Contains a laser and sensor. Appears to detect light scattered by particles that pass the laser beam. Air forced through channel by a fan.

Manual

DC power input 12V centre positive. With added ESP8266, draws about 300mA peak on start, then 200mA steady. The board gets pretty warm for some reason.

Clock battery: CR1220s 3V.

I have modified the one I had. When I got it, it was already a bit broken. Fan disconnected and no main battery. I replaced the fan. I added an ESP8266, which is connected to the UART output of the PIC to read the measurements. I didn't connect a line the other way. I expect it will need to be calibrated for the new fan and changed wiring / battery removal etc. as it will have affected the airflow.

The external serial port is not connected to anything.

9600 baud, 8N1.

Output is small particle count, large count, CRLF.

“This data is output every minute and the counts represent the average concentration over the past minute. The units are – counts/100 per cubic foot. In the above example, the output of 675 would mean the average concentration over the past minute was 67,500 particles per cubic foot.” (manual)