Turn off Charge Function on 32u4 Datalogger?

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jacobfister
 
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Turn off Charge Function on 32u4 Datalogger?

Post by jacobfister »

Hello, I have a project using the 32u4 datalogger and I'm using a small LiIon cell as a backup battery so using the on-board charging circuitry is fine.

I also want to use a separate charging circuit and battery system (on a different version of the same project) (still 1S, so 3.7V) that has its own charge circuitry. Can I still plug in the cell voltage to VBAT so I can get a reading of the battery level with the controller, even though I don't want to use the charge circuitry on the board? Is there a way to disable the boards charging circuitry? The problem I foresee is the two charge circuits trying to charge the batteries at once. Would this be solved with a diode allowing voltage TO the feather board and not FROM the feather board via VBAT? Seems like a brute force solution but if it works, it works.

I would use a different board type but I'm trying to make the motherboards I'm designing as modular as possible, and not needing to use a different board for the two versions (integrated and separate charging/battery circuits) would be nice.

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Franklin97355
 
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Re: Turn off Charge Function on 32u4 Datalogger?

Post by Franklin97355 »

Do you need the USB connection on both processors? If not there may be a way. If you do then I'll have to ask other techs about it.

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jacobfister
 
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Re: Turn off Charge Function on 32u4 Datalogger?

Post by jacobfister »

Not necessarily. It would be a "nice to have" but the idea is that one would be a mobile version (the one with the larger battery cells and separate charging circuit) and one would be a bench version (the one with just a small backup battery connected to the JST port on the feather board). I COULD sacrifice connectivity/serial output on the mobile version if I needed to. I was also thinking since I made the first post that it could possible hook a transistor up to the VBUS pin through a NOT gate to disable the charging from the standalone charger when the feather is hooked up to USB? (sketch attached) It seems like it would work, but I might need some sort of cap in there to prevent any sudden voltage changes on the VBAT line.
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adafruit_support_bill
 
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Re: Turn off Charge Function on 32u4 Datalogger?

Post by adafruit_support_bill »

One solution would be to simply cut the +5v VBUS wire on a USB cable to use when you need USB communication. That will give you the USB data connectivity while avoiding any battles between the voltage regulators.

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