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 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.

This Twilight switch circuit activates a light, a lamp, a motor, etc., at the time of sunset and performs the reverse process at dawn.

This is an ideal circuit for activating a security light that must be on all night.

This darkness detector circuit beeps when the light drops below a certain level.

The main elements of this circuit are the 555 integrated circuit, working as an astable multivibrator and an LDR which is used as darkness sensor.