Tuesday, February 25, 2025

Control Home Appliances with a Mobile Torch: DIY Light-Activated Switch Using LDR

efy test

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.

- Advertisement -
Breadboard setup for DIY Light-Activated Switch Using LDR
Fig 1: Author’s prototype of DIY Light-Activated Switch Using LDR

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 SwitchCircuit 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.

EFY++ CONTENT: ACCESS TO THIS CONTENT IS FREE! BUT YOU NEED TO BE A REGISTERED USER.

- Advertisement -

Oops! This is an EFY++ article, which means it's our Premium Content. You need to be a Registered User of our website to read its complete content.

Good News: You can register to our website for FREE! CLICK HERE to register now.

Already a registered member? If YES, then simply login to you account below. (TIP: Use 'forgot password' feature and reset and save your new password in your browser, if you forgot the last one!)

SHARE YOUR THOUGHTS & COMMENTS

EFY Prime

Unique DIY Projects

Truly Innovative Electronics

Electronics News

Latest DIY Videos

Electronics Components

Electronics Jobs

Calculators For Electronics