Introduction: Control Heater Switch With Relay Using Sonoff Th10

sonoff devices allow you to power on and of electric equipment. the model th10 specifically is projected to switch heaters on and off with temperature control and time schedule capabilities.

the problem comes when your home heater is powered by gas and you have a wall switch to send an on and off signal to the heater itself.

in this scenario the heater is always powered and the switch only closes a circuit to tell the heater to start heating.

sonoff devices only have power output. from the output you can only get 110/220v. feeding the main voltage to the heater board the only effect you can obtain is an explosion.

but you can modify the sonoff device to open and close a relay for you without pushing the main voltage on the output. basically you can transform a sonoff th10 into a remote controller relay.

it only takes half an hour to do the job.

Step 1: What Do You Need

you need four pieces of small short wire and a female connector. it can be pin jack, a 3.5 jack, mono or stereo or any small female panel installable connector. I used a 3.5 stereo jack i had hanging around in the desk.

then a cross screw driver, soldering tools and a good desk light.

Step 2: Open the Th10 and Check Layout

this is the device, opened on my desk. the relay with the white label on top should be removed.

the output of the relay cuts the 220v main circuit so you don't only need to remove it from the rail but also to phisically move it from the high tension side of the board, to avoid incidents.

Step 3: Relay Removed

this is the board without the relay.

Step 4:

now you have to solder two wires to the relay control pins, as shown in Pic 1, the pins on the left in the picture.

pins on the right side should be left empty.

then you will glue the relay upside down on the safe side of the board, the 5v cc side! that's mandatory.

you can now solder the two previously soldered wires to the control pins of the relay. remember, the control pins are the two aligned ones.

the two misaligned pins will be our output in the next step.

Step 5: Hole for Our Female Connector

whichever connector you decided to use, now is the moment when you have to make THE HOLE.

you need a hole for the connector, next to the original hole in the case. the original one hosts the temperature sensor connector that comes with the device. temperature sensor is external, can be changed and can be ordered from a list of different types.

next to that hole and a little bit higher you will make a new hole to host your new connector. I used a small drill.

remember to keep the case panel far from the board when you make the hole.

Step 6: Install the New Connector

you can now solder two pins of your new connector to the to misaligned pins of the relay.

then you can screw down, glue or lock the connector in the new hole, covering the terminals with some shrinking tubes to prevent them from touching other parts of the device.

as you can see there is a transformer there in the middle of the board! we don't want our leads to touch it in any way.

Step 7: Test and Installation

close the case, plug the female counterpart in your new connector and you will see that when the sonoff goes online and switches on, from your connector you will only get a closed circuit and not any tension, neither AC or DC.

those are the terminals where you will connect the control cables of your heating system... of the pump of a solar powered panel series or whatever you want to control.

for the connections, settings and programming of the th10 refer to the manual included in the box.

have fun and stay safe!

Step 8: Post Scirptum

to make the sonoff work you will only have to connect one cable in N, one in E and one in the Linput holes.

the Loutput will not be used anymore after the modding.