I am using:
1. Adafruit Universal USB / DC / Solar Lithium Ion/Polymer charger
2. Lithium Ion Cylindrical Battery - 3.7v 2200mAh
3. Sparkfun 9W Solar panels
to power an Adafruit ESP32-S2 TFT Feather.
If I charge up the battery and connect it all up, it works as expected. I am running the factory-installed ESP32-S2 TFT Feather program, so I can see the battery level slowly go down on the TFT screen. Eventually, it dies. However, no matter how much sunlight the solar panels get and how charged up the battery gets (back up to 4.2V according to a multimeter), the Arduino won't come back on. If I unplug and re-plug the Arduino, then it turns back on. But it won't come back on itself. Is this the expected behavior?
Full disclosure, I first posted this question over at the Arduino forum - a bad habit of mine. One suggestion was to use a "reset supervisor of some sort". This seems slightly more complicated than I'd like to get, so I am hoping there is another answer.
The other suggestion was to post here. So, here I am.
Thanks in advance.
Universal Solar Charger - Arduino recovering after low power
Moderators: adafruit_support_bill, adafruit
Please be positive and constructive with your questions and comments.
- jeffcrouse
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- adafruit_support_mike
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Re: Universal Solar Charger - Arduino recovering after low power
Yes.
The ESP32's brownout detector will put the chip in a deep low-power mode that only wakes up in response to an external signal. The possible wakeup sources are listed in section 31.3.10 of the ESP32 Technical Reference Manual:
https://www.espressif.com/sites/default ... ual_en.pdf
In practice, it will be easier to use a voltage monitor like the KA75330 connected to the Feather's EN pin:
https://www.adafruit.com/product/3428
That will shut the Feather's voltage regulator down when the input voltage falls below 3.3V, and only turn the regulator back on when the input voltage rises to about 3.35V. That will give you clean shutdown and startup behavior as the battery discharges and recharges.
- jeffcrouse
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- Joined: Fri Dec 21, 2012 8:38 pm
Re: Universal Solar Charger - Arduino recovering after low power
This is the missing piece I was looking for! Thank you. I will try it out and report back.
- sj_remington
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Re: Universal Solar Charger - Arduino recovering after low power
Notice that the KA75330 is a reset controller (reset supervisor), as was suggested on the Arduino forum to use.
- jeffcrouse
- Posts: 22
- Joined: Fri Dec 21, 2012 8:38 pm
Re: Universal Solar Charger - Arduino recovering after low power
"was suggested" -- hahasj_remington wrote: ↑Mon May 08, 2023 12:36 pm Notice that the KA75330 is a reset controller (reset supervisor), as was suggested on the Arduino forum to use.
thanks, sj_remington. I was hoping to hear that I just hadn't connected something properly, but I never discounted your suggestion!
I also prematurely declared victory on the Arduino forum... I'm about to try out the KA75330 now.
- jeffcrouse
- Posts: 22
- Joined: Fri Dec 21, 2012 8:38 pm
Re: Universal Solar Charger - Arduino recovering after low power
@adafruit_support_mike I got myself a KA75330 and hooked up the OUTPUT pin to the EN on the feather. But it still doesn't wake up.
I did a test (video) with just the KA75330 and my bench power supply and multimeter, and the output pin briefly goes above 0.01V as the input passes 3.7V. Is this how it's supposed to behave? I would imagine the Feather wouldn't even recognize that as HIGH. Am I doing something wrong?
I did a test (video) with just the KA75330 and my bench power supply and multimeter, and the output pin briefly goes above 0.01V as the input passes 3.7V. Is this how it's supposed to behave? I would imagine the Feather wouldn't even recognize that as HIGH. Am I doing something wrong?
- jeffcrouse
- Posts: 22
- Joined: Fri Dec 21, 2012 8:38 pm
Re: Universal Solar Charger - Arduino recovering after low power
I'm still having trouble figuring this out and would really appreciate any help anyone could offer.
- adafruit_support_bill
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Re: Universal Solar Charger - Arduino recovering after low power
The KA75330 has an open collector output, so it needs a pullup resistor for the pin to go high.
The EN pin on the feather already has a pullup resistor on it, so no need for an extra component when using the KA75330 to drive that.
The EN pin on the feather already has a pullup resistor on it, so no need for an extra component when using the KA75330 to drive that.
Please be positive and constructive with your questions and comments.