This circuit toggles a miniature relay when you touch the sensor plate with your finger.

No IC is used and it is good for showing how transistor flip-flop works.

This circuit controls the ON/OFF of a miniature relay according to the intensity of light sensed by the CDS photo resistor.

Relay is ON under bright light and is OFF in the dark.

* Sensitivity is adjustable.

A very reliable sound actuated switch that turns a relay ON or OFF when it detects hand-clapping sound.

An active band-pass filter is included to filter out voice and other low frequency noises.

This timer has two buttons.

Pressing "START" button briefly, a relay will turn ON for a preset time set by a potentiometer.

Pressing "STOP" button will immediately stop timing and reset the relay to OFF state.

This sensor detects moving objects (visitor, burglar) by means of ultrasonic wave.

The circuit turns ON a relay when any object is moving within the detection area.

Lock it by pressing any key. To unlock, you need to enter a 3-digit code correctly.

Relay is energized when the lock is in the locked state.

Lock it by turning on the circuit. To unlock, you need to turn off the circuit within 15 seconds.

Relay is energized when the lock is in the locked state.

The transmitter sends out a tone-modulated radio wave of 300MHz (UHF).

When the receiver receives this signal, a relay will be turned on, for as long as the transmitter is in operation.

The transmitter emits a tone-modulated 38K~ 40 KHz invisible IR beam.

The IR receiver module on the receiver unit detects the beam and actuates a relay.

* Can operate in the momentary or toggle mode.