[SOLVED] Sonoff DUAL Dry Contact

Hi there,

IO have modified on sonoff basic to have a dry contact for the thermostat following. Anyone knows how to modify the Sonoff DUAL to get dry contact as well?

I do not find any schematics to se where to break the circuit exactly.

Thanks, but no info there.

I have figured out where to break the circuit in order to isolate, and have a dry contact. I will try and let you know how is working.

hi, I have done that to control my two garage doors. I just unsoldered the output pins of both relais and bent the pins above the circuit, no cuting etc…

Ah, nice.

I guess is needed to separate a little bit the rele in order to have room to sold the cable, right?

This is what you mean?

right, it´s easier to completely remove both relais from the circuit board, attach cables to pin OUT1&2 and put the relay back in with only the remaining 2 pins soldered onto the circuit board…

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Hi, sorry to be reviving this old thread… but I’m trying to do the same thing right now - dry contact on the Sonoff Dual. It looks like you’ve figured a solution to doing this already, however I’m having trouble understanding how this was actually achieved. Are you able to please explain this to me in some more detail or post any pictures or videos? Thanks in advance!

Hey, sorry for the late reply. I did not see the email in my inbox.

I remove the soldering from the 2 pin of the relay, the one closer to the conections pin. Then you have to move up a little bit the relays and then solder 2 cables there (take care do not touch the board, I putted a cable tape in the board) and I connected the cables on the relay directly.

Before connecting anything, use a multimeter and make sure you have open circuit, closed circuit.

Some pictures:

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Thank you so much for this! I’m going to give it a try as well. I’ll report back on my progress. Cheers!

Am I correct in understanding that you have only one relay set up as dry contact in your picture?

yes you are right. I only needed one relay, but you can do the same on the second relay if you need it.

Hi thanks for the solution. I am about to do the same to control 2 garage doors. I’ve resoldered and set up the sonoff using tasmota. I have two separate door sensors that detect whether the doors are open.

Can you share your mqtt settings and rules? I keep getting warnings like this

2020-05-18 23:12:56.380 [INFO ] [st.core.internal.thing.ThingResource] - Received HTTP PUT request for update at ‘things/mqtt:topic:myMQTTBroker:sonoff_garage_door1’ for an unmanaged thing ‘mqtt:topic:myMQTTBroker:sonoff_garage_door1’.


I changed all my sonoff devices into Shelly. I cannot share anymore my mitt.



No solution, background info only. That looks like an update (“edit”) targetting a Thing, typically these come from a user of PaperUI.
It gets rejected “unmanaged” because the Thing in question was defined in a xxx.things file, and PaperUI edits are then not allowed.

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Yes i think that’s the problem. I was doing something in paperui and it did not like it!

Thanks… I managed to melt one of my relays taking it out :joy:now I have just a one relay system too

Hi Juan,

I am trying to understand your solution, but can’t figure out.
Where do you attach live and neutral?
Do you have more pics?

Tx, Pascal