[nSLUG] Powering a RPi (was Re: Cellular dongles)

Joel Maxuel j.maxuel at gmail.com
Mon May 27 13:44:01 ADT 2019


Considering what I plan to attach to the RPi, I will want to ensure all the
power I can get:

>
>> - Two Phidget InterfaceKits (an 8/8/8 and a 0/16/16)
>> - A RaZberry2 (https://z-wave.me/products/razberry/)
>> - The E303 cell dongle
>>
>> What complicates the situation is that the RaZberry sits on top of P1
>> (covers the top ten pins) although there is a spot on the RaZberry to
>> solder on another header to use those ten pins covered:
>>
>>
>> https://raspberrypi.stackexchange.com/questions/11787/would-it-be-possible-to-use-both-a-razberry-z-wave-and-a-raspbee-simultaneously
>>
>>
>>
>  As long as enough power can pass through back down to the RPi, it should
>> be fine.
>>
>>
> Another possibility if you have other requirements, would be to lay out a
> simple pass through PCB.  Adafruit sells stacking headers:
> https://www.adafruit.com/product/1112
>

 Interestingly enough, I discovered one of those conclusions earlier today
with the MoPi2 (paired with the stacking header):
https://pi.gate.ac.uk/pages/mopi.html

...which will allow up to 2.5A (given if each peripheral peaks at the same
time - that can still leave 960mA) for the Pi.


> And this way you could position your board between the pi and Razberry2.
> You could break out the supply pins, and any other peripherals for any
> customization you need (UART, I2C for realtime clock....).  It's pretty
> cheap to get PCBs made up at OSHPark and if you have a couple random
> circuits, it can greatly clean up your project.  When you're getting
> closer, I'd be happy to show you enough KiCad to make you dangerous.
>

Not sure how important that detail will be, as the finished product will be
in my basement (likely mounted to the wall in a panel box).  You mentioned
breakout for an RTC - is internal time-keeping that bad, or just plain
non-existent?

Additionally, I would want this battery-backed as I will be using it to
>> send a notice in the event of a power loss.  I could use an existing UPS,
>> but avoiding additional power conversion (battery DC to wall wort AC back
>> to DC for the RPi) would make more sense here.
>>
>> I will eventually (in some years[1]) have a 12VDC lead-acid bank to work
>> from, so my interim solution should be setting up something that will be
>> easy to adapt to that as well.  (Or, since I need to add a marine
>> battery[2] to the basement next month anyway, maybe I should run a couple
>> wires and adapt from that?)
>>
>>
> I've seen several boards go by which are a UPS integrated right with the
> Pi.  It avoids the inverter making AC just to turn it back into DC
> problem.  Also, most inexpensive AC UPS' I've seen put out really dirty
> power that you might not want to subject your delicate electronics to.
>
>
> https://www.buyapi.ca/product/ups-pico-uninterruptible-power-supply-i2c-control-hat/
>
>
> https://uk.pi-supply.com/products/pi-ups-uninterrupted-power-supply-raspberry-pi
>
> I have no direct experience when any of these, but might work for you.
>

That would probably be a more practical solution, as my current backup
power solution includes a subpanel for "life-support" circuits, one of
which feeds the core networking (and the RPi will be a part of that).
Although there can be more flexibility for never having to shut down to
power shortage, my subpanel (generator-fed currently, option for
solar/reserve some later time) limits that time anyway.
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