[Paul]

@Ray; sorry I didn’t respond sooner. I checked back a couple times and didn’t see your post, and I had the “Notify me of follow-up…” checked but never got notification. In any case… yes, despite the fact that I said “SCRs” I meant a shift register and triacs/relays/SSRs. If I can drive a shift register at the end of a 50′ wire run, it should do what I need. I want to keep it small because I don’t ever anticipate putting even 8 valves in a box with the current layout of my irrigation system, but I’ve got a place where there used to be one valve and I’ve grown it to 3.

I thought I posted another message to this thread, but it’s not here so maybe I got sidetracked and didn’t press “send”. (DOH!) One solution I found since the original post would be to convert the signal I’m sending down the wire to DC, send one polarity down for one valve and the opposite for another valve, and have diodes in series with the valves to get them to respond to the proper voltage. This could be done with a 24VAC relay that would be driven by the OSPi and a rectifier circuit to convert the 24VAC to probably about 12VDC (I’m not sure about the AC-DC voltage conversion to drive the valves). This wouldn’t allow much expansion, but it should work to add a single valve.

Maybe I’ll throw together a mini version of the expansion board, give it a try, and post my results here… as time permits. If it works okay I’ve got a couple more valve boxes that could use an extra valve to add a zone, but none of them would have more than 4 valves so a full expansion board wouldn’t be practical.

[Paul]

I’m bumping this old post up because I have a similar need. There may be other threads that cover the concept, so please direct me if you  know of any. I’m not coming up with the right search terms for a better hit. Has anyone come up with a method for controlling more valves that they have wires to drive directly in the valve box? I ditched my old sprinkler controller because it’s limited to 6 zones and I’ve added a couple more, but I also don’t have enough strands of wire in the valve boxes to support the additional zones. I could run the wire, but I’m hoping for a “cleaner” solution. I’m kicking around a couple of ideas for adding zones, but my electronic design knowledge is weak enough that I’m not sure of the feasibility.

One idea would be to put a small board with a serial to parallel shift register, voltage regulator, and SCRs in the box, and send the power, clock, and serial signals down the existing wiring. I don’t know how feasible this is. Would the attenuation in the sprinkler wire be too high to get a clean clock signal? I don’t know how sensitive shift registers are, or whether there’s a common strategy for cleaning up the clock signal at the remote end of a long run. I’m sure there are other problems with this plan that I’m not anticipating.

How about a wireless remote controller, such as an Arduino Yun? Or possibly a wired Attiny board that can process a serial signal and break it out to drive the valves with mosfets or SCRs? I’ve got some DigiSpark Digistump boards I bought on a kickstarter I could conceivably use. Have any of you solved a similar problem or know of a non-OSPi project that I could leverage or learn from?
Thanks in advance,

Paul

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