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ELECTRONICS

AT89S52 16-Relay Board with PCF8574 I2C Expanders

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UPDATED 2026-08-01
TYPECircuit
USE-CASEAt89s52 Relay Board
EXAMPLEAT89S52 16-Relay Board with PCF8574 I2C Expanders
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CASE ANALYSIS

Scenario

An AT89S52-based 16-relay control board using PCF8574 I2C I/O expanders and ULN2803 Darlington arrays to drive relays while minimizing MCU pin count.

Key decisions

  • Used PCF8574 to convert I2C to 8-bit parallel output, reducing microcontroller I/O usage.
  • Integrated ULN2803 with common freewheeling diode connection to simplify relay coil protection.

When to reuse this

Ideal for home automation, industrial control, and prototyping requiring high relay count with limited MCU pins.

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