Batterieüberwachung, voltage divider und attenuation für MicroPython-Firmware

[Andreas]

Late or not, I wanted to share appropriate pointers to the Pycom forum anyway.

• ADC use to measure battery level / Vin level | Pycom user forum

---

Best comment - as always - by robert-hh from Pycom forum:

robert-hh
Jan 31, 2019, 7:07 AM

Explanation

The maximum range of the ADC when using the 11dB attenuation is 0-~3V. A Li-Battery has a voltage of up to 4.2V. So you need a voltage divider. And then it does not matter whether the range at its output is 0-1V or 0-3.3V.

Recommendation

So, take a resistor pair of 1MOhm (to battery) and 220kOhm, dividing by 5.4545, and use the basic range. Add a small capacitor at the ADC input to GND to have a low impedance for the moment of sampling. That divider will draw a constant current of 2.5µA. If that is too much, you’ll need a p-type MOSFET to switch the divider off when not needed.

Das liest sich für mich wie eine Empfehlung für eine Referenzimplementierung. Die Widerstandswerte entsprechen den von @didilamken vorgeschlagenen.