After you get your timer built, it's time to hook up your system. Start off with a 24 hour timer. This is the type that you would use to turn lights on and off, when you're not at home. They are cheap and readily available. This is set to turn the system on at daylight and off at dusk. The short interval timer, the one you built, plugs into this. Next, in line, comes a 24 volt transformer, available at plumbing or electrical supplies. This is used, because the solenoid valves are 24 volt. Hook the input side of the transformer up to your short interval timer. The output side gets hooked up to a plastic solenoid valve, the type used for underground sprinkler systems. (Shop around for this. Plastic ones are usually available at home improvement stores for $10.00 -$20.00. Metal ones can cost $80.00 or more.)
The in side of the solenoid valve gets hooked to a water supply, and the out side goes to your mister nozzles. These are plastic or metal and are available from greenhouse supply houses, relatively cheaply.
When setting up your nozzles, lay a piece of PVC pipe down the middle of your mist bed. Put the nozzles at the top of risers attached to this pipe. By doing it this way, any excess water in the pipe, when the solenoid shuts off, will run down the riser and not drip on the cuttings. If you put the nozzles in a pipe, suspended over the bed, when the solenoid shuts off, water will drip from the low point, causing rot.
After hooking everything up, plug the 24 hour timer into an outlet, open the water supply to the solenoid, and you're in business!