Lie detector circuit using two transistors

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

This temperature to voltage converter circuit, convert the sensed temperature by a thermistor into a voltage level.

The circuit achieves an acceptable performance between 0 and 24°C

This simple humidity sensor circuit using a 555 timer, shows us the humidity level that a ground under test has. To achieve the goal, a couple of probes are used.

These probes are placed on the ground to be tested.

Temperature gauge circuit using the LM324 IC

The temperature level is displayed using 4 LEDs:
A green LED indicates that the temperature is OK.
Two yellow LEDs indicate that the temperature is higher than normal.
A red LED indicates that the temperature is very high