Saturday, July 13, 2013
Gotta Know When to Fold 'em
For the past few months, I have burned up a lot of hobby time trying to build an interface to control the Orbit 58874 sprinkler control valve. These simply connect in-line with standard water hose connectors and cost about $20. However, they turned out to be quite complicated to control.
The valve connects with two wires. Sending a 24V pulse in one polarity will cause the valve to latch open. Sending it in the reserse polarity will cause it to latch closed. At least in theory. And, as a wise professor once told me: "In theory, practice and theory are the same. But in practice, they sure as hell aren't."
I had a 24V power supply, but it was a little too powerful. If you leave the valve powered for more than a second, you can burn out the solenoid coil. After melting one of my H-Bridge motor controllers, burning out several valves, and losing a couple of months, this project was officially no longer fun.
Fortunately, someone else has already gotten this working. If you are interested in this, check out http://rayshobby.net/ where you can find interfaces to these valves for Raspberry Pi and Arduino. I may just break down and buy his OpenSprinklerPi interface.
But now it's time to throw in the towel and move on to other projects.
UPDATE: I was mistaken about the OpenSprinklerPi. It will only support standard valves. That's easy - apply voltage and they turn on. Stop and they turn off.
So I have returned to this and will be building an entirely new interface board for the sprinklers. It will probably include an H-Bridge to control output polarity and relays for each sprinkler.