Using Pulse Wide Modulation with Three MQ Sensors to Monitor Synthetic Gas Composition with an Arduino Uno3

Commercial gas analyzers are not suited for long time usage and relatively too costly for institutions in underdeveloped countries. Metal oxide sensors have emerged as simple and reliable sensors for gases concentration measurements at an affordable cost. For gasification, carbon monoxide, hydrogen and methane concentration must be monitored at the same time. Hence the need for using three different gas sensors at the same time. SnO2 based sensor are of SnO2-based gas sensors have been broadly studied to take advantage of the variation of the resistance of metal-oxides thin films. These sensors exhibit a resistor that depends on the nature of the gas flowing between its pins and its concentration in the flue gas. SnO2-based gas sensors have a special heating requirement that must be correctly addressed to have meaningful results. This paper reports the methods used and the results obtained to fulfil that heating requirements for three SnO2 sensors at the same time while avoiding power consumption peaks. Using the Pulse Wide Modulation Technique, we have simultaneously synchronized the heating cycle requirements of three MQ family SnO2-based sensors to estimate the concentration of carbon monoxide, hydrogen and methane in synthetic gas produced by a wood-fired co-current downdraft gasifier.