Convert Sonoff To Switch 27vac Solenoid

Can you use a sonoff basic that’s modified to low voltage, to switch a sprinkler 27vac solenoid, or is this only limited to 5v devices?

I guess it depends on how it has been modified.

It’s the typical mod that enables it to be used as a garage door opener even though it’s plugged into mains. Here it is, you can jump to 3.50 mark on this UT vid.

Wait… if i understand correctly: you modified your sonoff like a man on video, so you’ve got dry contacts on output relay, right? If so, you can switch anything with this relay, voltage is not important, only limit is current, i think it’s 10A max.
If you mean power supply for basic: if you didn’t mess with it then you must still connect sonoff to 230V if you want it to work. So, connect primary connector to 230V and then you can use output connector for 27VAC solenoid.

Yes to modify like the video. Yes it has to be connected to mains. No I won’t mess with that part.
My fear was since sonoff is now converted to low voltage on output side, by wiring 27vac was that gonna travel to other components and burn/destroy them since i would imagine those operate on 5v. But if the 27vac is just hitting the output relay to be switched, then my concern is unfounded. This is what you are saying, right?
All the same it’s a $5 sonoff, I will do this of that’s the sacrifice to establish the theory.

Garage door.
I replaced my garage door opener with the new Wi-Fi connecting types. I connected a sonoff sv to it but it wouldn’t open. I was told my new GDO has a dry contact. Does that mean this modified sonoff should work since it’s dry contact output now?

Ammm… wrong. :wink: it’s not converted to “low voltage”, but it’s converted to OPEN CONTACTS, that means NO voltage, contacts are “in the air”. So it doesn’t matter what you put on them, as long voltage is not too high (say 1kV). say, you can still switch 230V lamp with those contacts. OR open garage doors. Or…you name it…

If garage doors have dry contact it should work, yes, since this means that you only need short two wires. Try it out: short those two contacts on garage door electronics and door should open.
Do you have a pushbutton in your garage? If so, connect new sonoff parallel to it.

Yes push button. In my old garage door shorting the twow wires worked, so a sonoff sv worked ok. That same push button did not work for the new opener since i didn’t want to replace everything but just the opener and drive chain. So I had to wire the new push button for the new GDO. For the new one shorting the 2 wires does not open the door. I was told it’s something to do with wet vs dry contacts or switch. Does that make sense? As you can tell I have very rudimentary knowledge of electronics etc, but I can diy my way through stuff with instructions.
I will be executing this mod and test it later today when I get home.
I should mention mains are home use 110v not crazy levels.

Success switching 27vac power supply for the sprinkler solenoid.

No joy on garage door opener. Not working. I connected the sonoff outputs into the gdo push button wire receptacle. Does this have to do with dry or wet contacts?

If you don’'t have dry contacts you will be putting 110V on your garage door opener ELV circuit which will destroy it.

Assuming you do have dry contacts you need a momentary action. “Push-release”. Not permanently on/off.

I tested the output and continuity on the unit. There’s no 120v output. The mod was successful.
I changed inching setting to half a sec. but no joy. I will retest this but if anyone has an idea I would appreciate

Then try to give the door a short off-on-off pulse rather than just switching it on.

I did, set sonoff to inching mode, duration 0.5 secs. I shorted the wires and the door still didn’t operate.

Anyway I was told this looks like the best explanation why it did not work.

“The new liftmaster/ chamberlian/ craftsman opener push button connections are encoded and you can’t hook up foreign push buttons. Try just touching the two bare wires together, if your door doesn’t respond, the system your trying to add will not work.”
I think this ensures they hog their customers’ options if you buy their GDO. The unit is the chamberlain D2101C. I wanted an option to add a tasmotized sonoff to ensure local control as sometimes I have had a few occasions when their myq app could not reach chamberlain network. The one clicker is in another car.

This moded Sonoff will operate a foundation watering line hooked up to a spigot, twice a week for a couple of minutes due to crazy shifting Texas soil. The install location is remote, no internet connection there. I will program sonoff before taking over there for install, and it will run with the saved times. Question is on the eWilink app is it possible to run this schedule from say April to October? I can’t seem to figure out an option for this.

There’s always a way…
I didn’t find any “decent” manual, where electronics would be explained, but it seems that only connector you have is for safety gear (photocells…). So, if i see correct from user manual now you have only wireless pushbutton (=remote control) for opening garage, right? Open this remote control and solder two wires parallel to existing button. Connect those two wires to sonoff’s relay output. Done…
Only thing is: you must have one spare remote control only for this purpose…

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Of course! Thank you! I remember seeing this idea a while back on UT, bored pro’ly rolling on 420s, so I never followed up on it.

I will add a wyze cam facing the door but what can be integrated into this sonoff setup to know the garage door is up or closed? I do have some reed switches, and a sonoff RF bridge … any suggestions? Alternatively I don’t mind buying another brand of what would be needed.

The remote switch has 4 legs ???, GD opens when they are diagonally shorted. Is soldering on either aok or you guys with electronics knowledge please confirm or advise.


Remot button switch has indeed 4 legs, but two and two are connected. Usually you must connect the ones on shorter side (or diagonally also works, yes).
I have a reed switch mounted on “door closed” position. Sonoff basic has enough pins to make one (or two) an input. Then you connect that reed switch to sonoff and you’ll have position monitoring. You can find sonoff’s pinout (where are GPIO’s) on the internet. Here’s one of the links:
Edit: you can use rx and tx pins, too, just disable logger in esphome. One of inputs can be existing button if you don’t need it for relay switching, (just make sure it’s not tied to GND when module boots), etc…

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Next I want to install a hidden momentary switch in two cars to trigger the GD to open. GDO remote is wired to the moded sonoff RF, positioned inside the garage. This setup works great as two people can now open GD using eWilink app. I can simply buy two 433mh car key remotes but where’s the fun in that plus adds to car keys being more bulky. The sonoff is the RF type.
I also do have those tiny 433mhz relays with a car type remote. I know there must be a way to make this work. Any ideas?

You mean like chinese set: receiver board with one or two remotes? Just connect receiver’s relay output in parallel with sonoff (garage remote button) and these chinese remotes will also open garage doors.
Of course, you will need some kind of power supply for receiver board…

Soldered the points marked red (in pic above above), set ewilink to inching mode for half a sec., but the unit doesn’t work. Sonoff is responding to ewilink app-I can hear the relay click, at on, then click again when it goes off after half a sec.
Even the GDO remote itself is not working, nor is the LED light turning on, it’s just quiet. Battery test is aok, it has 2.4v.

Any suggestions?

First, Tested sonoff mod with 24vac sprinkler valve, worked great. Sprinkler turns on and off.

On the GDO itself the soldered bottom part has continuity just fine. Before soldering, touching these two leads would pop GD open. Now it doesn’t. On the top side, testing continuity on the same leads meter reacts only button is pressed.

Tested soldered wires bet. sonoff screws and board, both wires have continuity.

On sonoff’s output screws point,
There’s no voltage output on sonoff, while it’s plugged into mains. But there is 2.53v when battery is inserted in GD remote. And there is continuity with and without battery inserted, even operating sonoff manual button, there is continuity, with or without battery inserted.