For measuring the air quality in the living room I was looking for a CO2 sensor to build my own CO2 Iot node. Looking around on the internet I found the MH-Z19<\/a> sensor, not that expensive and according to other users this sensor is accurate.<\/p>\n A new project was born. The MH-Z19 was combined with a\u00a0BME280<\/a> and TSL2561<\/a> so we can measure lux, temperature, humidity, air pressure and CO2 with one Iot node in the living room and send everything over Mqtt to Node-red for further handling and Sqlite database storage. <\/p>\n
\nThe biggest part of the design is a copy of my Iot Bme280 sensor<\/a> module, this Iot sensor runs 40 days on one 18650 li-ion cell. However the MH-Z19 requires 5V and uses a lot more current so I thought it would be nice to power it from a power bank.
\nThe esp8266 requires 3.3V so the 5V from the powerbank is stepped down with a PAM2305AAB330<\/a>, very interesting stepping regulator that only requires 2 capacitors and 1 inductor. Little bit hard to get here in Europe, but luckily Arrow had “no shipping charge” days and the parts where quick and cheap here.
\nThe MH-Z19 requires serial communication with the esp8266, the last one has power enough to do this with a software uart. Example for the Arduino IDE<\/a> to get data out of the MH-Z19 was also quickly found. With all of this together the data was quickly streamed to the Mqtt broker.
\nThe pcb was designed so that it will fit inside a Hammond 1591 case and the pcb is used like a sort of front panel this way. The MH-Z19 is milled out the pcb so you can mount it on the back.<\/p>\n