HALL Current Sensor DAQ 8-Layer Stackable HAT for Raspberry Pi

Brings to Raspberry Pi eight-channel data acquisition from HALL current sensors. Each input signal is processed with rail-to-rail instrumentation amplifiers with 30µV offset, 20pA bias, and 0.01µV/°C drift. Can be used with HALL sensors from 1A to 300A, AC or DC, with 2.5±0.625V or 2.5V±1V outputs. Eight LEDs can be programmed to trigger at a pre-set level of the analog inputs. The real-time clock will keep the time indefinitely during a power failure using a CR2032 battery backup. The hardware watchdog will monitor and power cycle the Raspberry Pi in case of software lockup. TVS diodes on all inputs protect the card from external ESD, and the on-board resettable fuse protects it from accidental shorts.

Communication: Connect the HALL Current Sensor HAT to other Industrial Automation systems using RS485/Modbus communication ports. The RS485 can be driven either from the local Processor implementing the Modbus RTU device or directly from the Raspberry Pi using the dedicated pins on the GPIO connector, which are routed to the RS485 driver. In-and-out connectors simplify daisy-chain wiring to other devices.

Compatibility: The HALL Current Sensor DAQ HAT shares the I2C bus using only two Raspberry Pi’s GPIO pins to manage all eight cards. This feature leaves the remaining 24 GPIOs available for the user. The card is compatible with all Raspberry Pi versions from Zero to 5.

Power Requirements: The HALL Current Sensor DAQ HAT operates with a 5V/5A or 24V/1A external power supply. The HAT supplies 5V and 5A to the Raspberry Pi on the GPIO bus. A local 3.3V regulator powers the rest of the circuitry. The card needs only 50mA to operate.

Pluggable Connectors: All the IOs are connected to heavy-duty (8A), 3.5mm pitch pluggable connectors, which make field wiring very convenient for installation and debugging.

Stacking Multiple Cards: Up to eight cards can be stacked on your Raspberry Pi. The three positions of the configuration DIP Switch, labeled ID0, ID1, and ID2, select the stack level. Cards can be stacked in any order.

Card Layout

Electrical Specifications

• Power supply: 3.5mm Pluggable Connector, 5V/5A or 24V/1A
• Power consumption: 50mA
• On board resettable fuse: 7A
• HALL Sensor Inputs: 2.5±0.625V and 2.5V±1V AC/DC

Mechanical Specifications

Features

• Each input can read HALL Current Sensors from 1A to 300A
• Supports 2.5±0.625V and 2.5V±1V AC/DC HALL Sensors
• Eight Level Stackable
• Pluggable Connectors 26-16 AWG wires
• Eight software-programmable LEDs
• RS485/MODBUS Port
• 5VDC Power Supply also powers the Raspberry Pi
• 24V Power Supply provides up to 5A to the Raspberry Pi
• Real Time Clock with Battery Backup
• On board hardware watchdog
• Resettable fuse
• TVS protection on all inputs
• 32-bit Processor running at 64MHz
• Uses only I2C port (address 0x58 to 0x5f), leaves all GPIO pins available
• Works with any Raspberry Pi from ZERO to 5
• ECCN Code EAR99
• Command line
• Python Library
• Node-Red nodes
• Arduino Library
• Home Assistant Integration
• All mounting hardware included: standoffs, screws and nuts
• Open source hardware

Software

Software Interfaces: You can write your application using the Command Line or Python Libraries. No programming is required if you use the Node-Red nodes provided. You can drag-and-drop the functional blocks to design your application. Examples are provided at GitHub.

Field Calibration: All the analog inputs are calibrated at the factory, but firmware commands permit the user to re-calibrate the board or to calibrate it to better precision. All inputs can be calibrated at two points; select the two points as close as possible to the two ends of the scale. To calibrate the inputs, the user must provide analog signals. (Example: to calibrate 0-10V inputs, the user must provide a 10V adjustable power supply.) The calibration process can be done using the command line interface provided.

Watchdog: The card contains a built-in hardware watchdog that guarantees that your mission-critical project will recover and continue running even if the Raspberry Pi software hangs up. After powering up, the watchdog is disabled and becomes active after it receives the first reset or first period set. The default timeout is 120 seconds. Once activated, if it does not receive a subsequent reset from the Raspberry Pi within 2 minutes, the watchdog cuts the power and restores it after 10 seconds.

Raspberry Pi must issue a reset command on the I2C port before the watchdog’s timer expires. The timer period after power up and the active timer period can be set from the command line. The number of resets is stored in flash and can be accessed or cleared from the command line. The online help function describes all the watchdog commands.

RS485/MODBUS Communication: The Sixteen Analog-Digital Inputs card contains a standard RS485 transceiver, which the local Processor or Raspberry Pi can access. Three bypass DIP switches marked TX and RX allow the desired configuration to be set.

RS-485 Selection: If DIP switches are ON, Raspberry Pi can communicate with any device with an RS485 interface. In this configuration, the card is a passive bridge that implements only the hardware levels required by the RS485 protocol. To use this configuration, you need to tell the local Processor to release control of the RS485 bus:

~$ 16univin [0]  cfg485wr 0 0 0 0 0

If DIP-Switches are OFF, the card can operate as a MODBUS slave and implements the MODBUS RTU protocol. Any MODBUS master can access all the card’s inputs and set all the outputs using standard MODBUS commands. A detailed list of commands implemented and parameter addresses can be found on GitHub:

In both configurations, the local Processor needs to be programmed to release (DIP-switches ON) or control (DIP-switches OFF) the RS485 signals. For further information, see the command-line online help.

Firmware Update: A command can update the card firmware in the field. The update is made with the latest firmware version located on our servers. More instructions about the process can be found on GitHub. Please ensure no process, like Node-Red or Python scripts, tries to access the card during the update process.

Whats Includeed

When you purchase the card, you will receive the following items:

Sixteen Analog-Digital Inputs Card

Mounting hardware

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

All required connector plugs

Quick Start

1. Plug your 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 software from github.com:

git clone https://github.com/SequentMicrosystems/8crt-rpi.git
cd 8crt-rpi/
sudo make install
8crt