Solar BOD brownout overnight

Hi, i am a software developer who has installed a nice LoRa setup inside home, but...
Now it's time for the garden! :slight_smile:

I already have a plant monitoring setup using AtMega328P with it's solar panel, it's CN3065 circuit and it's 3,7v battery, all ok?

PROBLEM!
Some nights the battery empties, and starts charging when sun raises, but the voltage to the microcontroller rises slowly, so it halts due BOD 'brownout' protection. So, i have to go out and push reset button :frowning:

Does anybody know any easy solution ?
Maybe a diy circuit for makers?

I would appreciate help.

Thank you very much

I, after about a year, gave up on LiPo for solar.

I switched over the PWM Charge controller and a LiFePo4 battery.

With that said, I got the best operational LiPo battery life from using a 3.3V regulator to supply the MCU. The 3.3V regulator has a shutoff volts which did the trick for me in powering the project back up without needing to press the reset button.

The battery is falling below the MCU operational volts, so the MCU shuts off. Whiles off the battery recovers and begins to supply power to the MCU. The battery, being weak, voltage falls off, shutting off the mcu, till the battery recovers again. 6 to 8 hours of this and the battery charge gets severely depleted and has its life shortened. The addition of a regulator helps lower the occurrences of the destructive cycle.

This is an brownout circuit from when they didn't build it in.

I don't know how it works, it is supposed to hold reset until the Vcc is high enough… perhaps someone here can validate and explain or debunk it. Which (debunking) would mean I've wasted a few 2N3906s around the house.

HTH

a7

There are power supply supervisor ICs, TC54 etc, that could keep the reset line of the processor low until the battery rises to a particular value, 3.3V for instance.

Available in a range of voltages, in SMT or T092 packages.

This project has a circuit that delays startup of the micro, using a MAX8881, until the voltage is up and sufficient is stored in the supply capacitors. This circuit actually controls the supply not just the reset pin.
Remote Controlled Light Switch

You may find some ideas in Nick Gammon's article on a solar powered Arduino, which uses a supercap instead of a rechargeable battery.

As has already been mentioned, 3-pin voltage supervisor ICs are designed for the reset task. Microchip's MCP130 series and TC54 series are good.

Wow!
Such quality, much answers :dog:

Sadly, i am a software developer, my electronics knowledge is really poor :pensive:

May try PWM Charger, doesn't require custom electronics.