Four Smart Relays with Universal Inputs 8-Layer Stackable HAT for Raspberry Pi

The Sequent Smart Relays HAT for Raspberry Pi features four relays with HALL sensors, current limiting, 10A switching, universal inputs, RS485/MODBUS, PWM and encoder support, a reset button, and GPIO-friendly stacking. Includes pluggable connectors, power loss protection, and Home Assistant integration.

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The Smart Relays HAT for Raspberry Pi is an ideal solution for mission-critical projects where you have to be 100% sure that your system works as expected. HALL effect sensors on relay outputs monitor the load current in real time. Not only can you be sure that your loads operate within specified parameters, but you can also measure the load power, and you can limit the load current to any value from 1 to 10A.

The HAT’s universal inputs can read temperatures from 10K thermistors, dry contact or opto-isolated 0-24V signals. Stackable to 8 layers, the Smart Relays HAT can add up to 32 relays and 32 analog/digital inputs to each Raspberry Pi in a very compact form factor.

Pluggable connectors make the card easy to use when multiple cards are stacked up. All relays have Normal Open and Normal Close contacts and can switch up to 10A/240VAC.

Raspberry Pi not included

Compatibility

The Smart Relays card is compatible with all 40-pin Raspberry Pi models from Zero to 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.

Power requirements

The card operates from a 5V or 10-24V power supply. In both cases, it provides 5V and up to 5A to the Raspberry Pi. The relay coils are also powered from 5V. The card draws less than 50mA with all relays off. Each relay needs about 80 mA to turn on.

Stacking multiple cards

Up to eight cards can be stacked on your Raspberry Pi. Three positions of the configuration DIP switch labelled ID0, ID1, ID2 are used to select the stack level. Cards can be stacked in any order.

Reset pushbutton

Shutting down the Raspberry Pi by turning off the power can result in MicroSD 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 read by the local processor, which can be programmed to signal the Raspberry Pi by setting low pin 37 of the Raspberry Pi GPIO connector (GPIO26). You can also read the status of the pushbutton from the I2C interface. You need to write a script which monitors this pin, and if pressed for more than a desired time, issues the shut-down command.

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 clacking noise of the relays and the lighting of the LEDs will assure that all relays are functioning.

RS-485/MODBUS port

A standard RS-485 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. Install the jumpers 485-TX and 485-RX on connector J3 to drive the port from Raspberry Pi. Install the terminator jumper 485-TERM if the card is last on the RS-485 chain.

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

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 interfaces

You can write your own application using the command line or Python libraries provided. 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.

Features

• Four relays with HALL effect sensors on loads
• Switch and measure AC/DC currents up to 10A
• Monitor load failure, compute load power, limit load current
• Four analog inputs reading temperature from 10K thermistors
• Four digital inputs reading dry contact or 24V opto-isolated signals
• 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
• Enhanced 24V power supply delivering up to 5A at 5V to Raspberry Pi
• Switch loads of 10A and 250V on all four outputs
• Hardware watchdog power cycles the Pi on software lockup
• NO and NC contacts on all relays
• Status LEDs on inputs and outputs
• Switch loads of up to 10A and 240VAC/24VDC
• Eight layer stackable to 32 relays and 32 inputs
• RS485/MODBUS port
• Raspberry Pi reset push button
• Pluggable connectors 30–16 AWG wires
• Uses only I2C port (address 0x15..0x0e), all GPIO pins available
• Works with any Raspberry Pi from Zero to 5
• ECCN code EAR99
• Command Line
• Python Drivers
• Node-Red Nodes
• OpenPLC module
• Arduino Library
• HomeAssistant Integration

Electrical specifications

• 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

Resources

• Smart Relays Downloads

Package Contents

• 1x Four Smart Relays with Universal Inputs 8-Layer Stackable HAT for Raspberry Pi
• 4x M2.5x18mm male-female brass standoffs
• 4x M2.5x5mm brass screws
• 4x M2.5 brass nuts
• 10x Mating connector plugs

Raspberry Pi not included