Introduction

An Electronic Timer is a circuit used to measure or control time intervals automatically. It is widely used in home appliances, industrial automation, and electronic systems where an operation needs to occur after a specific delay.

This project demonstrates how an electronic timer works using basic components and timer ICs.

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Objective of the Project

The objectives of this project are:

• To design a time-delay control circuit.
• To understand the working of timer ICs.
• To control an output device for a fixed duration.
• To learn timing and delay concepts in electronics.

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Working Principle

The electronic timer works based on the charging and discharging of a capacitor or by using a timer IC (555 Timer).

Using 555 Timer IC

1. The capacitor starts charging through a resistor.
2. When the capacitor reaches a certain voltage, the output changes state.
3. The output remains ON for a fixed time.
4. The timing period depends on the resistor and capacitor values.

Time Delay Formula

T = 1.1 × R × C

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Components Required

Basic Electronic Timer (555 Timer)

• IC 555 Timer
• Resistor (1kΩ – 1MΩ)
• Capacitor (10µF – 1000µF)
• Push Button Switch
• LED / Relay
• Diode (1N4148)
• Power Supply (5V–12V)
• Breadboard & wires

Arduino-Based Timer (Optional)

• Arduino Uno
• Push Button
• Relay / LED
• Jumper wires

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Circuit Diagram

555 Timer-Based Circuit

Pin 1: GND
Pin 2: Trigger
Pin 3: Output ---- LED/Relay
Pin 4: Reset
Pin 5: Control Voltage
Pin 6: Threshold
Pin 7: Discharge
Pin 8: VCC

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Arduino-Based Circuit

Push Button ---- D2
Output Device -- D8
GND ----------- Common Ground

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Arduino Code (Optional)

int buttonPin = 2;
int outputPin = 8;

void setup() {
  pinMode(buttonPin, INPUT);
  pinMode(outputPin, OUTPUT);
}

void loop() {
  if (digitalRead(buttonPin) == HIGH) {
    digitalWrite(outputPin, HIGH);
    delay(5000); // 5 seconds delay
    digitalWrite(outputPin, LOW);
  }
}

Code Explanation

• When the button is pressed, the output turns ON.
• After a fixed delay, the output turns OFF automatically.
• Delay time can be changed in the code.

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Advantages

• Accurate time control
• Simple circuit design
• Low power consumption
• Wide range of timing intervals

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Applications

• Automatic lighting systems
• Washing machines
• Industrial control systems
• Traffic light timers
• Home automation

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Conclusion

The Electronic Timer is a versatile and essential electronics project that helps in automating time-based operations. It is ideal for beginners and can be expanded using microcontrollers, displays, or IoT integration.