Automatic Bathroom Light On/Off Switch Control Circuit Diagram

Hi, in this article, we are going to see the Automatic Bathroom Light On/Off Switch Control Circuit Diagram and wiring procedure. The automatic bathroom light on/off switch control system is a smart home solution that uses sensors to detect the presence of a person in a bathroom and control the lighting accordingly. The system automatically turns on the lights when someone enters the bathroom and turns them off when they leave the bathroom. This control system can be built using various technologies such as motion sensors, infrared sensors, or ultrasonic sensors but in this article, we will learn how to make it with Reed Switch and a few electronic components. It may be the simplest method than others.

Advantages of Automatic Bathroom Light On/Off Control

1. One of the most significant advantages of an automatic bathroom light control system is energy savings. Lights are only on when needed, which reduces electricity consumption and helps lower utility bills.
2. Users do not need to manually switch the lights on or off, so it is very convenient. The system provides hands-free operation, so it is very useful for older people, children, or individuals with disabilities.
3. As the lights are automatically turned on when someone enters the bathroom, the system helps prevent accidents or falls that could occur in the dark. It also helps to avoid the potential hazards of touching electrical switches with wet hands, reducing the risk of electric shock.

Automatic Bathroom Light On/Off Switch Control Circuit Diagram

Here, you can see the circuit diagram of the Automatic Bathroom Light On/Off Switch Control.

Component List

• Magnetic Reed Switch - 1 Pcs
• Decade Counter IC CD4017 - 1 Pcs
• OpAmp IC741 - 1 Pcs
• Transistor BC547 - 1 Pcs
• Transistor BC556 - 1 1 Pcs
• Voltage Regulator IC 7805 - 1 Pcs
• 9V DC Relay - 1 1 Pcs
• 1N4007 Diode - 1 1 Pcs
• 220V/230V Bulb - 1 1 Pcs
• Resistor 10 Kilo Ohm - 2 Pcs
• Resistor 100 Ohm - 1 Pcs
• Resistor 820 Ohm - 1 Pcs
• Resistor 330 Ohm - 1 Pcs
• 230V AC/9V DC Power Adapter
• 230V AC Power Supply

Connection Description

Power Supply Connection

The 230V AC/9V DC power adapter is used to step down the 230V AC from the mains to 9V DC. This 9V DC will be used to power the circuit. It is directly applied to the 9V Relay and through the IC7805 to the rest circuit.

Voltage Regulation

The output of the 9V DC power adapter is connected to the input pin (pin 1) of the 7805 voltage regulator. This will provide a stable 5V output from pin 3 of the 7805, which will power the ICs (CD4017 and IC741) and other components in the circuit. The ground pin (pin 2) of the 7805 should be connected to the common ground of the circuit.

Magnetic Reed Switch Connection

One terminal of the magnetic reed switch is connected to the 5V supply from the 7805 voltage regulator and the other terminal of the reed switch is connected to one input pin of the OpAmp IC741 (non-inverting input, pin 3) through the transistor BC556. The transistor BC556 helps to strengthen the signal of the reed switch.

OpAmp IC741 Connection

The output of the OpAmp IC741 (pin 6) is connected to the clock input of the CD4017 IC (pin 14). The inverting input (pin 2) of the OpAmp IC741 is connected to a voltage divider network formed using two 10 kΩ resistors and ground. This sets a reference voltage. The OpAmp will amplify the small signal from the reed switch and provide a proper logic-level signal to the CD4017.

Decade Counter IC CD4017 Connection

The reset pin (pin 15) of the IC is connected to the ground. The output pin (pin 2) of the CD4017 will provide a signal to the base of the BC547 transistor via a 330Ω resistor.

Relay and Load (Light Bulb) Connections

The collector of BC556 is connected to one end of the relay coil and the emitter is connected to the Negative or Ground Terminals of the power supply.

The other end of the relay coil is connected to the 9V power supply. This will energize the relay when BC556 is activated.

The relay’s normally open (NO) contacts are used to control the 230V AC power supply to the 220V/230V light bulb. So, one terminal of the AC supply is connected to one side of the bulb, and the other terminal of the bulb to the NO contact of the relay. The common (COM) contact of the relay should be connected to the other terminal of the AC power supply.

The 1N4007 diode is connected across the relay coil (cathode to the positive supply) to protect the circuit from voltage spikes when the relay coil is de-energized.

Working Principle

When the magnetic reed switch is activated (when the door is opened), it sends a signal to the OpAmp IC741.

The OpAmp amplifies this signal and triggers the CD4017 counter, which sends a signal to the BC547 transistor.

The BC547 transistor activates the relay.

The relay closes its contacts, turning on the 220V/230V light bulb.

When the reed switch deactivates (when the door is closed), the reverse process happens and the light will turn off.

Read Also: 

• Remote Control Switch Board Internal Circuit Diagram
• Simple Door Security Alarm Circuit with Magnetic Reed Switch
• IR Remote Control Light (On/Off) Circuit Diagram
• Auto On Off Night Lamp (230V) Wiring Diagram and Connection
• Motion Sensing Light Circuit Diagram and Connection Procedure

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