Published May 5, 2025 © GPL3+

74HC595 Shift Register with Arduino UNO

In this tutorial you will explore the working of the 74HC595 shift register and interface it with an Arduino.

BeginnerFull instructions provided2 hours203

Things used in this project

Hardware components

Arduino Uno R3

74HC595 shift register

LED (generic)

Resistor 220 ohm

connecting wires

Solderless Breadboard Full Size

Software apps and online services

Arduino IDE

Story

When working with Arduino, you’ll often find yourself running out of GPIO (General Purpose Input/Output) pins, especially when connecting multiple devices such as LEDs, sensors, or modules. To overcome this limitation and expand the number of output or input pins, shift registers are a reliable and efficient solution.

Understanding Shift Registers

Shift registers are digital memory circuits found in many microcontrollers and digital systems. They are mainly of two types:

SIPO (Serial-In Parallel-Out) – Used to increase the number of output pins. Example: 74HC595.
PISO (Parallel-In Serial-Out) – Used to increase the number of input pins. Example: 74HC165.

In this article, we’ll focus on the 74HC595, one of the most widely used SIPO shift registers. It enables control of 8 output devices using just 3 Arduino pins. Even better, you can daisy-chain multiple 74HC595 chips to expand output control even further.

Whether you’re designing an LED matrix, controlling a display, or building a project that requires multiple digital outputs, the 74HC595 is a go-to component.

Features of the 74HC595 Shift Register

8-bit parallel output
Serial-to-parallel data conversion
Ability to cascade multiple ICs
Low power consumption
Compatible with 5V logic
Operates between 2.0 to 6.0V

Working Principle of 74HC595

The 74HC595 IC consists of two internal registers:

Shift Register: Temporarily holds the serial data.Storage Register (Latch): Holds the final data and updates the output pins.

Data Shifting

Data is fed serially via the SER (Serial Data Input) pin.
Each SRCLK (Shift Register Clock) pulse shifts data one bit left through the shift register.

After loading 8 bits, a HIGH pulse to the RCLK (Latch Clock) pin transfers the data to the storage register.

Output pins (QA to QH) reflect the data in the storage register.

If using multiple 74HC595 ICs, the QH’ (Cascade Output) of one IC connects to the SER pin of the next. This allows you to control 16, 24, or more outputs with the same 3 Arduino pins.

74HC595 Pinout and Functions

QA to QH (Pins 15, 1–7): 8 parallel output pins.
SER (Pin 14): Serial Data Input.
SRCLK (Pin 11): Clock input for the shift register.
RCLK (Pin 12): Latch Clock; moves data from shift register to output.
OE (Pin 13): Output Enable (Active LOW). Connect to GND to enable outputs.
SRCLR (Pin 10): Clears shift register (Active LOW). Connect to 5V for normal operation.
QH’ (Pin 9): Cascade Output for chaining.
VCC (Pin 16): Supply voltage (typically 5V).
GND (Pin 8): Ground.

Interfacing 74HC595 with Arduino

In this section, we will interface a 74HC595 with an Arduino UNO to control 8 LEDs.

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Wiring Steps

Connect Pin 16 (VCC) and Pin 10 (SRCLR) to 5V on Arduino
Connect Pin 8 (GND) to Arduino GND.
Connect Pin 13 (OE) to Pin 9 of Arduino.
Connect Pin 14 (SER) to Pin 11 on Arduino.
Connect Pin 11 (SRCLK) to Pin 12 on Arduino.
Connect Pin 12 (RCLK) to Pin 10 on Arduino.
Connect anodes of 8 LEDs to QA–QH (Pins 15, 1–7).
Place 220-ohm resistors in series with each LED.
Connect cathodes to GND.

To learn how to wire Multiple 74HC595 Shift Registers to an Arduino checkout: Shift Register with Arduino UNO

Arduino Code for Interfacing 74HC595 Shift Register with Arduino

/* 
Code to interface 74HC595 SIPO shift register using Arduino UNO
by www.playwithcircuit.com
*/
//Pin connected to SH_CP of 74HC595
int clockPin = 12;
//Pin connected to DS of 74HC595
int dataPin = 11;
//Pin connected to ST_CP of 74HC595
int latchPin = 10;
//Pin connected to OE of 74HC595     
int brightnessPin = 9;
//Brightness control variable
int PWM_Value = 0;
void setup() {
  //set pins to output so you can control the shift register  and initially they should be HIGH
  pinMode(latchPin, OUTPUT);
  pinMode(clockPin, OUTPUT);
  pinMode(dataPin, OUTPUT);
  pinMode(brightnessPin, OUTPUT);
  digitalWrite(latchPin, HIGH);
  digitalWrite(clockPin, HIGH);
  digitalWrite(dataPin, HIGH);
  analogWrite(brightnessPin, 255);
}
void loop() {
  int led_byte = 0x00;
  //  turn ON all LEDs one by one 
  for (int i = 0; i < 8; i++) {
    // adjust the brightness of LEDs
    PWM_Value = (255 - (115 + (20*i)));
    analogWrite(brightnessPin, PWM_Value);
    led_byte |= (0x01 << i);
    // take the latchPin low
    digitalWrite(latchPin, LOW);
    // shift out the bits:
    shiftOut(dataPin, clockPin, MSBFIRST, led_byte);
    //take the latch pin high so the LEDs will light up:
    digitalWrite(latchPin, HIGH);
    // pause before next value:
    delay(100);
  }
  //  turn OFF all LEDs one by one 
  for (int i = 0; i < 8; i++) {
    led_byte &= ~(0x01 << i);
    // make the latchPin low
    digitalWrite(latchPin, LOW);
    // shift out the bits:
    shiftOut(dataPin, clockPin, MSBFIRST, led_byte);
    //make the latch pin high so the LEDs will light up:
    digitalWrite(latchPin, HIGH);
    // pause before next value
    delay(100);
  }
}

Credits

Rachana Jain

17 projects • 11 followers

I'm an avid Arduino and electronics enthusiast with a passion for tinkering, experimenting, and bringing innovative ideas to life.

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74HC595 Shift Register with Arduino UNO

74HC595 Shift Register with Arduino UNO

Things used in this project

Hardware components

Software apps and online services

Story

Understanding Shift Registers

Features of the 74HC595 Shift Register

Working Principle of 74HC595

Data Shifting

74HC595 Pinout and Functions

Interfacing 74HC595 with Arduino

Wiring Steps

Code

Arduino Code for Interfacing 74HC595 Shift Register with Arduino

Credits

Rachana Jain

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