Question of using external power supply for Arduino Micro


I am developing a project by using Arduino Micro, and for some reason we can not use the USB port or the battery to power the Arduino Micro board. The power supply for the system will be a DC adapter whose ratings are 12V 10A. I am just wondering if 10A is too much for the Micro board to take, I realized that all the external power supply needs to go across the pin of "Vin" and "GND".

I really appreciate if anyone who has similar experiences can tell me what to do with this.



The board will only draw the 30-40mA it needs to operate. The onboard regulator will get warm knocking 12V down to 5V. As long as you're not connecting lots of LEDs, motors, etc. to the 5V pin you will be okay.

If 12 V is what you have available, use a DC-DC converter to lower the voltage to something like 8-9V so that it wont heat up the on-board regulator.

You can use something like this

As CrossRoads said, it all depends on what you connect to the Micro.
With nothing connected to it, the regulator uses 12-5=7volt x 35mA = 250mW.
Nothing to worry about.

Tell us what you are going to connect to the Micro.

The current rating of a power supply is only what the power CAN supply not what it WILL supply.

Hi, Everyone

thanks for the quick reply you guys gave me.

Actually I am connecting a replay and a couple of LEDs as indicators to the Micro board, and I am using the relay to control a 100 Watts heater, the heater will share the same power supply and this is the reason why I want to use this high rating DC power supply to power the Micro board. So do you guys think if the power will burn the micro board in this case?

thanks for your help.


"The power supply for the system will be a DC adapter whose ratings are 12V 10A"

When you say an adapter, does that mean it is to charge 12 volt batteries, or it actually puts out a regulated 12 volts.

If it is to charge batteries, the voltage will be higher than you may expect.

If you are unsure, put a voltmeter on it.

As jack wp said, if the supply is not regulated you could be in trouble.
An unregulated supply could be a lot more than 12volt when the heater is off.
Post a link to the supply.

If you use a 12volt relay board, and power the coil directly from the 12volt supply, then there will be no extra load on the Micro.
How many is "a couple of" LEDs.

There is already an indicator LED on the relay board.

So do you guys think if the power will burn the micro board in this case?

Did you read reply #4?

I think he's talking about the heat from reducing the (likely 14 volts or more) power supply voltage to 5 volts with the on-board regulator. It is likely to get hot, especially if it's running at a higher voltage. The micro can stand up to 20v for a short time, but it should be less than 12 (ideally about 7.5ish) for continuous running.

So the answer is yes, running an Arduino micro in continuous operation at greater than 12 volts can indeed "burn the micro board". Well, not burn, but shorten it's life from where it would have been if the voltage were kept lower.