I have an arduino board which I want to use to give power to a device which uses two 1.5V batteries. I think I have to remove the batteries from the device and control the power supply via arduino, but since I have never did this, I'm asking which is the best way to do this.
How would you use arduino to give power to an external, battery powered device?
* Adding details *
I want to power an electro thermoregulator of my house. I have the arduino controlled with a GPRS module, and everything is working fine. The only point left is how to use the arduino to give power to that device.