ardino as the pwer source

Hi,
I just obtained an Arduino Duemilanove board.
I'm novice in electronics. I just did a tutorial to control a servo motor. In the tutorial, the PWM is connected to 7th pin of the digital inputs. The servo motor ground and 5v are connected to the power slots on Aurdino using pins.

My question is, that if I want to power 2 servo motors from aurdino board, what is the best way to do that? just power them in serial? doesn't it hurt the device?

Thank you,
Sm. :slight_smile:

That depends on how current your servos require. Try it with both servo power wires (the center wire) both connected to +5volts on the Arduino board.

If the servos don't function correctly when they are both moving at the same time then you may need to power them from an external 5 volts power supply.

If using an external supply, the servo power leads connect to the positive side of the supply, the grounds of the servos connect to the power supply and to the arduino ground.

Thank you, I got the idea. But what about the safety matter? Can I just simply power the devices (sensors, servo and so on) to test if they function or not? In case of the high power demanding device, it does hurt the Aurdino doesn't it?

it does hurt the Aurdino doesn't it

No not if the power is within limits. See:-
http://www.thebox.myzen.co.uk/Tutorial/Power_Examples.html

Also if you are using motors you might need some extra de coupling:-

http://www.thebox.myzen.co.uk/Tutorial/De-coupling.html

I really like your tutorials Mike, but they may be more info than the OP can use in this case.

Its almost impossible to calculate the power drawn from a servo under load without some sophisticated equipment. IMO, its generally safe to connect two hobby servos to the arduino 5v line. The power supply should shut down in the event that too much power is being drawn. But its prudent to check the arduino voltage regulator is not running hot to the touch when running things like servos.

In my experience , hobby servos include sufficient decoupling that they should not need much in the way of extra decoupling to work with the arduino.

Its almost impossible to calculate the power drawn from a servo under load without some sophisticated equipment.

I usually go by the motor/servo stall rating and make sure the source can handle that. This way if something goes wrong mechanically I don't over draw the source.