Can M1XIN handle 24Vac on a zone?

Ira

Active Member
I want my M1G to monitor (not necessarily control, at this time) my irrigation system valves. Can I simply tap into the two wires going to the valve and connect them to a M1XIN zone (the zone would be wired in parallel with the valve), or will the 24Vac on the zone damage the M1XIN? If it will damage it, is there any way to do this other than to wire a relay coil in parallel with the valve and connect the contact terminals to the M1XIN zone terminals? Sixteen relays will take up a lot of space in my can. Maybe some kind of optoisolator circuit? Maybe I can panel-mount sixteen relays on a small board.

Thanks,
Ira
 
you are not going to be pulling any power off the relay contacts, so in reality you can get the smallest relays you can find that operate off 24VAC coils.
 
you are not going to be pulling any power off the relay contacts, so in reality you can get the smallest relays you can find that operate off 24VAC coils.

Yeah. I found some small PCB-mounted ones that are about 1" x .5". Even with relays that small mounted to a PCB, by the time you throw in termnal strips, etc., it will be probably the size of the M1XIN board. I guess that's not too bad (if it has to be done that way).

Ira
 
From the specs on Elk' site:

Operating Power Range: 9 to 14 VDC

Isn't that the voltage used by the M1XIN when "powered up", as opposed to the voltage that can be applied by an external power source across a zone's terminals (if there can be any)?

Ira

I downloaded their manual on their site (login required) and couldn't find any more info other than that. I am not sure but doubt you could do AC as an input as I believe they are open collector (let's wait for someone to confirm this though). ;)
 
As I understand, the M1XIN applies roughly 14v dc power to the "hot" lead and measures the returning voltage. If it is still 14v it states zone contactor is closed, 7 volts zone contactor is closed with a resistor, 0 volts the zone contactor is open.

The sprinkler controller will apply 24v ac to the wires in order to power a solonoid in the valve. I don't know what the M1xIN will do if it sees 24 vac, but I doubt it will be happy with that. Even if it doesn't fry it, it won't be able to read it since it is designed to read dc. You will be pumpin 24vac current into the power source on the Elk that is itself making 14 vdc.

I think your solution is to go ahead and buy a bank of relays as mentioned. Trouble is, I don't think relays that trigger on 24 vac are going to be easy to find. At least not ones that aren't designed to have huge loads on the contacts and cost a lot (times 16). Most low load, inexpensive relays run on 5 or 12 vdc coil. You could put resistors on the lead to the relay and drop to 12 or 5 vac, then add a diode to rectify it, but that is a lot of trouble. Might just buy 2 Elk relay boards and let the Elk run your sprinklers like I do. I also have 16 zones.
 
I found these PCB-mount relays. 24Vac, about $4 each, fairly small. They seem a little power hungry though at 5 watts. But since I should never have more than two or three zones running at a time, it shouldn't be a problem.

Functional Devices offers a few track-mounted relays that have 24Vac coils. They are about twice the price, and would take up twice the room in the can, but it would be a lot easier to set up and maintain.

Am I figuring this correctly? The Magnecraft relay coil pulls five watts, which is about 200mA at 24Vac...right? The FD relay spec sheets say the coils only pull 31mA at 24Vac. That's about 1/7th the power usage for the FD relay.

I will probably end up having the sprinklers capable of being controlled (instead of just monitored) by the M1G at some point so I can use CQC to do some simple things with the system. But first, I'm adding a Rain8netPro controller (aleady sitting on the shelf) and McsSprinklers as my primary controller. I'm also wiring it so that I can flip a switch to bypass the Rain8/McsSprinklers and use my existing Hunter Pro-C controller. I'm going for maximum overkill, maximum redundancy on this project.

Thanks,
Ira
 
That is pretty cheap for the relays. I don't envy you, though, doing all that work to mount them all nice and organized on a pcb. They have 16 relays all premounted on pcbs for sale on ebay, but they are all 5/12 vdc coils.

5 watts seems like a lot for a silly little coil. It might just be worth confirming that the 24vac power source on your spinkler controller doesn't get pushed to/over the limit by that. I really don't know how much juice they build into those things or how much a typical sprinkler solonoid takes which you would need to add to the 5w.

If you decide instead to just turn things over to Elk, I would be happy to export my sprinkler control rules to you saving you much of the rule writing labor. I have set it up with several additional features that make it easier to use.
 
That is pretty cheap for the relays. I don't envy you, though, doing all that work to mount them all nice and organized on a pcb. They have 16 relays all premounted on pcbs for sale on ebay, but they are all 5/12 vdc coils.

5 watts seems like a lot for a silly little coil. It might just be worth confirming that the 24vac power source on your spinkler controller doesn't get pushed to/over the limit by that. I really don't know how much juice they build into those things or how much a typical sprinkler solonoid takes which you would need to add to the 5w.

If you decide instead to just turn things over to Elk, I would be happy to export my sprinkler control rules to you saving you much of the rule writing labor. I have set it up with several additional features that make it easier to use.

The wall wart that came with the Rain8 is 20VA. The one with the Pro-C is 40VA. I'm replacing both with one that is 100VA. The valves spec's show 370mA inrush and 190mA holding current. The spec sheets don't show how much power the controllers use (i.e., not including the power to open a valve).

I saw your Elk irrigation rules on the other thread. You have some good ideas/functions that I had not considered. My plan is to use the Rain8netPro and McsSprinklers as the primary means of controlling the system. The goal is to have the Pro-C provide "backup" capabilities (might as will keep it in the system since it's already there) and to do various "special" things with the M1G/CQC that aren't easy to do with either the Rain8/McsSprinklers or the Pro-C. I'm also thinking that by monitoring the zone valves with the M1G, I could also use the M1G, a few simple rules, and a M1G relay controlling the main power to the other two controllers as an additional failsafe layer to shut down the system when something isn't right, i.e., a zone valve or the master valve has been open too long. A couple of days ago, something caused the Pro-C programs to get scrambled and most of the zones were scheduled to run for six hours instead of the normal 30 to 90 minutes. The M1G could have sensed the first long running zone (at runtime) and shut off power to the system.

Ira
 
The main sprinkler screw up problem that I have had to deal with is stuck valves. Sadly, none of this stuff we are talking about will detect that. A flow sensor on the sprinkler line that feeds info to the Elk or some other automation system to warn you when flow is occuring when flow shouldn't be (or vice/versa) is something I would have interest in.

Has anyone ever done something like that?
 
I have a master valve near the pump that is opened whenever any zone valve is open, so for me to actually notice a valve that is stuck open, there would need to be a stuck open zone valve along with the master valve being stuck open. The master valve is in my pump house out of the weather, so it probably has less of a tendency to stick. What I should do is periodically open just the master valve to see if there are any zone valves stuck open. I do run thru each of the zones periodically to make sure none of the valves are stuck close or I have any damaged sprinkler heads.

You are right though. It could all be monitored easily by installing a flowswitch or flowmeter (connected to the M1G) on the main line before any valves to detect actual flow (or lack of) at various zone states. I have a dry contact that closes whenever my well pump turns on, so I could deduce some things based on valve status and pump status. It's a little less exact because the well pump also provides water to my home, and I don't currently have a way to detect actual water flow to either branch. I'm working on detecting flow to my home based on the flowmeter in my water softener, but that's a different subject (still a work in progress).

Ira
 
Ira,

I was just thinking about you putting that pcb together and thought, it might be easier to buy one of those $50 16 relay boards on ebay and put a diode and resister in to allow operation on 24vac. The relay coils usually allow for a somewhat broad input voltage. It should work out that if you put a resistor in series with the relay that has equal resistance to the coil, the volts should be halved at each item. I am not positive about the diode and you might see if someone with more EE background can chirp in, but it would result in a pulsed dc voltage. Question is if that is going to pull and hold the relay coil like normal or if it would "chatter" instead.
 
The main sprinkler screw up problem that I have had to deal with is stuck valves. Sadly, none of this stuff we are talking about will detect that. A flow sensor on the sprinkler line that feeds info to the Elk or some other automation system to warn you when flow is occuring when flow shouldn't be (or vice/versa) is something I would have interest in.

Has anyone ever done something like that?
Pobbisly use a leaf sensor from Hobby Boards to detect 'when' the sprinkler head is on. There are a few posts here about interfacing them to a variety of hardware controls.
 
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