This simple lie detector consists of two transistors and other additional components and can detect if a person does not tell the truth (the person is lying), using two sensors placed directly on the skin.

This circuit convert the sensed temperature by a thermistor into a voltage level. The circuit achieves an acceptable performance between 0°C and 24°C

This simple humidity sensor circuit, shows us the humidity level that a ground under test has. To achieve the goal, a couple of probes are used.

The temperature gauge circuit is implemented using four comparators. We use the LM324 integrated circuit, which has four 741 operational amplifiers (op amps) in a single package.