A quick update of on-going development: I have been working on an experimental version of DC-powered OpenSprinkler. It’s powered by 9V DC power supply which is easier to source world-wide. Although this is 9VDC powered, it’s still meant for 24 VAC sprinkler valves. Technically this is based on my research of 24 VAC sprinkler valves in this blog post (http://rayshobby.net/understanding-24vac-sprinkler-valves/). Long story short, the controller uses a boost converter to bump 9VDC up to 24VAC in order to energize the valves initially, then drops the voltage down to 9VDC to supply the required current by the sprinkler valves. We’ve done some initial tests and it seems to work well. Some advantages of DC powered OpenSprinkler include: 1) power supply is lighter and easier to source; 2) the same controller can work with both 24VAC valves and DC valves (like 12VDC or 24VDC valves); 3) a DC circuit also makes it easy to do current sensing and detect shorted solenoids.
We will be releasing an experimental batch of the DC controller soon, hopefully within a week or two.