> Short is a sellable feature. As in simulating ground faults and
> inductance, which are not shown on that diagram.

You might want to make the relay for doing a dead short a bit more beefy than the others and protected by a slow blow fuse.
I recall one design where an SSR once caught fire because of over current.

> Of the 512 possible relay patterns, only half make any sense and we'll
> probably present, maybe, 32 to the customer.

Worthwhile making as many as possible make sense if you can.
Regards,
Martin Brown

Re: resistor matrix for dummy load

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by: ehsjr - Sat, 13 May 2023 18:05 UTC

On 5/12/2023 10:46 PM, John Larkin wrote:
> On Fri, 12 May 2023 17:40:21 -0400, ehsjr <ehsjr@verizon.net> wrote:
>
>> On 5/10/2023 11:15 PM, John Larkin wrote:
>>>
>>>
>>> I'm still playing around with my 8-channel dummy load board. Rather
>>> than simulating resistances electronically, it looks easier to just
>>> switch wirewound resistors with solid-state relays.
>>>
>>> Something like this:
>>>
>>> https://www.dropbox.com/s/wj8y8k4tadbg99p/P945_Matrix_M3.jpg?raw=1
>>
>> Grunble. I get error (404). Dunno if the problem is
>> at my end.
>> Ed
>>
>> <snip>
>
> My bad, moving things around on Dropbox. Try this:
>
> https://www.dropbox.com/s/r7allc4vx1u9wxx/P945_Matrix_M3.jpg?raw=1
>
> https://www.dropbox.com/s/d5wqv3xkznsfcuk/P945_M3_SORTED.csv.txt?dl=0
>
>
>

Thanks!
Ed

Re: resistor matrix for dummy load

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Subject: Re: resistor matrix for dummy load
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by: John Larkin - Sat, 13 May 2023 19:06 UTC

On Sat, 13 May 2023 09:27:39 -0700 (PDT), Martin Brown
<|||newspam|||@nezumi.demon.co.uk> wrote:

>On Friday, May 12, 2023 at 3:49:12?PM UTC+1, John Larkin wrote:
>> On Fri, 12 May 2023 09:30:13 +0100, Martin Brown
>> <'''newspam'''@nonad.co.uk> wrote:
>>
>> >On 11/05/2023 04:15, John Larkin wrote:
>> >>
>> >> I'm still playing around with my 8-channel dummy load board. Rather
>> >> than simulating resistances electronically, it looks easier to just
>> >> switch wirewound resistors with solid-state relays.
>> >>
>> >> Something like this:
>> >>
>> >> https://www.dropbox.com/s/wj8y8k4tadbg99p/P945_Matrix_M3.jpg?raw=1
>> >>
>> >> which can go from 41 to 1600 ohms.
>> >>
>> >> The first two clusters, two resistors and three relays, allow one
>> >> resistor to be on, 2 in series, 2 in parallel, open, and short. This
>> >> sort of optimizes spreading the heat out among the resistors.
>
>But it shows a distinct lack of imagination to have them as identical resistors in each leg.
>You get an extra value for nothing if you use Golden ratio resistors. eg
>
>E48 100 and 162

A conductance DAC (R, 2R, 4R...) is even better. 2 is an even golder
number than phi.

But I want to maximize allowable power dissipation with 5 watt
resistors. And we can get quantity discounts on lots of 100 ohm
resistors. And 162 is not a stocked wirewound value.

Of course I considered different values for the second group. And of
course your defaut mode is to insult. You wouldn't dare do that in a
pub.

>
>Single plus parallel and series combos of those give you 62, 100, 162, 262
>1/phi 1 phi phi^2
>
>or E24 100, 100+62
>
>You can eliminate some relays or offer a finer range of values with the same amount of hardware.
>
>> >Isn't a dead short likely to somewhat inconvenience the DUT?
>> That's the point, to test the customer's gadget. I just need to be
>> sure that my SSRs won't blow up.
>> >
>> >I think you need to mask out K7 when K6 & K8 are closed.
>> >Or use a slightly different network that cannot do a dead short.
>> >
>> > __ R __[K']______
>> >V ---[K]---| |
>> > |_______[K']__R___
>> >
>> >Only permits open circuit, either resistor or both.
>
>> Short is a sellable feature. As in simulating ground faults and
>> inductance, which are not shown on that diagram.
>
>You might want to make the relay for doing a dead short a bit more beefy than the others and protected by a slow blow fuse.
>I recall one design where an SSR once caught fire because of over current.

We will turn on all 9 relays to make the short. It shows a distinct
lack of imagination that you didn't see that.

Would an SSR be protected by a slow-blow fuse? I suspect not.

>
>> Of the 512 possible relay patterns, only half make any sense and we'll
>> probably present, maybe, 32 to the customer.
>
>Worthwhile making as many as possible make sense if you can.

The big resistors are 5% so having too many steps will be
non-monotonic and look silly. And it's just a dummy load that pretends
to be solenoids and torque motors which aren't precise anyhow.

>Regards,
>Martin Brown

Re: resistor matrix for dummy load

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by: Ari Fin - Mon, 12 Jun 2023 00:54 UTC

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Re: resistor matrix for dummy load

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by: neo5...@gmail.com - Mon, 12 Jun 2023 18:40 UTC

On Thursday, May 11, 2023 at 7:19:09 PM UTC-4, Hul Tytus wrote:
> John - possibly for your reference: some time ago I was
> testing some 2 watt metal oxide resisters to get an idaea
> of how hardy they are with over spec currents. Temperature
> wise this went to 800 degf measured by a thermocouple.
> At that point a red glow was visible at the center of the
> device. Hardy they are. That device, when cool, was slightly
> altered in resistance in the neighbor hood of 1 or 2 %.
> They went back in the stock bin.
>
> Hul
> John Larkin <jla...@highlandsnipmetechnology.com> wrote:
>
>
> > I'm still playing around with my 8-channel dummy load board. Rather
> > than simulating resistances electronically, it looks easier to just
> > switch wirewound resistors with solid-state relays.
>
> > Something like this:
>
> > https://www.dropbox.com/s/wj8y8k4tadbg99p/P945_Matrix_M3.jpg?raw=1
>
> > which can go from 41 to 1600 ohms.
>
> > The first two clusters, two resistors and three relays, allow one
> > resistor to be on, 2 in series, 2 in parallel, open, and short. This
> > sort of optimizes spreading the heat out among the resistors.
>
> > The problem is that it's really hard to think about. It can make 128
> > useful resistor combinations, and a lot of silly ones. Of the 128, the
> > sequence of resistances looks kinda goofy; we'll select a sub-list
> > that the customer can select from. Somehow.
>
> > Some resistance values appear several times in the list, and some have
> > better power dissipation sharing than others. 200 ohms is an obvious
> > case; it can be done 5 different ways. Seven, if some redundant cases
> > are included.
>
> > I wrote a couple of PowerBasic programs to analyze the legal cases,
> > but somebody will still have to do some hard thinking. Nice puzzle,
> > actually.
>
> > https://www.dropbox.com/s/d5wqv3xkznsfcuk/P945_M3_SORTED.csv.txt?dl=0

Another choice are the White Cement types. They are designed to run smoking hot.

-dbc

Re: resistor matrix for dummy load

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From: jlar...@highlandSNIPMEtechnology.com (John Larkin)
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Subject: Re: resistor matrix for dummy load
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by: John Larkin - Mon, 12 Jun 2023 19:24 UTC

On Mon, 12 Jun 2023 11:40:26 -0700 (PDT), "neo5...@gmail.com"
<neo5bass@gmail.com> wrote:

>On Thursday, May 11, 2023 at 7:19:09?PM UTC-4, Hul Tytus wrote:
>> John - possibly for your reference: some time ago I was
>> testing some 2 watt metal oxide resisters to get an idaea
>> of how hardy they are with over spec currents. Temperature
>> wise this went to 800 degf measured by a thermocouple.
>> At that point a red glow was visible at the center of the
>> device. Hardy they are. That device, when cool, was slightly
>> altered in resistance in the neighbor hood of 1 or 2 %.
>> They went back in the stock bin.
>>
>> Hul
>> John Larkin <jla...@highlandsnipmetechnology.com> wrote:
>>
>>
>> > I'm still playing around with my 8-channel dummy load board. Rather
>> > than simulating resistances electronically, it looks easier to just
>> > switch wirewound resistors with solid-state relays.
>>
>> > Something like this:
>>
>> > https://www.dropbox.com/s/wj8y8k4tadbg99p/P945_Matrix_M3.jpg?raw=1
>>
>> > which can go from 41 to 1600 ohms.
>>
>> > The first two clusters, two resistors and three relays, allow one
>> > resistor to be on, 2 in series, 2 in parallel, open, and short. This
>> > sort of optimizes spreading the heat out among the resistors.
>>
>> > The problem is that it's really hard to think about. It can make 128
>> > useful resistor combinations, and a lot of silly ones. Of the 128, the
>> > sequence of resistances looks kinda goofy; we'll select a sub-list
>> > that the customer can select from. Somehow.
>>
>> > Some resistance values appear several times in the list, and some have
>> > better power dissipation sharing than others. 200 ohms is an obvious
>> > case; it can be done 5 different ways. Seven, if some redundant cases
>> > are included.
>>
>> > I wrote a couple of PowerBasic programs to analyze the legal cases,
>> > but somebody will still have to do some hard thinking. Nice puzzle,
>> > actually.
>>
>> > https://www.dropbox.com/s/d5wqv3xkznsfcuk/P945_M3_SORTED.csv.txt?dl=0
>
>
>Another choice are the White Cement types. They are designed to run smoking hot.
>
>-dbc

I considered axial resistors. The ceramic ones can run very hot. But
we'd have to stand them off the board somehow to avoid scorching the
PCB material. Possibly some sort of fancy lead forming. Tricky to
assemble.

The stand-up 5-watt square resistors are easy to insert and to
automated solder. The question is, how hot will the PCB get vs power
per resistor, at some given air flow?

https://www.digikey.com/en/products/detail/te-connectivity-passive-product/SQMW51R0J/2365645

I don't really mind the resistor surface getting very hot.

Re: resistor matrix for dummy load

<u68tm3$178jr$1@solani.org>

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From: ali...@comet.invalid (Jan Panteltje)
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Subject: Re: resistor matrix for dummy load
Date: Tue, 13 Jun 2023 05:09:22 GMT
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by: Jan Panteltje - Tue, 13 Jun 2023 05:09 UTC

On a sunny day (Mon, 12 Jun 2023 12:24:10 -0700) it happened John Larkin
<jlarkin@highlandSNIPMEtechnology.com> wrote in
<4pre8ilnovvis410t9g535pvsmpvehq14s@4ax.com>:

>The stand-up 5-watt square resistors are easy to insert and to
>automated solder. The question is, how hot will the PCB get vs power
>per resistor, at some given air flow?
>
>https://www.digikey.com/en/products/detail/te-connectivity-passive-product/SQMW51R0J/2365645
>
>I don't really mind the resistor surface getting very hot.

One worry would perhaps be these resistors un-soldering themselves, causing bad solder joint.
I have seen transformer pins unsoldering in TV sets.

Personally I would move power resistors to a heat sink.
Have peeseebees become a religion?

Re: resistor matrix for dummy load

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Subject: Re: resistor matrix for dummy load
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by: John Larkin - Tue, 13 Jun 2023 14:32 UTC

On Tue, 13 Jun 2023 05:09:22 GMT, Jan Panteltje <alien@comet.invalid>
wrote:

>On a sunny day (Mon, 12 Jun 2023 12:24:10 -0700) it happened John Larkin
><jlarkin@highlandSNIPMEtechnology.com> wrote in
><4pre8ilnovvis410t9g535pvsmpvehq14s@4ax.com>:
>
>>The stand-up 5-watt square resistors are easy to insert and to
>>automated solder. The question is, how hot will the PCB get vs power
>>per resistor, at some given air flow?
>>
>>https://www.digikey.com/en/products/detail/te-connectivity-passive-product/SQMW51R0J/2365645
>>
>>I don't really mind the resistor surface getting very hot.
>
>One worry would perhaps be these resistors un-soldering themselves, causing bad solder joint.
>I have seen transformer pins unsoldering in TV sets.

And soldering-type temps will damage the board and other components.
The power resistor pads will have to be giant on layers 1 and 6, to
transfer heat into the copper planes on 2 and 5.

>
>Personally I would move power resistors to a heat sink.
>Have peeseebees become a religion?

Heat sinks are big and expensive, and I'd have to mount my many
resistors to the heat sinks. That's messy and labor intensive.

Peeseebees are cheap and can be machine assembled in panels.

Subject	Author
resistor matrix for dummy load	John Larkin
Re: resistor matrix for dummy load	Tabby
Re: resistor matrix for dummy load	John Larkin
Re: resistor matrix for dummy load	Hul Tytus
Re: resistor matrix for dummy load	John Larkin
Re: resistor matrix for dummy load	DJ Delorie
Re: resistor matrix for dummy load	John Larkin
Re: resistor matrix for dummy load	neo5...@gmail.com
Re: resistor matrix for dummy load	John Larkin
Re: resistor matrix for dummy load	Jan Panteltje
Re: resistor matrix for dummy load	John Larkin
Re: resistor matrix for dummy load	Martin Brown
Re: resistor matrix for dummy load	John Larkin
Re: resistor matrix for dummy load	Martin Brown
Re: resistor matrix for dummy load	John Larkin
Re: resistor matrix for dummy load	Ari Fin
Re: resistor matrix for dummy load	ehsjr
Re: resistor matrix for dummy load	John Larkin
Re: resistor matrix for dummy load	ehsjr
Re: resistor matrix for dummy load	Ari Fin
Re: resistor matrix for dummy load	Ari Fin