Control the flow of fluid using the flow of electrons! This liquid valve would make a great addition to your robotic gardening project. There are two 1/2" (Nominal non-taped National Pipe) outlets. Normally, the valve is closed. When 12VDC is applied to the two terminals, the valve opens and water can push through. The valve has a gasket arrangement inside, so there is a minimum pressure requirement of 0.02 Mpa (3 PSI). Also, liquid can only flow one direction.
We tried this solenoid at various DC voltages and found we could actuate it down at 6VDC (although it was a little slower to open). Here is the current draw table for various voltages. We suggest a TIP120 or N-Channel power FET with a 1N4001 kickback diode to drive this from a microcontroller pin. For a power supply, our 9V 1A or 12V 1A power adapters will do the job.
If you want a beefier water valve, we also carry a brass version which does not have a minimum pressure requirement and can be used with liquid flow in either direction.