Sometime ago I bought an IKEA smoke sensor. It lived some time in the kitchen as expected, but then I put next to my 3D-printer that was located in the garage.

But then, it doesn’t make a lot of sense if it only fires an alarm in case of smoke, since I maybe away, so I decided to hack it into something IoT.

There are a couple of useful blog (this and that) posts that I started from.

It took quite a while to just follow the advice given there and to solder properly ground connection to the CS2105G0-S12 chip (that people suggest is actually MC145012). Anyway my project is a bit simpler in a way – the wi-fi module (Wemos D1 mini) is constantly powered with USB and feeds data every second to Blynk.

One other issue I had was that smoke sensor IC is using 9V for power and signals, so it had to be stepped down. With invaluable help from my former colleague Mich, I did it using an NPN transistor and it works pretty smoothly.

Printed a special case for it to fit all the components.

In case of smoke the Blynk app will send me a notification. Later on, it will also turn off the smart socket that the printer is powered with.

Arduino source is on Github. I will try to put some more details and the scheme later.

I have no illusions that this thingy is pretty weak in terms of safety and reliability – there are too many things to break in case of a real fire – but it was an important learning project for me.