Smoke detector with gas sensor TGS 813 – source. The simple schematic diagram of a smoke detector presented here utilizes the gas sensor TGS 813 as the main detecting component. The circuit is pretty ...

Humidity Detector Circuit. October 26, 2013 by P. Marian ... You can use other sensors like LDR or NTC instead of the copper ones so you can use this circuit for detecting light or temperature.