Hey all,
I’m building a Raspberry Pi Zero based camera controller with integrated LiPo battery. Due to the fact that I am hotshoe mounting this, Im trying to make everything as small as I possibly can.
The last piece in the puzzle is that I want to read the battery voltage so that the Pi can be shut down nicely and Users warned that this is going to happen, so need an ADC to read the voltage.
I like the idea of the Gravity: I2C 3.7V Li Battery Fuel Gauge, but could do with something a little smaller if possible.
The un-rendered box on the right is this Gravity board.
It only JUST fits.
Does anyone have any alternative suggestions on how to read a voltage on the Raspberry Pi Zero by utilising the smallest possible package?
Oh and I wasn’t really intending on building a custom PCB or doing a lot of hand wiring on this project, trying to keep it ‘modularised’ as much as possible, however I am open to changing my mind on that if there are any elegant solutions.
THANKS!
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Hi Andrew,
That’s a great render of your build in progress, thanks for sharing it.
Usually, if someone just wanted to add an ADC to a Pi zero I’d recommend one of the I2C ADCs for simplicity but even those are going to possibly be too large for your build. This is the smallest one I can find.
Other options get very custom-built using something like an ATtiny but the DIP package would wind up around the same size as the I2C ADC.
If you were to custom-build something I’d look into what chips are used in our ADC breakouts then look up the datasheet and any application notes you can find for those chips.
For the example of the MCP4725 chip the datasheet has example circuit layouts from page 34 onwards under the heading 8.5 Application Examples, these will show you how to build your own breakout board if you want to go for a fully customised solution.
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Hey Trent, thanks for the fast reply.
Unfortunately the MCP4725 is a DAC, not an ADC, so no good 
I am open to, even though I did kinda say that I wasnt, creating a custom PCB, but I’d have to build out that board as a LiPo charge controller and DC Boost board and ADC in one.
That’s not beyond the scope of this project, but is beyond this first prototype.
FYI here’s the finished case render.
Software is almost done too, just finishing up the final interface, but, basically, this little hotshoe mountable product runs on a Raspberry Pi Zero, hahahah yeah like they are still available, right, and can control virtually any Nikon or Canon camera via USB.
You can connect to the Pi via the included WiFi Hotspot and do the following:
- Set camera Mode
- Set ISO
- Set Shutter Speed
- Set aperture on supported lenses
- Preview a shot and view remotely on phone or iPad or computer over WiFi
- Setup and run a timelapse with variable numbers of shots and timing between shots
- Setup and run a multiple shot Astro Imaging sequence with number of shots and length of shot and timing between shots
- In a timelapse use our custom Auto Exposure control to keep the exposure where you want it to be, allowing for Day to Night and Night to Day timelapses.
- All run from one 18650 LiPo that lasts at least 1500 shots in a timelapse over 5 hours.
- Charge the 18650 from an external battery while in use to give unlimited run time.
I’m close to being able to document a how to guide and will post it when finished.
So, yeah, space is of concern.
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Hi Andrew,
Oh good catch, we’ve got a couple of breakout boards that incorporate both so I mustn’t have been reading carefully enough, glad you picked up on my error.
Since the process outlining how to design a breakout board for a given IC still might be helpful to others on the forum I’ll leave my post above largely unedited.
I’d agree with your approach of avoiding as many custom-built PCBs as possible when working on version one of a design. Miniaturisation will probably call for it eventually but getting the whole system working in a too-large form factor first is incredibly valuable and will probably point out something that needs to change before you get too far down the rabbit hole.
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