LDRs or Light Dependent Resistors are very useful especially in light/dark sensor circuits. Normally the resistance of an LDR is very high, sometimes as high as 1000 000 ohms, but when they are ...

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 ...