libre360
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localdevices
Battery solution + docs
A battery and connection scheme needs adding to the rig and documented.
Amen. Starting with this hub: https://www.amazon.com/gp/product/B0779D7DFG/. More to come.
And these are the cables I am starting with: https://www.amazon.com/gp/product/B00ENZDFQ4/
We do need a battery solution that is easy to carry around preferrably somewhere hidden in the 3d printed shell. Any clue what would be suitable?
Given the weight, I am leaning toward having the power supply inside a backpack separate from the cameras. As far as power, either a lipo or li-metal source would work well.
Also gonna put this in the mix. It's an optional component, but should give a little more protection in the case of a short: https://www.amazon.com/VIFLY-ShortSaver-Electronic-Short-Circuit-Available/dp/B088TVVNVM/
This means we probably want ~18-24 volts going in, so we can get the full 44 amps we need out at the 2amp ceiling of this short circuit protection. So a 5s or 6s battery is what we need, though I could use a vote of confidence from @ivangayton:
| Amps | Volts | Power |
|---|---|---|
| 2.4 | 5 | 12 |
| 2.4 | 5 | 12 |
| 1 | 5 | 5 |
| 1 | 5 | 5 |
| 1 | 5 | 5 |
| 1 | 5 | 5 |
| -- | Total Power | 44 |
Giving us:
| Battery Type | Minimum Voltage | Max power draw at minimum voltage |
|---|---|---|
| 6S | 22.36V | 1.97664 |
| 5S | 18.63V | 2.361782 |
Hmm, I'm worried about 6S—and even 5S—batteries being a hassle to procure and charge. If we stick to 3S, it's extremely easy to buy them, and in an absolute pinch you can use a motorcycle battery instead (or, if you're in a vehicle, use the onboard battery).
5S and 6S batteries often require more expensive and hard-to-find chargers.
So I'm very hesitant to move to a battery that's more hassle to manage just to accommodate the limit of a $10 circuit protector...
Admittedly, it's nice to have a sweet, fast circuit protector instead of a fuse, but I wouldn't say that's worth the cost of switching away from the 3S battery, which can be drop-in replaced by a huge variety of other things.
As for a sanity check:
Ardusimple with an xbee power draw ~200mA Pi zero power draw ~140mA Pi 4B loaded to the nuts power draw ~1280mA
7 Zeros ~1A 2 4B's ~2.6A 1 ArduSimple 0.2A
so about 3.8A altogether.
Double it for safety (and to account for the power loss in the adapter): 7.6A
At 5V that's about 38W.
38W at 12V = 3.2A
So indeed a 2A circuit protector on a 3S battery is not going to be sufficient (though these calculations include a fair safety margin).
We need 3.5A of protection, either a circuit protector or just a dumb 'ol fuse.
I did a similar calculation and came up with very similar numbers. The cameras consume a fair amount of current on their own, so I think the doubling is a necessary thing.
Nice thing is, we can offer options based on availability. I might have a 6s I want to use, but we spec the standard model for 3s.
6s for amperage is ready.
- soldering between 6s and usb rig needed, then goog-to-go
- parts list and instructions upcoming
OK, we are good to go for the first round. This won't yet power GPS, but as GPS integration isn't complete, this isn't an issue.
I'll also document an alternative build without the VIFLY ShortSaver (Smart Smoke Stopper), using a standard smoke stopper.
@ivangayton, I assume it's a bad idea to Y two 3S's together as an alternative to a 6S?