Use in parallel with other controller

[chicagojim]

Is it possible to utilize another controller in the system with all output control lines connected to both the Open Sprinkler and the other controller except for the common. I could switch the common between the other controller and the Open Sprinkler with a SPDT switch. Thus I could put the switch in the “old fashion controller position” for my not so web savvy spouse 🙁 and switch it to the Open Sprinkler for myself. We would use the other old controller in a local manual mode only which is very easy and while we are away, I can flip the switch and control everything remotely and even check how the lawn is doing by logging into my webcam. I could remove power from the other controller if necessary by adding one lead of the 24VAC to a DPDT switch thus removing power from the other controller completely if necessary but don’t think that would be required if the transformer is rated to power both units simultaneously. I can see no reason why this shouldn’t work and I can mount the Open Sprinkler along side the old one in the same enclosure.

[Ray]

This has been brought up more than once in the past. I suggest doing so only if you have a good idea how the other controller works internally. The reason is that not all controllers work in the same way. On OpenSprinkler, one wire of 24VAC is tied to the circuit ground, and the other wire is common. For each solenoid, one wire is tied to common, and the other is tied to a triac. Switching the solenoid is done by turning on the triac thus completing the circuit. On other controllers, the circuit ground may be the common wire; also many controllers use an isolated design. Without knowing the underpinnings, it’s difficult to tell whether a SPDT to switch between the common wire is sufficient to get them running safely in parallel.

[chicagojim]

Thanks for the reply. I will check out my other controller and will decide how to proceed. I am thinking a 3 pole double throw switch on the AC input line and also breaking the common may be a better solution . Than way the the off system will be completely floating if there are no earth grounds attached to either PCB. Right now there are no earth ground connections. BTW I have the unit on order (not here yet) and will advise what connections are made to my current Irritrol Rain Dial-R controller. I am an EE and will reverse engineer the schematic of the Irritrol before making any common connections so that nothing bad happens. There are MOV’s on the Irritrol PCB which would also help protect the Open Sprinkler.

[chicagojim]

I just confirmed that Irritrol does have one side of the 24VAC tied to common as you indicated that OpenSprinkler has. Thus a DPDT switch switching the 24VAC line connected to the commons and switching the common line to the solenoids should be all that is required. There will be a AC signal on the active station triac of the unit that is not powered up but that AC signal will have nothing to reference to since the common line will be floating. While I will get everything ready, the Chicago weather will not permit an active test as I have no spare solenoids sitting around in the basement. I will advise of how this configuration works as soon as testing is possible. I will only keep this configuration until a local manual control becomes available on the OpenSprinker. 😀

[Author]

Posts