74HC595 8-bit Shift Register

Operating Voltage

2 to 6 V

Supply Current Max

80 µA

Output Drive Current

±6 mA

Input Current Max

1 µA

Clock Frequency Max

29 MHz

Propagation Delay Typical

13 ns

Operating Temperature Range

-40 to 85 °C

Package

PDIP, SOIC, SSOP, TSSOP, CDIP, LCCC

Operates from 2-6 V (per the datasheet specs), so it works at 3.3 V or 5 V. It's a serial-in, parallel-out shift register that adds 8 outputs per chip.

• Expanding digital outputs (LEDs, 7-segment displays)
• Daisy-chaining for many outputs from 3 pins
• Driving relay/transistor banks

• Chain chips via QH' (serial out) into the next SER input.
• Latch (RCLK) after shifting so outputs update together.
• Each output sources/sinks only ~6 mA — use drivers for LEDs strings/relays.

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Community starter examples — minimal, unofficial, and provided to get you wiring fast. Verify against the manufacturer datasheet before relying on them.

// 74HC595 8-bit shift register — community starter example
#if defined(ESP32)
  #define DATA_PIN  23   // SER
  #define LATCH_PIN 5    // RCLK
  #define CLOCK_PIN 18   // SRCLK
#else
  #define DATA_PIN  11   // SER
  #define LATCH_PIN 8    // RCLK
  #define CLOCK_PIN 12   // SRCLK
#endif

void setup() {
  pinMode(DATA_PIN, OUTPUT);
  pinMode(LATCH_PIN, OUTPUT);
  pinMode(CLOCK_PIN, OUTPUT);
}

void loop() {
  for (int i = 0; i < 256; i++) {
    digitalWrite(LATCH_PIN, LOW);
    shiftOut(DATA_PIN, CLOCK_PIN, MSBFIRST, i);   // QA..QH = bits of i
    digitalWrite(LATCH_PIN, HIGH);                // latch to outputs
    delay(100);
  }
}

# 74HC595 shift register (ESP32) — community starter example
from machine import Pin
import time

data  = Pin(23, Pin.OUT)   # SER
latch = Pin(5,  Pin.OUT)   # RCLK
clock = Pin(18, Pin.OUT)   # SRCLK

def shift_out(value):       # MSB first
    latch.value(0)
    for i in range(7, -1, -1):
        clock.value(0)
        data.value((value >> i) & 1)
        clock.value(1)
    latch.value(1)

while True:
    for v in range(256):
        shift_out(v)
        time.sleep_ms(100)