Update: I've updated the design of the board and the transistors used to ensure better compatability with the Orbit valves. I was getting reports from folks that some valves would open but not close with the shield. The updated design can be downloaded at the bottom of this post.
I've been working on a rather large project for some time now and while my new h20 shield is just one piece of the larger project, I thought it deserved it's own post and documentation. I can see this shield being quite useful for lots of folks wishing to control water using one of the fairly inexpensive Orbit 62035 garden hose valves.
First, allow me to give credit where credit is due, the hard work for the control circuit and voltage booster came from this incredibly smart gentlemen and the shield wouldn't be possible without his hard work figuring out how to control the valves! His design for controlling the valves works wonderfully!
This shield is a three valve controller with LED indicators for valve status. I used the long headers thinking I'd make the shield stack-able but the 50v cap scrapped that idea. If I make another version, I'll use a different cap/layout to ensure you can stack this shield, as it now, this will just be the top shield in my project. I also used only through-hole parts (I normally would have used nearly all SMT components) to make the shield easier for folks to solder and I had many of the components in through-hole package on hand.
The circuit is quite simple really, it's comprised of two main parts, the 24V voltage boost circuit which is required to open and close the Orbit water valves and three open/close control circuits. The shield uses 7 digital pins and 3 analog pins. I have one pin each for open and close for each of the three valves, they each drive a transistor which close the 24V through one of the two valve connections. One will open the valve and the other will close it. The final digital pin is used to control the LT1303, when held high, the circuit will shut down thus saving power as the 24V is only needed when opening and closing a valve. I've used the three analog pins to control the LED indicators for the three valves, I needed the other digital pins for other shields that are part of the bigger project I mentioned earlier.
I've included high-resolution pictures of the completed board along with the Eagle schematic and board files and a sample Arduino sketch for those interested! As you can see from the video below, the board works perfectly! If you find a use for this design, let me know, I'm always fascinated by how folks use controllers like this!