MUD LED Headlight dimmer Sunil Negi

Code for LDR testing : -

int ldrPin = 2;      // LDR module digital output

int relayHigh = 8;   // Relay 1 - High Beam

int relayLow  = 9;   // Relay 2 - Low Beam

void setup() {

  pinMode(ldrPin, INPUT);

  pinMode(relayHigh, OUTPUT);

  pinMode(relayLow, OUTPUT);

  // Default condition - Low Beam ON

  digitalWrite(relayHigh, LOW);

  digitalWrite(relayLow, HIGH);

}

void loop() {

  int ldrState = digitalRead(ldrPin);

  if (ldrState == LOW) {

    // Bright headlight detected → Switch to LOW Beam

    digitalWrite(relayHigh, LOW);

    digitalWrite(relayLow, HIGH);

  } else {

    // Normal dark road → Switch to HIGH Beam

    digitalWrite(relayLow, LOW);

    digitalWrite(relayHigh, HIGH);

  }

  delay(100);

}

✅ 1. LDR Module Pin Description (3-pin type)

A typical LDR module has these pins:

LDR Module Pin	Description	Connect To
VCC	+5V supply for module	Arduino 5V
GND	Ground	Arduino GND
DO (Digital OUT)	Becomes LOW when bright light hits the LDR; HIGH when dark	Arduino D2

(DO threshold is adjusted using the onboard potentiometer.)

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✅ 2. Relay Module Pin Description (2-channel)

Relay module pins:

Relay Pin	Description	Connect To
VCC	5V relay coil supply	Arduino 5V
GND	Ground	Arduino GND
IN1	Controls Relay 1	Arduino D8
IN2	Controls Relay 2	Arduino D9

Relay screw terminals (for each relay):

Terminal	Meaning
COM	Common
NO	Normally Open (connected when relay ON)
NC	Normally Closed (connected when relay OFF)

We will use COM and NO only.

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⚡ Bike Headlight Wires (Typical)

Bike Wire	Function
White	High Beam
Blue / Yellow	Low Beam
Green / Black	Ground

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⭐ Complete Step-by-Step Wiring Guide

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🔹 STEP 1: LDR Module → Arduino

LDR Pin	Arduino
VCC	5V
GND	GND
DO	D2

DO pin logic:

• Bright incoming headlight → DO = LOW

• Normal dark road → DO = HIGH

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🔹 STEP 2: Relay Module → Arduino

Relay Pin	Arduino
IN1	D8
IN2	D9
VCC	5V
GND	GND

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🔹 STEP 3: Bike Headlight → Relay (2-Relay Method)

We are supplying +12V to the relays, each relay powers one beam.

Relay 1 → High Beam

• Relay1 COM → Bike +12V (through a fuse)

• Relay1 NO → High Beam wire (White)

Relay 2 → Low Beam

• Relay2 COM → Bike +12V

• Relay2 NO → Low Beam wire (Blue/Yellow)

Ground Wire:

• Headlight ground wire → Bike chassis ground
  (No connection to relays)

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🔹 STEP 4: Arduino Power

You must power Arduino using:

✔ USB 5V powerbank
OR
✔ Bike 12V → 5V converter (buck converter)

DO NOT connect bike 12V directly to Arduino 5V pin.

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✔ Working Logic

• When another vehicle shines light → LDR module output becomes LOW → Arduino activates Relay 2 → Low Beam.

• When road is dark → LDR module output becomes HIGH → Arduino activates Relay 1 → High Beam.