Hanwei/Winsen and SGX Sensortech produce a range of sensors for gas detection and measurement. This project demonstrates how to use the MQ-3 and MiCS-5524 sensors. These are based on a heated, metal oxide semiconductor which varies in resistance in the presence of a gas or vapour that can be oxidised - this includes some hydrocarbons, alcohols, ammonia and carbon monoxide. This change of sensor resistance can easily be determined from an on-board potential divider circuit producing a voltage. That voltage can be measured on an analogue (ADC) input.
In this project a Circuit Playground Express (CPX) board is used, but any board with two analogue inputs could be used.