On 15/03/2024 10:51, Ahem A Rivet's Shot wrote:
> Watts
> per hour is meaningless.

Not as a ramp rate for a power station :-)

--
“The urge to save humanity is almost always only a false face for the
urge to rule it.”
– H. L. Mencken

On Fri, 15 Mar 2024 16:13:46 +0000
The Natural Philosopher <tnp@invalid.invalid> wrote:

> On 15/03/2024 10:51, Ahem A Rivet's Shot wrote:
> > Watts
> > per hour is meaningless.
>
> Not as a ramp rate for a power station :-)

<grin> Fair enough.

--
Steve O'Hara-Smith
Odds and Ends at http://www.sohara.org/
For forms of government let fools contest
Whate're is best administered is best - Alexander Pope

On 14/03/2024 18:11, bp@www.zefox.net wrote:
> Mike Scott <usenet.16@scottsonline.org.uk.invalid> wrote:
>> On 14/03/2024 15:51, Joe wrote:
>>> I'm using a cheap APC, I believe 650 or 750, with USB monitoring hookup. Also have my router connected (with VOIP) to keep
>>> communication possible for a little while (runtime abt 30 minutes). Battery replaced once, I believe it was some 7 years old.
>>
>> Somehow that makes no sense to me..... current 650 is 227 pounds (maybe plus
>> VAT) on the APC website. 5 times the cost of the Pi. I'm sure it's a
>> very nice UPS, but.... ???
>>
>
> Sense or not, it seems to be a fact of life. The inverter/charger/transfer units
> I used have vanished from Amazon, replace by units with four times the power and
> double the price. Battery prices seem to have dropped very slightly, but are
> still a whisker over $200/kWH.
>
> A 12 volt to 5 volt stepdown converter appears to be less than $10, small 12 volt
> batteries range from $20-100 in the few AH range, a 12 volt 5 amp charger ranges
> from $11 to $50. The charger would be the iffy part, since a smart charger on a
> loaded battery is apt to get confused by what looks like high self-discharge..
>
> Something reliable for less than $100 will take both luck and ingenuity. One
> possibility is finding a used UPS unit in e-waste and replacing the battery.
>
> bob prohaska

Seems the rechargeable bit is the issue. For my part, and purely to use
as a short-term standby for the Pi until mains resumes or the system can
shut down cleanly - I'd be happy with something with a bundle of AA
cells or similar. I doubt a clean switchover circuit would be difficult
to design, but my electronics knowledge is decades out of date :-{

--
Mike Scott
Harlow, England

Mike Scott <usenet.16@scottsonline.org.uk.invalid> wrote:
>
> Seems the rechargeable bit is the issue. For my part, and purely to use
> as a short-term standby for the Pi until mains resumes or the system can
> shut down cleanly - I'd be happy with something with a bundle of AA
> cells or similar. I doubt a clean switchover circuit would be difficult
> to design, but my electronics knowledge is decades out of date :-{

Since I started mucking about with inverters the complexity of line
detection has gradually dawned on me. I started out thinking of a
simple SPDT relay with coil across the line. Line drops, relay
goes to normal contacts, job done. With enough filter caps on
the Pi to sustain it through a few line cycles maybe that would
work. For a larger load the caps get big, if you want (as I do)
to back up several different devices (DSL modem, router, switches)
that amounts to a custom DC supply interconnecting all devices.

If you want significant endurance (minutes or hours) capacitors
become impractical. Primary cells in series with a blocking
diode (6 volt battery with one silicon diode in series) would
get you close to 5 volts with the diode drop. Maybe that's
your ticket. The key is finding the right battery chemistry
to give the voltage you need. Still, it's a handmade gadget.
And, whatever voltage matching device you select must not
drain the primary cells. I think a three-terminal regulator
would cause at least some trouble on that count. On the good
side, you could put it all downstream of the Pi power supply
and skip line detection entirely. That's a big advantage.
When line voltage drops (and returns) it's often noisy, dropping,
returning and dropping again. Much better if the UPS takes over
with a hair trigger and waits for a period of quiet before retiring.
That's where the logic gets intricate.

I puzzled over the custom DC supply versus off-the-shelf AC UPS
approach and settled on the latter. For a single Pi, that no
longer looks so attractive.

Thanks for reading,

bob prohaska

bp@www.zefox.net wrote:
> side, you could put it all downstream of the Pi power supply
> and skip line detection entirely. That's a big advantage.
>
On second thought, this is probably wrong. If one connects
to a Pi a 5 volt supply in parallel with a blocking diode
and a 6 volt battery, the diode is still forward biased
and will drain the battery eventually. Some kind of switch
is needed, controlled by line detection.

Maybe a three terminal regulator set for 5 volts out powered
by a 9 (or higher) volt battery pack could be substituted.
Still, one has to consider the idle draw of the regulator.
TI's LM340 takes 6 mA roughly. Still, that's a smallish
supply for a Pi. You'll likely want something larger.

Apologies for the red herring!

bob prohaska

In message <ut4mge$30t2r$1@dont-email.me>
<bp@www.zefox.net> wrote:

> bp@www.zefox.net wrote:
> > side, you could put it all downstream of the Pi power supply and skip
> > line detection entirely. That's a big advantage.
> >
> On second thought, this is probably wrong. If one connects to a Pi a 5 volt
> supply in parallel with a blocking diode and a 6 volt battery, the diode is
> still forward biased and will drain the battery eventually. Some kind of
> switch is needed, controlled by line detection.
>
> Maybe a three terminal regulator set for 5 volts out powered by a 9 (or
> higher) volt battery pack could be substituted. Still, one has to consider
> the idle draw of the regulator. TI's LM340 takes 6 mA roughly. Still,
> that's a smallish supply for a Pi. You'll likely want something larger.

It is possible to switch between mains and backup using MOSFETs, so you
can get the voltage drop of the switching device arbitrarily low, and a
switchover time of a microsecond or so - it doesn't need to be quite
that quick, but it probably wants to be quicker than a mechanical relay.
/If/ you want the negative line to be common, and the switch to be in
the positive line, you need to use P-channel MOSFETS. And remember the
presence and direction of the body diode, so you'll want to connect
source and drain the opposite way round from what you might imagine.

You'll need a reliable detector of the presence of mains, and probably
also that the output is high enough before you swap back to mains.

Most people are accustomed to working with N-channel devices and not
thinking about the body diode, so you might find the mental gymnastics
very hard, but it can be done!

The prize is that normal running will definitely be from mains, even
if the output voltage of the mains supply is slightly lower than that
of the backup regulator.

David

On 16/03/2024 17:56, bp@www.zefox.net wrote:
> bp@www.zefox.net wrote:
>> side, you could put it all downstream of the Pi power supply
>> and skip line detection entirely. That's a big advantage.
>>
> On second thought, this is probably wrong. If one connects
> to a Pi a 5 volt supply in parallel with a blocking diode
> and a 6 volt battery, the diode is still forward biased
> and will drain the battery eventually. Some kind of switch
> is needed, controlled by line detection.
>
> Maybe a three terminal regulator set for 5 volts out powered
> by a 9 (or higher) volt battery pack could be substituted.
> Still, one has to consider the idle draw of the regulator.
> TI's LM340 takes 6 mA roughly. Still, that's a smallish
> supply for a Pi. You'll likely want something larger.
>
> Apologies for the red herring!
>
> bob prohaska
>
I think the chances of finding an 'ideal' battery are relatively slender.
You are likely forced into some sort of 5v switched mode regulator - and
its probably wisests at least for a single Pi - to have that permanently
delivering power and just have the battery on permanent mild charge
--
The New Left are the people they warned you about.

Re: Re: Backup power supply
By: Andriy D to Richard Falken on Thu Mar 14 2024 07:57 am

> You mean full blown AC UPS, like APC used to do? Or do you know some well-kn
> brands producing USB UPS?
>

Yes, I was thinking a full UPS with an USB port for control. APC has some
models that would do. Cyberpower also does have some very nice ones for
domestic purposes.

--
gopher://gopher.richardfalken.com/1/richardfalken

Re: Re: Backup power supply
By: Mike Scott to Joe on Thu Mar 14 2024 04:32 pm

> Somehow that makes no sense to me..... current 650 is £227 (maybe plus
> VAT) on the APC website. 5 times the cost of the Pi. I'm sure it's a
> very nice UPS, but.... ???
>

Well, any battery (without controllers or anything, just the battery) is going
to be expensive as heck. I think the trick is using the same battery for a
bunch of mini-appliances so you don't feel stupid spending many hundred bucks
for backing a single machine worth 30 bucks...

--
gopher://gopher.richardfalken.com/1/richardfalken

On Sat, 16 Mar 2024 15:27:05 +0000, Mike Scott
<usenet.16@scottsonline.org.uk.invalid> wrote:

> ... For my part, and purely to use
> as a short-term standby for the Pi until mains resumes or the system can
> shut down cleanly

Please note that the Pi still draws power after shutdown,
because it has no power-off circuit of any kind.
There is a small but significant stand-by current (not just any
LEDs) that will eventually drain the UPS/batteries/whatever.
A dumb power source should at least be over-discharge protected
(think of protected Lithium batteries) or not be damaged by
total discharge.

Another issue: If grid power is restored before the UPS is
empty, the pi will not boot automatically. It only knows how to
handle unplug - replug the USB power.

So a good solution should remove power from the Pi after
shutdown, and switch it on again once the grid power is back.

Like David Higton suggests, MOSFETS are great for that.

--
Regards,
Kees Nuyt

The Natural Philosopher <tnp@invalid.invalid> wrote:
> I think the chances of finding an 'ideal' battery are relatively slender.
> You are likely forced into some sort of 5v switched mode regulator - and
> its probably wisests at least for a single Pi - to have that permanently
> delivering power and just have the battery on permanent mild charge

It's certainly the simplest solution from off-the-shelf parts.
Standard dc-dc converter, standard battery, standard charger.
No need for a handmade line power loss detector.

Efficiency won't be great. For one, or even several, Pis
that's not a problem. But it will likely be somewhere close
to $100 for a halfway decent battery and charger.

bob prohaska

On 15/03/2024 10:51, Ahem A Rivet's Shot wrote:
>> Make that 5 minutes * 500W/5W or 500 minutes which is indeed a
>> long time but a lot shorter than the 150 hours you were expecting.

On 3/15/2024 6:43 AM, druck wrote:
> If you want 150 hours, you need to be looking at a backup generator,
> so your UPS only needs to last as long as it takes for your generator
> to fire up.
>
> That's usually a couple of minutes for professional diesel ones, but
> as its home setup it might take you a few minutes to connect it up and
> pull the starter cord on a cheap petrol one.
>
> It might then take a few more minutes to drain the tank of the sludge
> that used to be fuel last time you used it, and to run to the garage
> to get some fresh petrol.
>
> It might take a few more minutes if your spark plugs have been fouled
> as you didn't clean it after use, and your air filter has a hundred
> different types of bugs living it.
>
> So make sure the UPS lasts an hour or 2.
>
> Oh and once you've managed to get it going, and it's making a
> tremendous racket, just remember everyone else in the neighbourhood
> who is without power will be turning to look in your direction...

I read this and feel first-world superiority for having last year
installed a 14kW Generac system, powered by our municipal natural gas
supply. In case of a power outage, it kicks in within about 10 seconds.
When the grid comes back up, it syncs the AC to the grid before pulling
the relay to reconnect. And every other Wednesday, it tests itself for
10 minutes, synchronizing before going off-grid as well as before going
back on-grid.
In case the muni gas is down, my electrician will come over and install
the propane conversion kit. (I don't have a good place to keep propane
tanks.)

-- Lars

On 3/13/2024 4:14 PM, bp@www.zefox.net wrote:
> For one Pi a 5 volt regulator connected to a battery
> that's held on a float charger is probably the cheapest,

That is what I used for my CPAP which has a 12V input for use when
camping. A motorcycle battery and a trickle charger.

But since then, I installed a backup generator for the whole house, so
the wife wanted the jerry-rigged UPS out of the house.

-- Lars

Re: Fwd: Backup power supply
By: Lars Poulsen to Ahem A Rivet's Shot on Fri Apr 05 2024 02:08 pm

> I read this and feel first-world superiority for having last year
> installed a 14kW Generac system, powered by our municipal natural gas
> supply. In case of a power outage, it kicks in within about 10 seconds.

My house is completly offgriddable because it has a 6 kW PV array, a 6kW diesel
generator and a battery bank worth 15 kWh (which is way more electricity than
my house uses up in a day).

Switching power sources caries 0 downtime. The controller is automatable.

I'd argue something like this is the proper way of running an uninterrupted
supply of power for home but I also think this is way out of the scope of the
discussion. Nobody in their right mind spend 20 kilobucks in a supply system
for a computer worth 80 bucks.
--
gopher://gopher.richardfalken.com/1/richardfalken

On 05/04/2024 22:08, Lars Poulsen wrote:
> On 15/03/2024 10:51, Ahem A Rivet's Shot wrote:
> >>     Make that 5 minutes * 500W/5W or 500 minutes which is indeed a
> >> long time but a lot shorter than the 150 hours you were expecting.
>
> On 3/15/2024 6:43 AM, druck wrote:
> > If you want 150 hours, you need to be looking at a backup generator,
> > so your UPS only needs to last as long as it takes for your generator
> > to fire up.
> >
> > That's usually a couple of minutes for professional diesel ones, but
> > as its home setup it might take you a few minutes to connect it up and
> > pull the starter cord on a cheap petrol one.
> >
> > It might then take a few more minutes to drain the tank of the sludge
> > that used to be fuel last time you used it, and to run to the garage
> > to get some fresh petrol.
> >
> > It might take a few more minutes if your spark plugs have been fouled
> > as you didn't clean it after use, and your air filter has a hundred
> > different types of bugs living it.
> >
> > So make sure the UPS lasts an hour or 2.
> >
> > Oh and once you've managed to get it going, and it's making a
> > tremendous racket, just remember everyone else in the neighbourhood
> > who is without power will be turning to look in your direction...
>
> I read this and feel first-world superiority for having last year
> installed a 14kW Generac system, powered by our municipal natural gas
> supply. In case of a power outage, it kicks in within about 10 seconds.
> When the grid comes back up, it syncs the AC to the grid before pulling
> the relay to reconnect. And every other Wednesday, it tests itself for
> 10 minutes, synchronizing before going off-grid as well as before going
> back on-grid.
> In case the muni gas is down, my electrician will come over and install
> the propane conversion kit. (I don't have a good place to keep propane
> tanks.)
>
> -- Lars

I think I will print a small nuclear reactor on my 3D printer and go off
grid entirely :-) :-)

--
“Some people like to travel by train because it combines the slowness of
a car with the cramped public exposure of 
an airplane.”

Dennis Miller

On 05/04/2024 06:46, Richard Falken wrote:
> Re: Fwd: Backup power supply
> By: Lars Poulsen to Ahem A Rivet's Shot on Fri Apr 05 2024 02:08 pm
>
> > I read this and feel first-world superiority for having last year
> > installed a 14kW Generac system, powered by our municipal natural gas
> > supply. In case of a power outage, it kicks in within about 10 seconds.
>
> My house is completly offgriddable because it has a 6 kW PV array, a 6kW diesel
> generator and a battery bank worth 15 kWh (which is way more electricity than
> my house uses up in a day).
>
> Switching power sources caries 0 downtime. The controller is automatable.
>
> I'd argue something like this is the proper way of running an uninterrupted
> supply of power for home but I also think this is way out of the scope of the
> discussion. Nobody in their right mind spend 20 kilobucks in a supply system
> for a computer worth 80 bucks.
> --
> gopher://gopher.richardfalken.com/1/richardfalken

It also amuses me how people think that the electricity that powers
their homes is all the energy footprint they have.

I wonder how many lumps of coal a typical Raspberry Pi burns in its
manufacture and shipment.

Or how much diesel goes into the organic vegetable basket they buy...

--
“Some people like to travel by train because it combines the slowness of
a car with the cramped public exposure of 
an airplane.”

Dennis Miller

The Natural Philosopher <tnp@invalid.invalid> writes:

> It also amuses me how people think that the electricity that powers
> their homes is all the energy footprint they have.
>
> I wonder how many lumps of coal a typical Raspberry Pi burns in its
> manufacture and shipment.
>
> Or how much diesel goes into the organic vegetable basket they buy...

And how much lemon juice they need per day to stay invisible?

CNR.

--
I do not bite, I just want to play.

On Sat, 6 Apr 2024 09:32:01 +0100
The Natural Philosopher <tnp@invalid.invalid> wrote:

> I think I will print a small nuclear reactor on my 3D printer and go off
> grid entirely :-) :-)

Hmm thorium loaded filament, some technical difficulties just a
small matter of engineering.

--
Steve O'Hara-Smith
Odds and Ends at http://www.sohara.org/
For forms of government let fools contest
Whate're is best administered is best - Alexander Pope

On 6 Apr 2024 at 08:32:01, The Natural Philosopher <tnp@invalid.invalid> wrote:
>
> I think I will print a small nuclear reactor on my 3D printer and go off
> grid entirely :-) :-)
>

So you finally bought one?
What did you get?

The Natural Philosopher <tnp@invalid.invalid> wrote:
>
> I think I will print a small nuclear reactor on my 3D printer and go off
> grid entirely :-) :-)

I printed this a few years ago in glow-in-the-dark plastic:
http://web.archive.org/web/20170209140207/http://www.thingiverse.com/thing:1561276/

The cooling towers make a handy pen holder at the scale I used. But
now it looks like the nuclear regulators have caught on and had the
3D model pulled off Thingiverse! :)

--
__ __
#_ < |\| |< _#

On 7 Apr 2024 17:28:19 +1000
Computer Nerd Kev <not@telling.you.invalid> wrote:

> The Natural Philosopher <tnp@invalid.invalid> wrote:
> >
> > I think I will print a small nuclear reactor on my 3D printer and go
> > off grid entirely :-) :-)
>
> I printed this a few years ago in glow-in-the-dark plastic:
> http://web.archive.org/web/20170209140207/http://www.thingiverse.com/thing:1561276/
>
> The cooling towers make a handy pen holder at the scale I used. But
> now it looks like the nuclear regulators have caught on and had the
> 3D model pulled off Thingiverse! :)

Yet worse the wayback machine didn't archive the STL (can't say I
blame them).

--
Steve O'Hara-Smith
Odds and Ends at http://www.sohara.org/
For forms of government let fools contest
Whate're is best administered is best - Alexander Pope

On 07/04/2024 06:51, Bob Martin wrote:
> On 6 Apr 2024 at 08:32:01, The Natural Philosopher <tnp@invalid.invalid> wrote:
>>
>> I think I will print a small nuclear reactor on my 3D printer and go off
>> grid entirely :-) :-)
>>
>
> So you finally bought one?
> What did you get?
>
I am awaiting delivery of a Creality K1

I was attracted by the open source nature of its software, however there
are an awful lot of knobs to twiddle on the slicers.

PS Creality's slicer doesn't work on linux. Crashes.

--
Microsoft : the best reason to go to Linux that ever existed.

On Sun, 7 Apr 2024 09:55:32 +0100
The Natural Philosopher <tnp@invalid.invalid> wrote:

> I was attracted by the open source nature of its software, however there
> are an awful lot of knobs to twiddle on the slicers.

You will eventually want to come to a deep and meaningful
understanding of pretty much all of them, but they should have sane
defaults to get you going, then it's a matter of learning what to tweak to
fix which defect.

My upgrade plans got put on hold - and now they're talking about
the V-Core 4 coming soon.

--
Steve O'Hara-Smith
Odds and Ends at http://www.sohara.org/
For forms of government let fools contest
Whate're is best administered is best - Alexander Pope

On 07/04/2024 10:20, Ahem A Rivet's Shot wrote:
> On Sun, 7 Apr 2024 09:55:32 +0100
> The Natural Philosopher <tnp@invalid.invalid> wrote:
>
>> I was attracted by the open source nature of its software, however there
>> are an awful lot of knobs to twiddle on the slicers.
>
> You will eventually want to come to a deep and meaningful
> understanding of pretty much all of them,

I feared as much :-(

>but they should have sane
> defaults to get you going, then it's a matter of learning what to tweak to
> fix which defect.
Indeed. I take it that the applied tweaks can be stored both in the
resultant G code file, fir that specific object, and in terms of a
generic sort of configuration like
"Creality-K1-PLA-print-with-deep-overhangs"

>
> My upgrade plans got put on hold - and now they're talking about
> the V-Core 4 coming soon.
>

well it seems to me that rather as with gearheads in music, its more
important to play the instruments you have than constantly seek to
acquire better ones.

--
Microsoft : the best reason to go to Linux that ever existed.

The Natural Philosopher <tnp@invalid.invalid> wrote:
> On 07/04/2024 10:20, Ahem A Rivet's Shot wrote:
>> My upgrade plans got put on hold - and now they're talking about
>> the V-Core 4 coming soon.
>>
>
> well it seems to me that rather as with gearheads in music, its more
> important to play the instruments you have than constantly seek to
> acquire better ones.

I sure think so, I'm still using my MakerBot Cupcake CNC:
https://en.wikipedia.org/wiki/MakerBot#Cupcake_CNC

--
__ __
#_ < |\| |< _#