Using digital outputs to switch 24v DC

Using the arduino digital outputs can someone tell me what circuit I need to switch 24v DC on/off. Each 24V line will only be using 50mA and I have a 24v DC power supply. I need 4 independant channelsor devices to control some pneumatic pilot valves. An RS component code would be a perfect answer.

I know it's a simple electronic question but I'm good with mechanisms rather than the electroncis behind them lol

regards Kev

Most of the relay circuits that have been posted will work on 24 volts, such as this one: http://www.arduino.cc/playground/uploads/Learning/relays.pdf

wow I didn't even know that the playground existed, that should stop me looking like a newb for awhile lol

thanks for the prompt response :)

Kev

I think a chip such as the ULN2803 would be a good choice. It's rated for up to 50V switching, at 500mA per channel, eight channels.

Thank you for the suggestion

Would this system work with 12V at about 5 A.? I want to control some wiper motors with the arduino board.

The ULN2803 is limited to 500mA per output. You'd need something rather larger to switch 5A. Maybe a power transistor or power MOSFET?

Some circuit suggestions for higher-power switching (without relays) are here.