Need another Relay wire

[apostolakisl]

When I put my well in, I ran a low voltage wire to it for any future valves that I might want to control at the well (originally there were no valves at the well). So, I have installed a valve and guess what, I now need a second one down there. Trouble is, I only ran a single pair (hot/common).

Being the guy who always talks about using conduit, I am dissapointed that I didn't follow my own advice and run plenty of it (I did run a conduit but I have it filled with high voltage stuff).

Are there any tricks where I could use that single pair to control two valves or am I just going to have to trench another wire? I did at least run a conduit from the attic out the wall of the house on that side so once I get a wire to the side of the house I can easily get it into the attic.

 

[JimS]

There are a several possibilities...

Do you need independent control of both valves or will only one be on at a time. If only on is on at a time an easy way is to use DC relays and diodes so one is on with positive voltage and one on with negative voltage.

If you want independent control you could use something similar but excite the line with AC voltage. Use the positive half cycles for controlling one relay and negative half cycles for the other. Rectify and filter at the well end and use DC relays.

Or use the neutral of the power wires as the return and you have one low voltage wire for each relay. I would think this would be acceptable as far as code is concerned but I could be wrong. And you may not have a neutral at the pump if it is 220V.

If you really want to get carried away you could send pulses down the wire and decode them at the other end for as many devices as you want. Don't know of any off the shelf hardware for this but it would be easy to do with microprocessors.

 

[apostolakisl]

I can't use the neutral as a hot becuase it ties into all the other zones running around the yard. But the rectifier idea is a possibility. That is the kind of thinking I was looking for. Thanks.

 

[JonW]

You could use an RS-485 based relay board. It's serial connection only requires 2 wires. You could then send serial commands to trigger your relays.

 

[tmbrown97]

What about converting the existing 2-wires to a 1-wire network? It looks like there's a good number of options for doing addressable relays via one-wire that'd give you way more than 2, and the ability to add other sensors if you should want.

 

[apostolakisl]

I had thought of rs485 but wasn't sure if there would be an issue since the neutral is shared with all of the sprinkler valves around the yard.

Since I have an Elk M1G I was considering an Elk M1RB. I just don't know if it would degrade the signal piggy backing onto the sprinkler wires.