ESP8266 Community Forum

- Wed Feb 17, 2016 4:45 pm #41309 I have been going mad trying to get an ESP-12E running from a 18650 battery. It's a simple circuit that reads from a DHT22 and posts to Thingspeak. Ideally I didn't want to run directly from the battery as the 4.2V is over the recommended value, although I have run it from the battery and all is fine.

The issue is when using an LDO. I have tried using various LDOs, MCP1700 and MCP1825s which is rated at 500mA. Neither of these are stable enough. Looking at the serial output I get all sorts of crashes, memory dumps and resets when powering up. I am using the caps recommended on the spec sheets for the regulators, and I tried placing in 470uf cap and 1uf decoupling cap close to the ESP vin/gnd pins. These helped, but still not completely stable, but still sometimes fails to boot or resets when connecting to wifi. This is in a breadboard if it makes any difference.

Any ideas? I am at the point where I will probably just run it straight from the battery as I am so fed up

- Fri Feb 19, 2016 9:18 am #41452 If you can find a LM3671 (adafruit has a breakout board) try that. I have been using that with 3.7 Lipo and it works well so far. I don't think the MCP1700 puts out enough current, and the MCP1825s says input from 2.1 to 6 V output from .8 to 5 V. I kind of wonder when the data sheet says min input 2.1 V, Min output 0.8V and dropout V of 350mV ish. They calculate dropout as Vin - Vout, to me it looks like it could be more than 350mV but I don't know. I like data sheets that list the specs for each of the fixed voltage models, not a range for the line.

If you have 4 Nimh and a battery holder try that with the MCP1825s, and check the output voltage with a meter. Also check the battery. I have read there are a lot of bad (mislabeled at higher mAh) 18650 batteries around. I have run a ESP12E on 3 Nimh batteries and no regulator, but I do not recommend it at all, it is more than it is supposed to take.

And, be aware there are a lot of bad breadboards out there. I wish I could find a good one, but all the breadboards i have purchased are horrible. Everything must be perfectly aligned or is doesn't work. When I started with the ESP8266, that was the most frustrating thing.

- Fri Feb 19, 2016 11:21 am #41465 I've had no problems using a MCP1700 and a 1200mAh phone battery (no caps).

A not-quite-perfect alternative is to put a diode in series and drop the battery voltage by 0.6V. Of course this will put 3.7V across the ESP when the battery is fully charged to 4.2V, but is probably fine for hobbyist use.

- Fri Feb 19, 2016 5:21 pm #41482 I agree with what you say on the spec sheet for the MCP1825s, it is hard to tell the exact specs for the fixed rated versions.

Anyway, I have made a few changes. I now have a 0.1uf ceramic and 1uf tantalum as decoupling caps for the ESP. Seems to be working fine now without needing a big 470uf cap I did have in before, although I will probably put the 470uf back in the final design.

I think it might well be the breadboard that has caused many of these misleading problems. It seems very temperamental, where as if I hold the wires firmly still it all seems good. I think I will just solder it up now and see how it goes.

I too would like to find a decent breadboard, all the ones I have are pretty nasty.