Is possible when i connect 2 power source simultaneously

Is possible when i connect 2 power source simultaneously: adapter 9VDC and power bank 5VDC (micro usb port) to ESP32 D1 R32 Wemos. If it's possible, which power has priority? Thanks

That depends on how that board is made.

The Arduino Uno is specifically made for that situation. When the power at the barrel jack drops below 7.5V, then the USB power is turned on.

Could this be a schematic of that board ?
I think it can be powered with the barrel jack, the 5V pin and the USB connector.
The priority is hard to tell.

Can you power it with only the barrel jack and measure the 5V pin ?
Then power it with only the power bank and measure the 5V pin.
The one with the highest voltage has the priority. Since there is a voltage drop in the USB cable, I assume that the barrel jack wins.

The schematic for the ESP32 D1 R32 Wemos board that Koepel has shown is typical for an ESP32 board and does have the ability to connect both barrel jack and USB power simultaneously. The barrel jack (9VDC adapter in your case) takes priority, as when it is connected the op-amp (RC1K) and MOSFET (A1SHB) shown in the schematic disconnect power from the micro-USB connector.

many thanks


By the way, there is an error on the diagram. If the FB pin of MP1482DS is connected to the output of the converter by 47k, it will give Vout = 0.93 V.
Obviously there should be a 10k resistor between FB and ground. Then the output voltage will be 5.3 V.

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