Previously, we have posted light controlled digital fan regulator, with which we can control speed of fan remotely from the bed with the help of torch light. Now, here is another light operated project which can also operate remotely from the bed with touch light. The group electronics hobbyist at Dreamlover technology designed and verified a very unique electronic circuit “light-operated internal door latch with which one can close or open the door of your room remotely.”
Circuit Description of Light Operated Internal Door Latch
The circuit of light operated internal door latch is build using control unit and driver unit for the stepper motor. Light-dependent resistor is used here as sensor, whose value is varied according to intensity of light fall on it.
The control unit for stepper motor is build around two timer ICs (IC1 and IC2), NAND gat IC (IC3), 4-bit bi-directional universal shift resistor (IC4), OR gate IC (IC5), NOR gate IC(IC6) hex inverter IC(IC7) and dual D-type positive-edge triggered flip-flop IC (IC8) where driver unit utilize four darlingeton pair transistor (T1 and T2,T3 and T4,T5 and T6,T7and T8) in order to increase the correct capability for operating the stepper motor.
IC1 is here configured as astable multivibrator for time period of 1.5 second. IC2 is configured as monostable vibrator and get trigger from LDR1 when torch light is focused on LDR1.sensitivity of LDR1 is adjusted by potentiometer VR1 to avoid the activation by ambient light LDR1 is covered.