NO Voltage Dry Contact Relay


Looking for a Z-WAVE relay, either 110V or 12V or less INPUT.
Catch is it must put out ZERO, a big fat naught, voltage when it closes the relay.
In other words, I just need something that will close a circuit.
If I use it as a timed momentary switch, even better.

So the why…

I have a bee in my bonnet - I need to integrate my alarm system with ST. Just believe me when I say it cannot be done. I have however thought of a round-about, almost back-doorish way of doing it… I have tried my proof of concept and it works!!!

I opened up one of my remote alarm fobs, and hardwired the on / off micro-buttons using a simple piece of electrical cable. When I close the loop for approx. 2s the alarm either activates or deactivates depending on the circuit I closed.

I suspect I will fry the fob if any form of voltage is applied (the fob has its own micros cell of course for power). So, I need a power high/low input voltage relay that can dry close a contact…

The closest I could find is a MIMOlite, but I get the impression it too provides current on the OUT side.

Any other thoughts? Remember, champagne thoughts on a beer budget! Tagging our resident expert, @JDRoberts

Thanks in advance

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A Fibaro relay should do it.

Can be used in a similar manner to this:

Is that what you’re after?

I did something similar with an Orvibo unit as shown here:

Does this device no put out a voltage as well? I’m totally ignorant on this, but my understanding is that the OUT side of the relay switches all put out some form a voltage as well…, to trigger, as per the garage door opener example, the garage door. Or am I waaaaay off target?

Even the Fibaro says:
Power output (resistive load):
2500W for 240V AC
1250W for 120V AC

Again, I may be way of target…


I don’t have one but this confirms they are dry:

Fibaro 1x2.5Kw Relay Switch
Single relay switch contacts
Maximum load: 10A
Dry contacts for switching alternative voltages
Dimensions (LxWxH): 42 x 37 x 20mm

Fibaro 2x1.5Kw Relay Switch
Dual relay switch contacts - independent control
Maximum load per channel: 6.5A (1.5Kw)
Maximum total load: 10A
Dry contacts for switching alternative voltages
Dimensions (LxWxH): 42 x 37 x 20mm

The Orvibo is definitely dry, you set a dip switch which selects either dry, low or high.

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The MIMOlite will work. The NO and NC contact points on the MIMOlite are absolutely dry contacts. You would need MIMOlites (one for arm, and one for disarm). You can modify the MIMOlite device type to operate as a momentary relay (with adjustable timing). This is how I integrate my doorbell. More info here:

The Linear (GoControl) Isolated Relay is another one that will work for you:

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As others have said, “can” output and “always outputs” are two completely different things. :sunglasses:

Check with the device manufacturer if you’re unsure on an individual model, but there are a number of these that have dry contacts.

Sooooooooo, the light finally went on, “dry contact” means no voltage?

Dry contact may mean any of the following in electronics: No current: A dry contact is the synonym of volt free - it is not “wetted” by a voltage source. Dry contact can refer to a secondary set of contacts of a relay circuit which does not make or break the primary current being controlled by the relay.
Dry contact - Wikipedia, the free encyclopedia

If so, I’m on my merry little way… Now to warm up my soldering iron, get out the 1000x magnifying glass, and ruin a perfectly functional fob. But if it works, when I enter AWAY mode, alarm on! And HOMe = alarm off. Perfect Frankenstein marriage of my alarm & ST; what ST should have been to start with!.

Thanks to all - much appreciated.

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The biggest hurdle you will encounter is the 2 seconds press with the fob. I don’t know how you are going to implement it but I use an Aeon z-wave plug, a usb charger and a 5vdc relay to control my car remote starter fob with a custom device handler for controlling the timing. You wouldn’t want to hold the fob button too long other the battery won’t last and ST is not very good with timing unless it’s built in the device handler.

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Have a look at the device handler above that I modified for the orvibo. Instead of on/off it carries out a momentary press by pausing in the code. Might help.

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@Navat604 & @brumster - Thanks for the thoughts… Before I can even start looking at code I need to order a relay!

Mmmm, I have a Linear FS20Z-1 currently in use for my garage door; maybe I should re-appropriate it for my project.

@Navat604, I have no problem in powering the fob permanently with a separate charger as well, assuming I can get an output matching the battery in the fob. Would you mind sharing custom device handler used for timing control?


This device handler is only for Aeon z-wave micro and plug so I don’t think it will work with other brand. Here is the post on it and it’s at the very bottom.

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Look at the link I posted for the MIMOLite doorbell. Use that as a template. You can modify the code for whatever device handler you use to make it momentary in the same way.

If coding ain’t your thing, let us know and someone here can modify a DH for you

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I know this is old but so people know as long as you have 12v and a relay. You can use the 12v to activate the relay. Then use either side of the relay and bam zero voltage with a 2 dollar relay…