switch 220V with a microprocessor

Billy_w

Hello all,

I would like to ask how one can switch on and off a device connected to 220 V using one microprocessor output (5V). I know I should use a relay but can I use only one relay, or a cascade of two relays? Any suggestion for what type of relay I should use?

TIA,
Billy_w

karmicthreat

One relay on the hot side of the 220V line is sufficent. You will need a transistor to drive the relay though since I doubt the uP's port has enough current capacity to drive it.

Integral

Look into solid state relays (SSR), one of these will eliminate arcing and the resulting contact corrosion.

NoTime

Might want to look into X10.
All set up to do this.

chroot

You should probably use a contactor rather than a relay for such high voltages. A simple power MOSFET is all you'd need to drive it with a 5V uP signal.

- Warren

Averagesupernova

Someone mentioned switching the hot side of the 220 volt line. In the U.S. BOTH sides of the line are hot on a 220 volt circuit. There IS no neutral. A clothes dryer for example is a 220 volt device and technically has a neutral because the motor runs on 120 volts. But a 220 volt device such as a water heater has NO neutral. There is a 3rd wire run but it is a ground and is not meant to carry current. In your case it is advisable to switch both of them regardless of the device used to switch.