I have setup two ESP32-CAMs, sharing the signal from a PIR sensor via an optocoupler.

Plus I have a 12V LED ring on a 5V to 12V booster, turned on/off by a relay.

The ESP32s go to deep sleep, wake up on the signal from the PIR sensor, turn on the 12V IR LED ring, take some photos and go back to deep sleep.

When they are on three separate power circuits, they seem to work well.

Is it safe to connect all these to the same USB output from an USB power bank?

Or can it be done safely at all?

(Could be similar to this question but I'm not sure.)

I am new at this and I don't have any intuition about whether that would create odd voltages and currents that might damage the components on the long-term, as they keep turning on/off and draw varying amount of power.

Instead of three USB connections like this:

(trying to illustrate only the power circuits)

three usbs

I would like to power them on one USB connection:

one usb

1 Answer 1


There is no difference between your circuits. Internally to the powerbank all three outlets are typically wired together just like in your second schematic. One outlet or three outlets it's all the same.

  • I plugged in a multimeter and tested different configurations. In both cases the current only jumps up to ~150mA which is ok for the esp32. But on one battery USB output, the voltage dips down to 3V as different parts turn on/off, that's too low for the esp32 and it becomes unstable. Adding 4x100uF caps across the power rail didn't help. When they are on separate battery USB outputs, the battery maintains a steady 4.8-5V. I guess there's not much I can do about it, they have to be on separate outputs.
    – Gambhiro
    Apr 29, 2022 at 19:56
  • The LED ring is an FY-530, the specs say 200mA. I didn't see a voltage dip when it turned on, perhaps that part is ok. The problem could be that the two esp32 circuits on the same power source act as a voltage divider? Is there a technique to prevent that? The power bank seems to deal with it somehow, as they are designed to charge two or three phones etc. at the same time.
    – Gambhiro
    Apr 30, 2022 at 6:13
  • 1
    @Gambhiro Things in parallel don't divide the voltage, they divide the current. Maybe there is a mistake in your wiring.
    – Majenko
    Apr 30, 2022 at 12:25
  • Thanks for the comments, I'm sorry about the clueless question. A proper question would probably have to approach ESP32 power supplies in general. Perhaps it would be best to delete the question.
    – Gambhiro
    May 1, 2022 at 5:53

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