6 RTD Inputs 3-wire PT100/PT1000 for Raspberry Pi I/O Back Panel

Add 6 RTD Inputs 3-wire PT100/PT1000 to your Raspberry Pi Back Panel system for precise, reliable temperature monitoring. The card features true 3-wire compensation, stable excitation, and noise-filtered measurements, with all connections routed cleanly through the Back Panel. Control it via CLI/Python or RS485/MODBUS, and scale by stacking alongside other HOP modules. FEATURES Six RTD inputs, 3-wire compensation - supports PT100 and PT1000 probes True 3-wire lead compensation per channel to minimize cable resistance error Precision excitation and low-noise front end for stable, repeatable readings Mains-hum rejection (50/60 Hz) and input filtering for noisy environments Back Panel integration - clean wiring via Back Panel terminals; auto slot addressing RS485 / MODBUS RTU support for use with external PLCs (no Pi required) CAN Support via CANopen Integrated CAN interface enables reliable CANopen communication for seamless industrial networking and real-time device control. I²C control from Raspberry Pi with command-line tools and Python/C libraries OpenPLC and CODESYS integration options for industrial workflows LED status per channel and system indicators for quick diagnostics Stacks with other HOP cards - mix up to 8 cards per Back Panel; chain panels for larger systems Powered via Back Panel; no extra supply or cabling required for the card itself Built-in OLED Display:128×32 dot matrix screen for displaying system status, messages, or sensor values. DESCRIPTION Part of the HOP (Hardware On Panel) family developed by Sequent Microsystems, the card is designed to integrate seamlessly with the Raspberry Pi Back Panel. Up to eight HOP cards—of any type—can be installed on a single Back Panel, offering maximum flexibility for industrial automation applications. Multiple Back Panels can be connected horizontally to support larger projects. Each input can be configured in software to read either PT100 or PT1000 probes - no jumpers or DIP switches required. Like all HOP cards, the 6 RTD Inputs 3-wire PT100/PT1000 Card features 18 LED indicators. The power LED blinks when power is applied and the local processor is operational. An error LED illuminates when an input is outside a predefined condition. Sixteen additional LEDs display the real-time status of each input, also indicating whether the input is in PT100 or PT1000 mode. An RS485 port enables communication with external PLCs or industrial controllers using the industry-standard MODBUS RTU protocol. Power Requirements The Card is powered via the Back Panel power connector. The local processor is powered from the 5V rail through a 3.3V LDO regulator and consumes 10 mA. WATCHDOG: If the watchdog is enabled and the Raspberry Pi fails to access the 6 RTD Inputs 3-wire PT100/PT1000 Card within the preset time, the card signals the Back Panel, which performs a hard reset of the Raspberry Pi by turning the power off for 10 seconds. STACK LEVEL: The stack level is automatically determined by the slot into which the card is inserted on the Back Panel. It is shown on the OLED display after power up. Up to eight cards of the same type can be connected to a single Back Panel installation. INTERRUPT: Any HOP card can be programmed to interrupt the Raspberry Pi. The interrupt handler running on Raspberry Pi needs to monitor pin 37 on the GPIO interface. BACK PANEL TERMINAL BLOCK PINOUT Each slot on the Back Panel has alocated three 6-pin spring-loaded terminal blocks for IO wiring. The pinout is shown in the following picture: Six RTD Inputs: Each input has three terminals, labeled Tx1, Tx2 and Tx3. Connect the PT100/PT1000 probe between Tx1 ans Tx2, and the compensating wire to Tx3. Short Tx2 and Tx3 to use 2 wire probes. IO01: T11 IO07: T31 IO13: T51 IO02: T12 IO08: T32 IO14: T52 IO03: T13 IO09: T33 IO15: T53 IO04: T21 IO10: T41 IO16: T61 IO05: T22 IO11: T42 IO17: T62 IO06: T23 IO12: T43 IO18: T63 DOT MATRIX DISPLAY The 6 RTD Inputs 3-wire PT100/PT1000 Card includes a 128 × 32 dot-matrix display driven by the on-board processor. It can show status information, self-test results, and error messages. At power up it displays the card name and the I2C address. ELECTRICAL SPECIFICATIONS Power Supply: 5V 10mA Back Panel provided MECHANICAL SPECIFICATIONS DOWNLOADS Hardware Schematic V1.0 2D DXF Mechanical 3D STEP Model 3D Printable Enclosure SOFTWARE Command Line Drivers Python Libraries CODESYS Driver OpenPLC Module QUICK START Plug the 6 RTD Inputs 3-wire PT100/PT1000 Card on the Back Panel for Raspberry Pi and power up the system. Enable I2C communication on Raspberry Pi using raspi-config. Install the software from github.com: git clone https://github.com/SequentMicrosystems/sequent-cli.git cd /home/pi/sequent-cli sudo make install sequent-cli 6rtd -h The program will respond with a list of available commands. FAQ Q: What is the function of this card? A: It provides six programmable RTD Inputs, each configurable to read PT100 or PT1000 probes, for industrial control applications. Q: Can I mix this card with other HOP cards on the same Back Panel? A: Yes, up to eight HOP cards of any type can be installed on a single Back Panel, allowing flexible I/O combinations. Q: How do I configure PT100 or PT1000 probes? A: Output mode is configured in software—no need for jumpers or DIP switches. Q: What software platforms are supported? A: The Card supports MODBUS RTU over RS485, and is compatible with OpenPLC, CODESYS, and Sequent’s command-line utilities. Q: What do the LEDs indicate? A: One LED indicates power and processor health, one signals an error condition, and 12 LEDs display real-time input activity and mode. Q: How is the card powered? A: Power is supplied through the 5V rail of the Raspberry Pi Back Panel. Q: Is this card stackable? A: Yes. It can be stacked with up to seven other HOP cards per Back Panel. Additional Back Panels can be chained for larger systems. Q: Can I use this card without a Raspberry Pi? A: Yes, via RS485 and MODBUS RTU, the card can be controlled by an external PLC or industrial controller without a Raspberry Pi. Q: What types of loads can the outputs drive? A: The card is designed to drive standard industrial 4–20mA current loops in both sourcing and sinking configurations. Refer to the datasheet for load specifications.