An OpenSprinkler user, Maxwell, sent me this photo to share. Here is the description:
Thought you might enjoy what I’ve done. I am using 2 expansion modules. There are a total of 17 zones with 3 futures for the sprinklers. Then I added 4 24vac relays. As of now I have 1 relay for an outlet on my fence that will power LED Christmas lights. Waiting for inspiration for the other relays.
Also, note that all current versions of OpenSprinkler have a built-in relay (5V coil voltage, contact rating 120V / 2A and more recent version 240V / 3A). I would be cautious to use them to actually switch power-line devices, because the PCB traces are probably not thick enough to run a high amount of current at 110V. But they can perfectly switch low voltage (like 40V or below) devices.
I modified OS for a friend of mine, who want to use it also for christmas lights. To use an easy to find 12VDC power supply and 12VDC relais on outputs for it, I changed the 8 triacs on output in 8 npn transistors and resistors R1 to R8 in 10kohms. It works fine.
To note the polarity of power supply, I marked the connectors red and blue.