[GrowColt] shows you how to modify a lamp timer for use with hydroponics. You can pick up this type of mechanical timer at most local big box stores for around $5. The timer plugs into an outlet, and the device you want to operate plugs into it. [GrowColt's] end goal is to make the timer repeat every 35 minutes, routing power to the connected device for about 50 seconds each cycle. It will operate the pumps and misters in his hydroponic garden to keep the plants hydrated and keep the nutrients flowing.
We’ve embedded his detailed process after the break. It’s not all that difficult, requiring a few common hand tools, some glue, and rubber washer. There’s a gear box inside which controls the timer. Reorganizing that gearing makes it repeat more frequently.
Not into hydroponics, but looking for watering help with your greenhouse? Check out this system which monitors water sensors and dispenses H2O accordingly.