Four Relays Four Inputs
8-Layer Stackable Card
for Raspberry Pi


This board is replacing the 4-Relays board, adding four universal inputs and an RS485 port. Currently in production, stock expected mid-March. Two fully functional prototype samples can be ordered and shipped right now.

  • Four RELAYS with status LEDs
  • Four universal opto-isolated inputs with status LEDs
  • Eight layer stackable to 32 relays and 32 inputs
  • Pluggable connectors 30-16 AWG wires
  • NO and NC contacts on all relays
  • Switch loads of up to 8A and 240V
  • Read AC and DC, 3V to 240V inputs
  • Software self-test
  • Command Line and Python Drivers

Available on backorder


4 Relays 4 Inputs for Raspberry Pi: Drive 8A/240VAC loads and read 3V to 240V, AC or DC, opto-isolated inputs for your Home or Industrial Automation Projects

This card is replacing the 4-Relays Heavy Duty card by expanding it’s functionality with four truly universal digital inputs, opto-isolated and capable of reading AC and DC signals from 3V to 240V, an RS485 driver, LEDs indicating the status of the relays and inputs, and a push button for resetting or powering down the Raspberry Pi

Perfect add-on to your project when you have to control large number of heavy duty AC loads and/or you have to read wide range inputs. Stackable to 8 layers, the card can add up to 32 relays to each Raspberry Pi in a very compact form factor. In addition, you can read up to 32 opto-isolated inputs.

Pluggable connectors make the 4-RELAYS-4-INPUTS card easy to use when multiple cards are stacked up.  All relays have Normal Open and Normal Close contacts and can switch up to 8A/240VAC. Status LEDs show when relays are on or off. If  you need to switch DC loads of more than 24V, our 8-MOSFETS card can handle up to 240VDC.


The card is compatible with all Raspberry Pi versions from Zero to 4. All stacked cards share the I2C bus using only two of the Raspberry Pi’s GPIO pins to manage all eight cards.  This feature leaves the remaining 24 GPIOs available for the user.


  • Electrical endurance: minim 105 cycles at 1,800 operations per hour, full load
  • Mechanical endurance: minim 107 cycles at 18,000 operations per hour, no load


The 4-RELAYS-4-INPUTS card needs 5V to operate and can be powered from Raspberry Pi or from it’s own pluggable connector. The relay coils are also powered from the 5V.  The card draws 10mA with all relays off. Each relay needs about 80 mA to turn on. If power is applied to the barrel connector, no other power supply is needed for the Raspberry Pi.


You can control the 4-RELAY-PLUS card by writing your program in the language of your choice using the Command Line system, or the Python Driver.  Browser control is very easy using the Node-Red node we provide.


The 4-RELAYS-4-INPUTS card can be tested before installation by running a simple command from the command line. The card will cycle each relay on and off at 0.5 seconds interval. The clacking noise of the relays and the lighting of the LEDs will assure that all relays are functioning.


Up to eight 4-RELAYS-4-INPUTS cards can be stacked on your Raspberry Pi. Each card is identified by jumpers you install to indicate the level in the stack. Cards can be installed in any order. The three position jumper on the upper right corner of the card selects the stack level. For your convenience, two jumpers are provided with each card. For complex Home Automation tasks you can add to the stack one or more Home Automation cards with analog and digital inputs and outputs.


Connect the card to other Industrial Automation systems using RS485/Modbus communication ports. The RS485 can be driven  directly from the Raspberry Pi using the dedicated pins on the GPIO connector, which are routed on the Industrial board to the RS485 driver. A local jumper disables the Receive line if you need to use the GPIO pin for other functions.


User’s Guide and Schematics of the 8-RELAYS card can be downloaded from our website.


Install your Raspberry Pi and up to eight 8-RELAYS cards parallel to the DIN-Rail using our  DIN-RAIL Kit Type-1. Install the whole assembly  perpendicular to the DIN-Rail using the DIN-RAIL Kit Type-2.


  • 4-RELAYS-4-INPUTS add-on card for Raspberry Pi

4 Relays 4 Inputs for Raspberry Pi

  • Mounting hardware
    • Four M2.5x18mm male-female standoffs
    • Four M2.5x5mm screws
    • Four M2.5 nylon nuts

Mounting Hardware

  • Two Jumpers

2 Jumpers

  • Eight 3-pin female mating connector plugs for relays and inputs

4-Relay Connectors

  • Two 2-pin female mating plugs for power and RS485


  1. Plug your 4-RELAYS-4-INPUTS card on top of your Raspberry Pi and power up the system.
  2. Enable I2C communication on Raspberry Pi using raspi-config.
  3. Install the 4-RELAYS-PLUS software from
    1. ~$ git clone
    2. ~$ cd /home/pi/4relplus-rpi
    3. ~/4relay-rpi$ sudo make install
  4. ~/4relay-rpi$ 4relplus

The program will respond with a list of available commands.

Additional information

Weight120 g
Dimensions10 × 7 × 2 cm

4 ea. 10A/240VAC





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8-Layer Stackable Card
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