Four Relays Four Inputs 8-Layer Stackable Card for Raspberry Pi (v5.0)

Four heavy-duty relays plus four universal inputs for your Raspberry Pi - and now with a custom Home Assistant integration!

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

A perfect add-on to your project when you have to control a 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 this 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 240V. The input connectors have a low voltage port that can read signals between 3V and 24V, and a high voltage port that can read signals between 48V and 240V.

For any technical questions about this product please email support@sequentmicrosystems.com

New!

The latest versions of the card replaced the I/O expander with a local processor. This enhancement allowed us to add several new features:

• Independent RS485 (no Raspberry Pi needed)
• MODBUS protocol allows the card to be controlled from any PLC
• Transition counters to 4kHz on all inputs
• Input counters with cumulative or PPS (pulse per second) reading up to 4kHz
• 2 x Quadrature encoder inputs reading up to 4000 PPS
• PWM inputs on each channel, reading both the fill factor and the frequency

Features

• Four RELAYS with Status LEDs and NO/NC contacts
• Four universal opto-isolated inputs with status LEDs
• Eight layers stackable to 32 relays and 32 inputs
• RS485/MODBUS transceiver
• MODBUS protocol allows the card to be controlled from any PLC
• Independent RS485 (no Raspberry Pi needed)
• Input counters with cumulative or PPS (pulse per second) reading up to 4kHz
• PWM inputs on each channel, reading both the fill factor and the frequency
• Raspberry Pi reset push button
• Pluggable Connectors 30-16 AWG wires
• Switch loads of up to 8A and 240VAC/24VDC
• Read 3V to 240V AC/DC inputs
• Software self-test
• Command Line
• Python Drivers
• Node-Red node and examples
• OpenPLC module
• Arduino Library
• Home Assistant Integration
  

Feature Details

Power Requirements

The card needs 5V to operate and can be powered from Raspberry Pi or from its 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.

Stacking Multiple Cards

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

Reverse Power Supply Protection

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

Reset Pushbutton

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 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 that monitors this pin, and if pressed for more than the desired time, issues the shut-down command.

Compatibility

The card is compatible with all 40-pin Raspberry Pi versions from the Pi Zero to the Raspberry Pi 5. 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.

DIN Rail Mounting

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.

Software

Software Interfaces

You can write your own application using the Command Line or Python Libraries provided. A usage example for the python library can be found in the tests.py file in the 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.

All downloads can be found here.

Relay Self Test

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 second intervals. The clicking 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 can be driven either from the Raspberry Pi serial port or directly from the local processor.

Extended functions of the input ports

• Transition counters to 4kHz on all inputs
• Input counters with cumulative or PPS (pulse per second) reading up to 4kHz
• 2 x Quadrature encoder inputs reading up to 4000 PPS
• PWM inputs on each channel, reading both the fill factor and the frequency
• 1% resolution on PWM inputs up to 100Hz, 5% resolution up to 500Hz.

Quick Start

• Plug your 4-RELAYS/4-INPUTS card on top of your Raspberry Pi and power up the system.
• Enable I2C communication on Raspberry Pi using raspi-config.
• 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.

Package Contents

• 1x 4-relays Add-on Card For Raspberry Pi
• 1x Mounting hardware pack
• 1x Pluggable connector pack

Raspberry Pi not included

Electrical Specification

• Power Supply: 5V/8A pluggable connector with reverse polarity protection
• Onboard resettable fuse: 3A
• Opto-isolated Digital Inputs:
• Input Forward Current: Typical 5 mA, maximum 50 mA
• Low Voltage Input Series Resistor: 1.2K
• High Voltage Input Series Resistor: 10K
• Isolation Resistance: Minimum 1012 Ω
• Relays: NO/NC contacts, 8A/240 VAC-24 VDC

Revision History

• As of 16/01/2025 we are now stocking V5.0