Pressure Switch

A simple pressure switch with a range of 50 to 350 mbar can be made using a pressure sensor. If you can accept somewhat reduced linearity, the sensor can even be used up to 500 mbar. As shown in the schematic diagram, the circuit contains very few components other than the sensor. D1, R1, C1 and D5 form a simple voltage stabiliser that holds the supply voltage for the sensor and opamps at 5 V. The three diodes in series with the sensor provide temperature compensation (more on this later).