[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):

...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

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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