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Automation is now integral to daily life, with mobile phones serving as essential tools. This device employs a mobile phone torch to control domestic appliances, exemplifying an efficient light-operated switch. By responding to light intensity, it activates or deactivates appliances with ease.
The switch detects ambient light through a light-dependent resistor (LDR) or photodiode. A focused beam from a mobile torch, standard torch, or laser torch triggers the system—powering the appliance on with the first focus and off with the second.
The LDR sensor in the circuit translates changes in light intensity into electrical signals, driving the switching mechanism.
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With versatile applications, this device can be handy for individuals with physical disabilities, enabling effortless appliance control. It is equally effective for managing indoor and outdoor lighting in homes. Fig. 1 shows the author’s prototype on a breadboard.
Parts List |
Semiconductors: IC1 (IC1A-IC1B) – LM358 op-amp IC2 – 4017 decade counter T1 – BC337 NPN transistor D1 – 1N4007 rectifier diode LED1 – 5mm red LED Resistors (all 1/4-watt, ±5% carbon): R1 – 100kΩ R2, R3 – 4.7kΩ R4, R5 – 1kΩ Capacitor: C1 – 1μF, 25V electrolytic Miscellaneous: RL1 – 12V, SPDT relay CON1-CON3 – 2-pin connector LDR1 – Small light-dependent resistor – 12V battery – Mobile phone/torch or laser light – Appliance (60W 230V AC bulb) |
Light-Activated Switch – Circuit and Working
Fig. 2 shows the light-operated circuit diagram to switch on/off appliances. The system is built around dual op-amp LM358 (IC1), decade counter IC 4017 (IC2), a 12V single-pole double-throw relay (RL1), and a few other components.
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