Auto light switch for bathroom using laser and IC4017
Many people forgets the bathroom and toilet lamps in ON state, absolutely this causes increasing electric bill and even decrease lamps lifespan. This circuit is a simple way to turning ON and OFF the bathroom or toilet lamp automatically without using microcontroller. The circuit based on the counter IC4017 and laser. when a person go to bathroom his body cut the laser ray that is focused on the LDR in another side of the door frame, connecting and disconnecting the laser ray changed the LDR electric resistance and giving a positive signal to pin14 of the IC4017 through transistor 2N2222, since pin4 jumped to reset pin (pin15) so the output selector will be changed between pin3 and pin2. Pin3 run the transistor to running the relay. Two LEDs showing ON state and OFF state. 330 ohm resistor used to LEDs protection by giving 15mA current to them. You can use any other NPN transistor rather than 2N2222 such as BC547, C9013, 2N5551, etc. This circuit is suitable for light switching for an