David A Riewe
Published © CC0

Playing night rider with three 74HC595s

Who isn't fascinated with shift registers and blinking LEDs? Using the 74HC595 I'll show you how to control 24 LEDs with three pins.

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Playing night rider with three 74HC595s

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Code

Night Rider Code

C/C++
/*
Using three 74HC595s to control 24 leds (outputs) on the arduino uno. 
This is an improved version by John Rogers
*/

int latchPin = 5;   // to pin 12
int clockPin = 6;	// to pin 11
int dataPin = 4;	// to pin 14

int numLights=24;
unsigned long light = 0;  // Bit pattern for entire display
byte b1 = 0;				// byte place holders for each shift register
byte b2 = 0;				// extracted from "light"
byte b3 = 0;

	

void setup() 
{
  pinMode(latchPin, OUTPUT);
  pinMode(dataPin, OUTPUT);  
  pinMode(clockPin, OUTPUT);
 // Serial.begin(9600);
}

void loop() 
{
	for (int i = 0; i < numLights*2; i++)
	{
		int shift = i;
		if( i >= numLights )	//if i is above numlights then wee need to start
		{						// moving back to the left.
			shift = numLights*2 - i - 1;
		}
		// Extract the bytes of the light patter to be sent out
		light = (long)(1)<<shift;
		b1 = (byte)((light>>16)&0xFF);
		b2 = (byte)((light>>8)&0xFF);
		b3 = (byte)((light)&0xFF);
		updateShiftRegister();	// shift out b1, b2 and b3
		delay(30);
	}
}

void updateShiftRegister()
{
   	digitalWrite(latchPin, LOW);
   	shiftOut(dataPin, clockPin, MSBFIRST, b1);
   	shiftOut(dataPin, clockPin, MSBFIRST, b2);
   	shiftOut(dataPin, clockPin, MSBFIRST, b3);
   	digitalWrite(latchPin, HIGH);
   	
}

nightrider.ino

Credits

David A Riewe

David A Riewe

8 projects • 21 followers
Engineering Tech who enjoys hacking electronics, learning about new devices and programming. Founder of HackerSpaceTech

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