The SN74HC595 is one of the most useful and popular integrated shift registers: it converts serial data into parallel and provides 8 additional digital outputs using only 3 pins from the microcontroller. It is ideal for Arduino, ESP32, Raspberry Pi, and generally for output expansions in DIY and professional applications.

What is the SN74HC595

An 8-bit Serial-In / Parallel-Out (SIPO) shift register with 3-state outputs. It belongs to the 74HC (High-Speed CMOS) series by Texas Instruments.

Main Features:

• 8-bit outputs (Q0–Q7)
• DIP 16
• Serial input (SER)
• Two clocks:
  • SRCLK: loads the shift register
  • RCLK: transfers data to the output register
• Output Enable (OE): sets outputs to high-impedance
• SRCLR: clears the shift register
• Operating voltage: 2V – 6V
• Output current: approximately ±6–7.8 mA per pin (not for directly driving high loads)
• Clock frequency: up to 24 MHz (depending on Vcc)
• Low power consumption: ~80 μA max

How it works:

You send the 8 bits serially to the SER with pulses on the SRCLK. The data is temporarily stored in the shift register. With one pulse on RCLK, the 8 bits "pass through" to the outputs Q0–Q7. The OE can disable all outputs (tri-state). The SRCLR can reset the shift register to zero.

Ideal for:

• LED bars, LED matrices
• Driving multiple 7-segment displays
• Relays, transistors, MOSFET drivers
• Keyboards, multiplexing
• Any application requiring many digital outputs