Description: This is an optocoupler I2C board. It is a board for remote 8-input expander for I2C bus based on PCF8574. Making it ideal as an isolation input expander for I2C bus. It is designed to compatible with almost 3.0V to 5.5V microcontrollers.

The PCF8574 is the I2C bus expander chip which talks to microcontroller and then reads status of input voltages from optocouplers. It supports 100kHz bus frequency. And it can be connected to 3.0V to 5.5V of I2C port of microcontroller. Normally the I2C bus needs pull-up resistors for pulling-up SDA and SCL lines. The board has these resistors and jumpers. These resistors can be enabled or disabled by the jumpers.

The board has an interrupt output signal. On this line, the board can inform the microcontroller if there is incoming voltage on its inputs. The interrupt pin is open-drain so it needs pull-up resistor. This resistor is presented on the board and it is enabled or disabled by a jumper.

The board has 8 optocouplers for input voltages. Each input supports high level logic 3.0Vdc to 30Vdc. However the inputs of the board can accept more than 30Vdc but they need external resistors.

The board is addressed by 3 jumpers to make 8 different addresses. So that 8 boards can be connected together on the same bus. Moreover 16 boards can be connected together on the same bus when they have 16 different addresses. So, 8 boards of the PCF8574 and 8 boards of the PCF8574A can be connected together on the same bus because the PCF8574 doesn't have the same address as the PCF8574A.

The board has inverse polarity protection circuits to prevent damage from a mistake of connection. Also the board has an LED to show status of the power supply input voltage.

The board is designed for small size. The size of PCB is 28x81.5mm.

The I2C-IN830S and I2C-IN830SA models differ only in their I2C chip which they also differ in slave address.
The I2C-IN830S and I2C-IN830SA can replace the EI2C-9AG and the EI2C-9AGA respectively.

  • PCF8574, I2C bus chips
  • Support 100kHz I2C bus frequency
  • Selectable I2C bus pull-up resistors
  • Address by 3 jumpers for use of up to 8 addresses
  • Up to 16 boards on the same bus
  • Interrupt output signal
  • Selectable interrupt pull-up resistor
  • Compatible with almost microcontrollers
  • 8 Optically isolated digital input channels
  • 3.0Vdc to 30Vdc input voltage
  • More than 30Vdc can be accepted by adding external resistors
  • 3700Vdc isolation input voltage
  • Operating power supply voltage 3.3V to 5.5V
  • Inverse polarity protection circuits
  • Small board, PCB size 28x81.5mm
Documents: datasheet, schematic, pcf8574

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