ESP8266 Community Forum

- Wed Mar 09, 2016 8:11 am #42751 ok, a bit of an update.

I got my new weather sensor (BME280) it's really good, works great at low voltages and does temp, humidity and pressure. So I update my circuit to use a 1N4001 diode with the 4.2v battery and its back to being unstable again. Sometimes it boots, sometimes it crashes whilst trying to connect to WiFi. To ensure I haven't changed anything I connect the battery bypassing the diode and its fine. This is with a 0.uf ceramic, 1uf tant and 470uf.

I thought most of my previous problems were the regular not being able to cope with the sudden change in draw, but do diodes suffer from the same issue? It seems worse than the regulator.

- Wed Mar 09, 2016 11:03 am #42759 Try putting a meter on the power supply before and after the diode, carefully with the esp turned on, then you can really see what the voltage is. The BME280 draws in the 70µA range, so unless it is on a board with a high overhead I don't think it is a problem. The 1N4001 diode datasheet says up to 1.1V drop, if the meter says it is dropping too much try a Schottky diode, it should drop the voltage about half of the 1N4001 (Drop on 1N5817 is .45V at 1 A) according to the datasheets. Reality may be a bit different though.

I have a setup which is pretty close, 3.7V 500mah Lipo with a small solar cell, Olimex Esp8266 Dev board, Dht22 and DS18B20. I have a Schottky diode on battery Vin and Solar out, it has been running about 3 weeks like this, wakes up every 10 minutes checks in and shuts off. With no deep sleep the 3.7V Lipo powers it for about 3 days. The ESP ADC says the battery voltage stays at 3.9v +- .2v but I don't think it is 100% accurate. It needs more testing and maybe adjustment on the formula, but I was shooting for 10% on the resister divider to make it easy.