Use FREE-SHIPPING discount code for all US orders over $15

Eight HV Digital Inputs 8-Layer Stackable HAT for Raspberry Pi

SKU: SM-I-011

Regular price $40.00


  • Eight HV Digital Inputs 8-Layer Stackable HAT for Raspberry Pi
  • Eight layer stackable to 64 inputs
  • Works with any Raspberry Pi from ZERO to 5
  • Eight digital opto-isolated inputs 3V-24V or 48V-240V AC/DC
  • Separate low/high voltage connectors for each input
  • Pluggable Connectors 26-16 AWG wires
  • Status LEDs on all Inputs
  • RS485/MODBUS Port with dual connectors
  • Uses only I2C port, all GPIO pins available
  • ECCN Code EAR99
  • Eight Inputs for Raspberry Pi
  • All mounting hardware included: stand-offs, screws and nuts
  • Open source hardware and schematics
  • Command Line Driver 
  • Python Library
  • Node-Red nodes
  • OpenPLC module


Eight Digital Inputs for Raspberry Pi
Raspberry Pi can read 26 Input signals through the GPIO header, but sometimes you might need to read more. Since all GPIO pins are wired directly to the local processor, some hardware is required to connect them to the real world.
The card has eight optically isolated digital inputs. Separate input pins are provided for low or high voltage ranges. Inputs can read both DC and AC signals. The card communicates with Raspberry Pi using only the I2C port, leaving all the other 24 GPIO pins available for your use. It has also an RS-485 port, a power LED and a push button that can be used to shut down the Raspberry Pi.
Pluggable connectors make the 8-INPUTS card easy to use when multiple cards are stacked up.

The card is compatible with all Raspberry Pi versions from Zero to 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.

The card needs 5V to operate and can be powered from Raspberry Pi or from it's own 2 pin pluggable connector. The card draws 10mA.  If power is applied to the 2 pin pluggable connector, no other power supply is needed for the Raspberry Pi.


A power LED shows when power is applied to the board. One LED for each input shows when the input is activated.


A six position DIP switch is used to activate the RS485 port and to select the position of the card in the stack, if multiple cards are used.

Eight HV Inputs for Raspberry Pi DIP Switch selection

Up to eight cards can be stacked on your Raspberry Pi. The three bottom positions of the DIP Switch are used to select the stack level.
Eight HV Inputs for Raspberry Pi Stack Level


The 16 Solid State Relay Card has an RS485 port which can be driven from the Raspberry Pi. Set both to ON to connect the RS485 port to USART1 of the Raspberry Pi.

When DIP Switches are ON, Raspberry Pi can communicate with any device with an RS485 interface. In this configuration the card is a passive bridge which implements only the hardware levels required by the RS485 protocol.

When DIP Switches are OFF, the Raspberry Pi GPIO pins can be used for other functions. If multiple cards are stacked, only one card can have the DIP Switches ON.


The first position on the DIP switch is the RS485 line terminator. Set it to ON if the card is last on the RS485 chain.


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.

Eight HV 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




You can write your own application using the Command Line or Python Library 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 provided at GitHub.


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. Shown here is a perpendicular installation which can be expanded to 8 cards.


When you purchase the 16 Universal Inputs Card you will receive the following items:
1. Eight HV INPUTS card for Raspberry Pi
Eight HV Inputs for Raspberry Pi

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

4. Connector Plugs
Eight HV Inputs for Raspberry Pi - connector plugs


  1. Plug your 8-INPUTS card on top of your Raspberry Pi and power up the system.
  2. Enable I2C communication on Raspberry Pi using raspi-config, instructions here.
  3. Install the card software from
  • ~$ git clone
  • ~$ cd /home/pi/8inputs-rpi
  • ~/8inputs-rpi$ sudo make install
  • ~/8inputs-rpi$ 8inputs -h
    The program will respond with a list of available commands.

Customer Reviews

Based on 2 reviews
Reading digital inputs ? Look no further

Investigated a multitude of different options to read digital input signals until I discovered Sequent Microsystems HATs. This was the most practical and easiest solution out there, and as a plus supports a wide range of input voltages all the while optically isolating each input.

Using 3 of these together with / in the following order:
- 1x Waveshare SIM7600G-H LTE HAT
- 3x SM HV digital input HAT
- 1x SM 8-relay 4A/120V HAT
- Raspberry Pi 5 + Raspberry Pi 5 active cooler + RTC battery
- 1x Pimoroni NVMe HAT

Used to monitor (ON/OFF) reed contacts (5v) / motion sensors (12v) in parallel of an analog alarm system, and to arm / disarm the alarm system using SMS + OTP.

Sequent Microsystems is my new first choice for Raspberry Pi HATs.

Wayne Mathis
Excellent solution for reading wide range of signals

This card can read any input from 3V up to 240V. Separate connectors for low or high voltage. All inputs are optoisolated. Super

Notify Me When Available

Fill in the required details to get notified when the product is again in stock!