Sonoff Basic Rebuild to Low Voltage (12V)

Hello guys. Wouldn' t it be nice sometimes to control all your appliences and all your stuff with a WiFi smart switch? But often you don' t need to switch 230V AC. If you create a Short Circuit during wiring theres a risk of an electric shock - This can be very dangerous! I looked for a way to switch on/off my LED Strips using a Sonoff without switching 230V of the power supply. So in this Instructable I'm going to show you how to create your very own WiFi Smart Switch for voltages up to 35V DC using only a few components:

-1x SONOFF BASIC 100-230V 10A: https://letyshops.com/r/gearbest-4hoak29358kkco

-1x Small PCB (I cutted a piece of a 2x8cm PCB)

-1x L7805 Voltage Regulator

-2x 103 (10nF) capacitor

-cables (I used 0.14mm²)

-Some solder

Tools:

-Soldering Iron

-Rotary Tool, but a cutter would also do the job as fine :)

So let' s begin!

If you don' t understand some steps, please feel free to ask and watch my YouTube Video!

Stay Creative! ;) ;D

Step 1: Disassemble the Sonoff

Take the Sonoff out of it' s cover. This step should be very easy :) You have to strip of the warranty sticker. The warranty will be lost after this Modification!

Step 2: Locate the Voltage Regulator

You have to find the Voltage regulator. This regulator steps down the +5V to +3.3V for the ESP8266. You can find the regulator (btw. a AMS1117) on the back of the PCB. It is very tiny ;)

Step 3: Soldering Part 1

Now you have to cut two lenghts of 0.14mm² cable. I used about 10 cm, because I wanted to 3d print an enclosure for the new PCB at first, but I later decided to put all the components inside the old housing. Therefore I recommend to use e.g. 5cm. This should be definitely enough. Then you have to solder the red cable (+) to the right terminal of the voltage regulator. The black Minus-wire will then be connected to the left port of the AMS1117. This step would be easier if you tin the cables at first.

Step 4: Making the New PCB

Now you have to cut a small piece out of the PCB. Make it as small as possible. I used my Rotary Tool for this. Of course you can use an oldschool cutter :). Solder the circuit as shown in the scematic and hook the Input wires up to the Input terminals of the SONOFF Basic! Look at the video if you don' t understand what I am talking about :)

Step 5: Cutting the PCB Tracks (Optional)

If you want you can cut the tracks of the PCB that are going to the old transformer (230V to low voltage). You can use for example a cutter or your Rotary Tool to do this.

Step 6: Have Fun!

After closing up the housing you can use it as before, only with the difference that your modified version only can handle up to 35V DC :) Enjoy it ;D

Comments

[durval]

Shouldn't the relay be replaced too, by a proper DC relay?

DC circuits make electrical arcs that need much more robust contacts. Using AC relays for DC switching usually results in a much shortened operating life

[dvdmerwe]

This is just what I have been searching for (or using the Sonoff SV possibly) but what I wanted to know is does anyone know how the max load is effected at 12V? I know its spec sheet says 10A but that was at 250V. The reason why is that I'd like to use this inline between a 12V max 20A battery charger and the battery.

[idIoT3D]

Hi dvdmerwe, I think the maximum amps would still be limited to 10 amps, because the relay is only rated up to 10A! I would use an ESP8266 in addition to a high power relay and Tasmota for this. I already did this for one of my 3D-printers, which draws around 25-30A at 12V. 20A would definitely be too much for this small relay! Hope that helps ;)

[dvdmerwe]

Thank you yes that helps.

[NikolasT1]

Is that possible to make it for up to 35V AC ?

[idIoT3D]

Hi, yes of course! You only need to rectify the voltage from AC to DC using a full bridge rectifier in front of the voltage regulator! So in your case the traces don't need to be cut, you only need to connect the DC output of the rectifier to the AMS and the switching voltage would still be 35V AC! :)

[fabiomvs]

I actually have the same question. In irrigation systems you find it often 24VAC valves that you need to switch. Otherwise I would need a buck converter to convert 220VAC to 24VAC or I should use Sonoff SV instead. Thank you.

[cagriyilmaz]

I couldn’t get the soldering on the back of the pcb you’ve added. Are there paralel, straight, soldering lines connects everything along the straight line at the back?

[cobunn]

I also have broken that button switch. Can you show its wiring/ schematic/ or description? Or have you completed another video about the switch?
Thanks for your 12v hack.

[gctseng]

Awesome mod! I have a question regarding your choice for capacitance values. The datasheet has a reference design that seems to require much higher values. Can you provide any comments so I can understand? Thanks. Looking forward to modding a couple of Sonoffs but wanted to clarify so I can order the right parts.

[idIoT3D]

Hi gctseng,
I recommend to refer to the values provided in the manufacterers datasheet! Idk exactly why I used those values but I tested the circuit with those values and seems to work all the time.
Sorry for my late reply,
Felix :)

[kasun75758]

Great article.Thank you very much.

[JayA119]

This looks like the source voltage is now low voltage.

Do you have a way to connect to the mains, but just close an isolated N.O. switch to control low (
A friend wants to control her gas fireplace, but the wall switch is just interrupting the 24v transformer output to a relay.

It is a 2-gang box and 120v mains is available for the sonoff, but I don't want to send that down the relay line

[Felix RafaelB]

https://www.youtube.com/watch?v=p76OQI5Xx2k

[JimJtron]

Have added photos to show where I soldered and show some ebay modules that are pre-built to drop 12v down to 5 v. For isolation from the AC voltage input circuit, I removed the diode bridge and PTC blue disc component. Hope this helps. Regards, Jim

[JimJtron]

Gidday Mate.

Great article.I can confirm that the 5 volt mod works on the Sonoff RF as well but I soldered my wires a little different.In your Step2 picture, your red circle passes over a square hole.

that is where the RF Receiver module picks up the ground.I found it easy to solder my ground wire there.The 5 volt wire was soldered to the Electro capacitor’s positive lead after tracing the track from the regulator.It’s just to the left of your red circle.It’s easier to solder there I think.Also because the heat from the soldering iron could damage the regulator, I recommend these alternative ‘safer’ solder points.Also discovered that the RF version can learn 2 seperate keyfob transmitters. Anyway, Well done on the article and video.
Regards, Jim

[AndresM169]

hola me di cuenta que el boton se daño como ami se me arrancaron las pistas como puedo reparar el boton gracias

[maxouille34]

Hello . I'am french and it is exactly what i search . Could you tell me if it was the same way to a sonoff 4ch v2 ? I have bought one and search to connect only 24v I think it was the same system , i must search the regulator voltage +5vdc and ground .Thanks

[idIoT3D]

Hello, I have never bought or seen an sonoff 4ch v2. I have searched on the internet and looked for pictures of your model. But the pictures are too small and I can' t read the text written on the components or on the PCB. What you could do by yourself is sending me a picture (close shot) of the PCB. I will help you to find a solution for this purpose. If you want to do it yourself, you can power it up through the 5,5*2,1mm-Port and measure with a multimeter on the PCB to search 5V. You have to do this WITHOUT plugged in 230V!!!!! The relay-terminals should not be connected to any voltage (230V/110V/...). You do this at your own risk! Greetings from Germany to France ;)

[maxouille34]

Hello . Here is 2 pics of the pcb i think it was the same like the Sonoff basic . thanks