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A WiFi sonoff with dry contacts

Many people would need the wonderful sonoff wifi switch to simply close two contacts. I mean the device should be powered by main but the contacs of the relais shouldn't be connected to main but simply connected to the output connectors.

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I solved using the Sonoff 4CH Pro R2. It’s only a pity that I had to use a 4 channel module only for one contact...

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This is where the money is. A standard US single family home has a central air-condition system controlled by 24 VAC. All thermostat sold are mostly 24 VAC. All sprinkler sold are also controlled by 24 VAC. Yes, you can now cut off the PCB to expose the relay contacts for the 24 VAC. But the AC supply route are thick and are on both sides of the PCB.

The closest we have now is the Sonoff SV, for safe voltage. Use a spare USB phone charger for 5V input and 5V output. Get one SV for each sprinkler valve. Then you get a bank of 5V mechanical relays from itead. A 6 zone irrigation contoller cost you some $30 with virtually unlimited of programs. Not worth my time to cut or solder. And since these controllers are mostly hidden in the garage, nobody will complain the size of the smart junk.

Many smart controllers cost several hundreds!

What we need is an SV version with the "dry" relay contacts exposed to the outside world so the 24 VAC can be connected directly. Without schematics, I don't know if the current version is capable of this.

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I miss that option too. Workarround is to remove few mm of the neutral and live line on the pcb between relay and power supply.

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Can you explain how you used it as a dry switch please?

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Exposing relais NC contacts


I am really interested in some of these objects and I need (really) many of them for my projects but I need a layout that exposes the NC contacts of the relay, not just the NO ones!!

That is a vital requirement for application where you want the electricity go through two different paths with the FISICAL certainty that they are not enabled at the same time (software can't do so).

The simplest application of this is using a sonoff relay as three-way switch together with an in-wall three-way switch.

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Here is a good description of how to achieve that

Hi, Do you sell Sonoff Basic with dry output contacts?

so does anyone know how to modified the Sonoff SV low voltage systems or even a high voltage system to have the output work as dry connection just to open and close a loop?

could be low or high voltage input to power up system just need the system to have a open and close a circuit.

im a heating guy  specializing in pellet stoves and gas fireplaces. 

I would love to find a dry contact system just to open and close a millivolt loop used on thermostat circuits of gas fireplaces, pellet stoves and other millivolt systems. I have come across one customer that used some kind of unit like this to run in line with a wall thermostat. He was able to turn on the unit from his phone as long as the thermostat was set to a desired temp. This way he could prevent the unit from coming on when gone. 

I could also make customizable cell phone activated remotes for gas and pellet stoves.

Luca, I just asked for something similar right now. I supposed that with the 4ch pro it could be done. You just confirmed it. The logical thing would be that the "1 Channel Inching / Self-Locking WiFi Wireless Switch 5V 12V" module also allows that type of contact. In my case it is for: cables together = alarm connected / cables separated = alarm disconnected.



 Hi, I would recommend that sonoff should make an ac version of 1 Channel Inching /self-locking WiFi Wireless Switch 5V 12V,  the sonoff pro 4ch is to much for some project (size and money).

There is other alternative until a sonoff is available shelly 1.

I did it too but playing with Mains is not so safe.
l wonder if you could just tap the 2 input contacts of the coil of the existing relay off and out of the case to drive another (probably 3 volt) relay with dry contacts to control whatever voltage you needed to control?? You'd still have the mains relay if you needed it and the soldering would be easier. My only concern is whether the sonoff board could drive both relays without cooking itself but you could always add a switch to use only one at a time. Anyone done this or have a 3v relay sitting around?
I found this online Do you sell this model direct? And is the output headers dry contact/no power of using the 5volt USB to power switch like the SV 5v switch? If so I think this unit is something I need
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