[arm-allstar] Notes on under voltage problem

[Doug Crompton]

Jim,

 Are you using the download image from hamvoip.org that was in the last
month or so. That image now supports the 3B+ and is a latter kernel than
the current update distribution. So if you downloaded the image in the last
month or so the later image includes the low voltage message. We will be
putting out that update from everyone (to the new kernel) soon. I suspect
many will find they get the message with under-voltage supplies.

I am not sure what the set point is for under voltage but just because you
get the message does not necessarily mean your Pi will malfunction. The
actual processor and peripherals run on other regulators from the 5V line -
3.3 and 1.2 volts. It is however a warning that could be eliminated with a
proper supply.


*73 Doug*

*WA3DSP*

*http://www.crompton.com/hamradio <http://www.crompton.com/hamradio>*


On Thu, May 17, 2018 at 5:12 PM, "Jim Darrough via arm-allstar" <
arm-allstar at hamvoip.org> wrote:

> My setup is with a Pi 3B, not B+. WHen I was using an Adafruit 2.4 amp
> power supply, no messages. Went back to a 1 amp power supply, messages came
> back. I don't think the b+ actually causes the problem, but I can see where
> it might draw more current. Voltage sag can occur (as Doug mentions) with
> current that comes close to maximum on any device.
>
> Doug, is it possible the last updates have resulted in this happening?
> Maybe there was no monitoring until then?
>
> 73 Jim KI7AY
>
>
> On 05/17/2018 12:43 AM, "Doug Crompton via arm-allstar" wrote:
>
>> The Pi3B+ has a more advanced power and monitoring system. If you get a
>> low
>> voltage message it is probably worth looking into. The key here is under
>> voltage and while this could be due to an under current power supply it
>> does not mean that a "zillion" amp 5V power supply could not be under
>> voltage. You need to check the voltage at the board with a good digital
>> meter. Another important consideration is that the dynamic change in
>> current of the board when heavily processing vs. idling can vary greatly.
>> If the supply cannot handle these extremely fast current changes it could
>> signal an under voltage condition. The wall wart you used to power your
>> Pi2
>> or Pi3B may not cut it for the 3B+ especially in turbo mode.
>>
>> I have had good success so far with wall warts BUT I consider myself
>> lucky.
>> I run 10+ Pi's with outlet strips full of wall warts. Ultimately this is
>> probably not the way to go as besides the fact they can cause power
>> problems they also emit a lot of RF noise. A better way would be to use
>> the
>> 12V to 5V 3A modules and run everything from a good 12V supply fusing the
>> 12V input at each module. Here are a couple of examples. There are many to
>> choose from on Ebay.
>>
>> https://www.ebay.com/p/Car-Buck-Converter-Step-down-Power-
>> Supply-Voltage-Regulator-DC-12v-to-5v-3a-15w/19011441481
>>
>> https://www.ebay.com/itm/SUPERNIGHT-DC-DC-12V-24V-to-5V-3A-
>> 15W-Converter-Step-Down-Power-Regulator-Module-/392044239513
>>
>>
>> *73 Doug*
>>
>> *WA3DSP*
>>
>> *http://www.crompton.com/hamradio <http://www.crompton.com/hamradio>*
>> _______________________________________________
>>
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>>
>> Visit the BBB and RPi2/3 web page - http://hamvoip.org
>>
>>
> --
> 73 Jim
> La ciruela de Panamá
>
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