pecu switch - where to find good one?


I would like to use arduino to make for my garage (outside) a system, that pecu switch would monitor if it is dark and if it is my PIR sensor would be turned on. If the PIR alarms arduino would control a relay, which would turn on a big halogen light.

This has dual purpose. To help myself see something on the yard when it is dark and possibly burglars will be scared and seen.

I don't have much idea where to get a good pecu switch or the relay to work with 220 V. Especially I would appreciate any hints which pecu switch would be good and cheap and would work with arduino?

Thanks for info,


Most PIR floodlights already have such functionality built in, would be much cheaper to use than an Arduino, safer than building your own, and a lot less work to install.

But that wouldn't be any fun, would it?

PECU stands for Photo Electric Control Unit, and they are typically just a Cds photocell in series with a relay coil.

Popular retailers such as Spark Fun sell Cds cells for a dollar or two. Using the one available from them, in series with a 4700 ohm resistor, would produce a nice voltage divider type sensor which could be connected to an analog input to measure the amount of light.

Spark Fun also sells a PIR sensor, which can pull a digital Input LOW when motion is detected, for $10.

They also sell relays which can handle 5 amps at 220 volts AC, good enough for a 1000 watt halogen light. Thats a pretty bright light!