Seeeduino Mega 1.23 to 5V power supply

I’m integrating a Seeeduino Mega 1.23 into a larger system that includes a regulated 5V power supply.
How would I bypass the Seeeduino Mega’s own regulator and power the board from an external 5V supply?

First, will it work to feed 5V and GND in through the 0.1" header?

Second, I would actually rather not tie up those header sockets. Is there a good place on the top of the board I could solder directly to feed 5V and GND into the board?

I’m not entirely clear on how the power manager circuit (in the v1.23 Eagle file) functions, so I don’t want to start plugging 5V without some design guidance.



mega is a small board that did not have any space to add and power supply socket , and it may damage the my opinion , perhaps used the white socket is a good idea .


Thank you for your thoughts Deray.

I’m not worried about hurting the board by soldering a wire or two into the power management section.
I am cognizant of hurting the board by applying 5V in the wrong place! :slight_smile:
The “white socket” power connector feeds into a 1117-5 low dropout regulator, whose datasheets specifies 6.5V<=Vin<= 12V, so applying 5V there will not work.

Maybe on the OUT terminal of the 1117-5 might be a good place to feed in 5V.

I’m just not clear on the functioning of the “gate” signal from the LM358 to the MOSFET.


maybe you can used the “5V”“GND”pin , the mega can be drived when 5V power supply. or connect jumper wire to the “VCC”“GND” of USB port .

Thank you again Deray.

Are you a fellow user or do you work for Seeedstudio?

When you say “MAYBE” I can use the 5V”“GND”pins, are you sying that you know this for a fact from an engineering standpoint? Or are you just brainstorming?

I do not perceive from your responses that you are familiar with the power section of the Seeeduino Mega 1.23.

I am looking for (A.) an explanation of the functioning of the 1117-5, the LM358 and the MOSFET
and (B) a recommendation where I can tap into that circuit to apply regulated 5V directly to the board, without using the Arduino 0.1" 5V and GND header, nor the USB jack.

Thanks again,

yeah ,I really don’t familiar with the power section of the Seeeduino Mega. My proposal because I had done supply 5V voltage on that pin , the Mega work right .
Furthermore,about your question , I will ask our engineer to answer .Thanks for your comprehend.


You can Solder the 5v to the C8 it just near the USB connector.
Easiest way:
Connect your Extern 5V(<2A current) to Highlighted Square Pad, GND to Round Pad.
But note, this application is connect your extern 5V to USB 5V, it may burn your PC USB.

Safe way, but solder needed, do not plug the extern power to the JST connector(6.5~12V DC).

  1. connect extern 5v to the Highlighted pad and LM358 pin 3.
  2. connect GND to GND.

The LM358 and Si2305 are use to protect the USB while Extern power is plugged.
And need give LM358 pin 3 larger than 3.3v(5v is OK) to isolate USB power to system.


I want to power my Seeeduino mega V3.0. with an external 5V source while the USB is still connected.
Posts below explain this for version 1.23 but does anybody know how this can be done using a Seeeduino mega V3.0 board?

thanks in advance,