Is a 12V/2A external power supply too much for my Arduino Uno?


I have this project (see blueprint) where is one servo motor: Hitec HS-5985MG ( First I used one 9V battery to power the system up, but there was not enough juice to keep it running. It only worked properly for a few seconds. Then I bought a compact 12V/2A external power supply , but it seems to get Arduino to warm up and after a few second the system doesn’t work properly.
The system is as follows: When you move in front of IR proximity sensor the servo motor cycles around, when you go away from IR the servo stops. That simple. The on-off switch gets the led on and the system is ready to do what it is supposed to do. When OFF, the servo doesn’t move.
So, is the 2 amps too much? Should I get a smaller amps power supply?

Thanks, Jarppa

A big part of the problem is that the Arduino probably can't supply enough current for the motor.

The 12v supply will be OK for the Arduino (there is no such thing as too many amps - it only uses what it needs).

You need a separate circuit from the same 12v supply to provide 4.8v to 6v to power the servo. A 7805 voltage regulator might do, but I think it can only supply 1 amp and that may not be enough for the servo. It should be OK for testing.

The Arduino ground must be connected to the servo ground.


The arduino regulates the voltage down to 5V, so if you have 12V it has to burn off the extra power. This is 7V times the current. So for 1 A this is the same as heating it up with 7W. That is too much heat.

One way to reduce this is to use a lower voltage, anything over 6.8V ( or so ) is enough for the regulator and drops the power burned up quite a lot. In other words if you got a 9V power supply it would not get as hot.