[arm-allstar] Adventures with RPi3 5V power

[Chris Viningre]

Very useful information. Thanks David.


On Dec 23, 2017 2:12 AM, David McGough via arm-allstar <
arm-allstar at hamvoip.org> wrote:

>
> Hi Everyone,
>
> Since the question of what power supply to use with the RPi3 is a regular
> question asked on this list, I thought I'd post some results I've
> obtained, including real photos of live operation.
>
> After a quantity of experimentation, I've adopted the cheap high-frequency
> 5 volt, 3 amp buck-mode DC-DC switcher as the ONLY power supply (PS) I
> use.  In addition, for all my "production" systems (including repeaters,
> remote base radios, etc.), I SOLDER the power leads to the RPi3 board--see
> the photos below as for why I adopted this method.
>
> Here is an example of this PS: https://www.ebay.com/itm/173040030132
> ....the "Micro USB(Model 1)" version. I set my bench power supply to 10
> volts, for easy power calculations.
>
> For ALL these tests, I connected the RPi3 boards to the network via WiFi.
>
> Here is the RPi3 board with a fob and Asterisk/app_rpt running. Note the
> input power is about 10V * 0.17A = 1.7 watts. The measured USB voltage is
> 4.96V. See: https://hamvoip.org/photos/RPi3-usb-unloaded.jpg
>
> Here is the same RPi3 board which additionally has the CPU "maxed"
> out doing an intensive parallel compile of Asterisk on an NFS mounted
> filesystem. The input power is 10V * 0.42A = 4.2 watts. BUT, also note
> that the USB voltage has DROPPED 0.1 volts! See:
> https://hamvoip.org/photos/RPi3-usb-loaded.jpg
>
> Now, we move to an example with a RPi3 which has a soldered-on power
> supply--one of the same style 5V 3A switchers as above, the only
> difference being leads for the output rather than a USB plug.
>
> Again we have an RPi3 board with a fob and Asterisk/app_rpt running.
> Note the input power is about 10V * 0.16A = 1.6 watts. The measured USB
> voltage is 5.04V. See: https://hamvoip.org/photos/
> RPi3-soldered-unloaded.jpg
>
> And, the same soldered RPi3 board which additionally has the CPU "maxed"
> out doing an intensive parallel compile of Asterisk on an NFS mounted
> filesystem. The input power is 10V * 0.42A = 4.2 watts. But, notice that
> the USB voltage is still 5.04 volts! Wow! No voltage drop under load! See:
> https://hamvoip.org/photos/RPi3-soldered-loaded.jpg
>
> So, my reasoning for soldering is simple: the micro USB plug may not be
> long-term reliable in an unattended, non-thermally-controlled repeater
> cabinet.  Here is a photo showing how the leads are soldered to the RPi3
> board: https://hamvoip.org/photos/RPi3-soldered-power.jpg
>
> Here is one of dozens of ebay listings for leaded PS units. This is the
> exact PS seen in the photos: https://www.ebay.com/itm/261335563607
>
> Using these PS units, soldered connections and WiFi, I've found RPi3
> boards to be at least as reliable as embedded PC computers.
>
>
> Merry Christmas and Happy Holidays!
>
>
> 73, David KB4FXC
>
>
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