4 Relays, 4 Inputs, RS485, 8-Layer Stackable Card for Raspberry Pi – Sequent Microsystems

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Four Relays four HV Inputs
8-Layer Stackable HAT
for Raspberry Pi

Regular price $45.00


  • Four RELAYS with Status LEDs and NO/NC contacts
  • Switch loads of up to 8A and 240VAC/24VDC
  • Four high voltage opto-isolated inputs with status LEDs
  • Separate connectors for low (3V-24V) and high (48-240V) inputs
  • Universal inputs reading AC or DC signals
  • Eight layer stackable to 32 relays and 32 inputs
  • RS485 port
  • Raspberry Pi reset push button
  • Pluggable Connectors 30-16 AWG wires
  • Command Line
  • Python Drivers
  • Node-Red node and examples


Four Heavy Duty Relays plus Four Universal Inputs for Raspberry Pi

Drive 8A/240VAC loads and read 3V to 240V, AC or DC, opto-isolated inputs for all your Home or Industrial Automation Projects

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 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. 

The optically isolated universal inputs can read AC or DC signals from 3V to 48V. The input connectors have a low voltage port which can read signals between 3V and 24V, and a high voltage port which can read signals between 24V and 48V.


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.


The card needs 5V to operate and can be powered from Raspberry Pi or from it's own 2 pin 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 2 pin pluggable connector, no other power supply is needed for the Raspberry Pi.


Up to eight 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. A three position jumper selects the stack level.

Stack Level Jumpers

For your convenience, two jumpers are provided with each card. 


The board is protected to accidental reverse power supply with a 5.8A, 39 mOhm MOSFET which breaks the ground line if reverse power is applied. 


Shutting down the Raspberry Pi by turning off the power can result in SD Card failure. To prevent this, a shutdown command needs to be used before power cut-off. But this requires a monitor, keyboard and mouse connected to the Pi. 

A momentary on push button installed at the edge of the board provides a convenient way to shut down the Raspberry Pi. The button is routed to pin 37 (GPIO 26). You need to write a script which monitors this pin, and if pressed for more than a desired time, issues the shut-down command.


4-RELAYS-4-INPUTS for Raspberry Pi


  • Power Supply: 5V/8A pluggable connector with reverse polarity protection
  • On board resettable fuse: 3A
  • Opto-isolated Digital Inputs:
    • Input Forward Current: Typical 5 mA, maximum 50 mA
    • Low Voltage Input Series Resistor: 2.2K
    • High Voltage Input Series Resistor: 120K
    • Isolation Resistance: Minimum 1012 Ω
  • Relays: NO/NC contacts, 8A/240 VAC-24 VDC


4-Relays 4-Inputs Card Mechanical Specifications





You can write your own application using the Command Line or Python Libraries provided. Usage example for the python library can be found in tests.py file on repository. No programming is required if you use the Node-Red nodes we supply. You can drag-and-drop the functional blocks to design your application. Examples are also provided.


The 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.

RS485/MODBUS port

A standard RS485 transceiver permits the Raspberry Pi to communicate using any protocol including MODBUS, PROFIBUS, camera PTZ control, etc. The transceiver is connected to the serial port of the Raspberry Pi from the GPIO connector, pins 8 (GPIO14, TxD0) and 10 (GPIO15, RxD0). The Rx line is routed through a 2 pin jumper. The jumper needs to be installed in order to use the RS485 port. If the jumper is not installed, both pins can be used as GPIO's



The card can be installed parallel on a DIN-Rail using the DIN-Rail Kit Type 1, or perpendicular using the DIN-Rail Kit Type 2.


When you purchase the Four Relays Card you will receive the following items:

1. 4-RELAYS add-on HAT for Raspberry Pi

    4-RELAYS/4-INPUTS for Raspberry Pi

    2. Mounting hardware

    • Four M2.5x18mm male-female brass standoffs
    • Four M2.5x5mm brass screws
    • Four M2.5 brass nuts
    Mounting Hardware

    3. Two jumpers

    Stack Level Jumpers

    4. Mating connector plugs

    4-RELAYS/4-INPUTS connector plugs


    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 card software from github.com:
    • ~$ git clone https://github.com/SequentMicrosystems/4relind-rpi.git
    • ~$ cd /home/pi/4relind-rpi
    • ~/4relind-rpi$ sudo make install
    • ~/4relind-rpi$ 4relind

    The program will respond with a list of available commands.