I was wondering if it’s possible to use a raspberry pi based open-sprinkler to drive a 9v solenoid instead of a 24v. The reason why I’m asking is because my irrigation system is quite small and currently uses a gardena watering unit with a 9v solenoid in it. I don’t think I need a solenoid bigger than that and the fact that it runs off a standard 9v battery is quite convenient. What are the changes required to the pi extension board to make it work? Can the board be ordered to work with 9v solenoids off the shelf?
Your 9V valves are most likely based on latching solenoids, which means 1) they work only with DC power; 2) the circuit needs to be able to reverse the polarity of voltage applied to the valve in order to both open and close it. You can take a look at similar valves that I blogged about before: http://rayshobby.net/blog/?p=18 http://rayshobby.net/blog/?p=12
OpenSprinkler Pi cannot be easily modified to control these valves. Instead, I have an upcoming product OpenSprinkler Bee that’s designed to work with these valves: http://rayshobby.net/
(scroll down to check the picture of OpenSprinkler Bee, and you can also sign up to receive notification when it’s available).