I am looking for a CO Sensor, preferable homematic, shelly or tasmota.
I use this
Sorry to say that it’s Z-Wave connected
I put a Sensirion SPS30 and a Sensirion SCD40 together with an ESP-01S into an IKEA Vindrikting. A bit of a diy-project, but lots of fun, and I learned a lot along the way. Plus the CO2-Sensor is industry-grade.
More details here: IKEA Vindriktning Air Quality Sensor - #409 by Goram - Share your Projects! - Home Assistant Community
We use this one
Why not look in those projects compatible devices?
The sensirion ones are a popular choice. AliExpress is your friend.
The problem, if we are really talking about a CO and not a CO2 sensor is, that there is hardly anything in the market. The device @smitopher linked to, has this little “This item is discontinued” on the page, and the sensors @Cplant linked to, are a particle matter and a CO2 sensor but no CO sensors. Just the sensor @Mclupo linked to, is a CO sensor, but it is quite expensive ~ € 140,-- and it is not wireless and you could just get the contacts to connect to “something else” to get an alarm, that the threshold of the sensor is reached.
On the list linked by @Pedro_Liberal, I found the Adafruit BME680 - Temperature, Humidity, Pressure and Gas Sensor [STEMMA QT] : ID 3660 : $18.95 : Adafruit Industries, Unique & fun DIY electronics and kits I did not find when I was looking for a CO sensor (maybe it came later, as there is a note “the long awaited …”. It is worth taking a look at. I never used Tasmota, but as it is I2C and SPI it will also work with arduino, Raspberry Pi, …
I used a MQ7 “flying fish” board instead that works more or less, as you will find some critics online, stating that the “flying fish” cannot work exactly as it does not allow the necessary heat and cool down cyclus the sensor needs. And you will find this subject also adressed for the BME680 and you will also find a note there, that these sensors are not calibrated and that calibration to known concentratitons is necessary to get exact readings. So, this is something not so easy. For example, I followed some examples I found for calculation of a ppm value from the resistance of the sensor. These did not work for me. Instead I just let my sensor run for a while and adjusted the threshold to something that is not reached under normal conditions. But the sensor also has a little “desire” to run up over the time. So I do normally a reset after I got an alarm after some weeks the sensor was “on duty” as you can see in the graph below:
But nevertheless I like to have at least some reading of CO and an alarm much below everything really dangerous. And the advantage of the “flying fish” is, that I built my device in a way that I can simply plug in a new “flying fish” for little money when the sensor reaches and of life. Until I had this device I had to by dumb CO sensors every ~5 years for about € 30,–.
Since there are no conectable CO Sensors around, I used a cheap China CO warning Sensor and connected it with a Shelly Uni. I works fine.
If someone is interessed I can give more information.
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I would be interested in more details like the exact model and what you get from it. From the wiring it looks like you pick up the signal of the buzzer and report to OH when it is powered to sound. Is that right?