ESP8266 Community Forum

- Fri Oct 23, 2020 10:05 am #89175

The capacitor maximum voltage marking is this J in 106J, and it means that it is 6.3V ( https://www.electronics-notes.com/artic ... rkings.php )...

Thanks for that link, good to know. I measured the voltage across that that capacitor, and it is indeed the same as the voltage supplied to Vin pin. But in any case, NODEMCU is supposed to powered between 7V and 12V to that Vin pin. Anything below 7V just makes it unstable or not boot at all. So I'm not sure what's going on here.

- Fri Oct 23, 2020 10:35 am #89176 You might have been getting a higher voltage from the servo. The large capacitor might have been absorbing higher generated peaks. If you have an oscilloscope, look at what you get on the power line.

Maybe put a 100uF cap in place of the 2200uF for initial development. That might control some peaks but not be too much of a load.

- Fri Oct 23, 2020 10:42 am #89177

You might have been getting a higher voltage from the servo. The large capacitor might have been absorbing higher generated peaks. If you have an oscilloscope, look at what you get on the power line.

Maybe put a 100uF cap in place of the 2200uF for initial development. That might control some peaks but not be too much of a load.

That is what I'm suspecting, but I don't understand how the servo can be creating these peaks. Can you explain? And besides the capacitor, is there any other way of protecting my circuit from the servo without giving that servo a different power supply? Some diodes or something? Unfortunately I do not have an oscilloscope.

- Fri Oct 23, 2020 2:41 pm #89179 A NodeMCU should work OK from 5V up on the external Vin. It feeds the regulator just like the USB (with an isolation schottky). Although some NodeMCU may be able to tolerate higher voltages that will because they have a higher voltage capacitor fitted. It is still not a good idea to feed a linear regulator with a higher voltage than necessary as it causes excessive heat and will drain the battery faster.

If you are having to use a higher voltage then I would suspect that there is something wrong with the boost converter particularly around whether it can supply the peak current requirements of the NodeMCU which can go up to 500mA.

As I said feeding this from 5V may be better idea if this can give a decent current. It will also probably work direct from the battery at least when well charged. The on board regulator fitted is not the best from a drop out viewpoint so that would limit how far the battery voltage can fall.

A SG90 servo should only draw about 300mA when running. This should not cause any difficulty even on the same rail as the NodeMCU. I have several servo applications using MG90 (metal gear equivalent) and they power the servos from same supply with just simple decoupling.