(under construction)

Description

We needed a CAN-bus connected 16-channel temperature sensing interface for a circuit-board functional test application. Specifically to monitor the MOSFET temperatures in the flyback converters of the OGS battery board with active balancers. Not finding such interface, we started designing a quick design to perform this task. This escalated quickly to a real product design; this CANopen® interface for 16 thermistors.

Note that this device is not particularly intended for high-accuracy applications, mostly because that does not fit the capabilities of low cost NTC thermistor sensors. Instead, the device enables expanding temperature monitoring using low-cost sensors. For example to monitor motors, bearings, cooling systems, etc.

Functionality

  • Measure 16 standard NTC thermistors (typically 10kΩ)
  • Sample rate 100Hz down to 1/60Hz
  • CANopen® fieldbus, measuring devices profile CiA 404
  • Modbus-RTU RS485 fieldbus*
  • Configuration via CANopen, control panel or using PC application via micro-USB port
  • Possibility for custom firmware with specific signal processing functions
16-channel thermistor interface

Network functions (via our gateway)

  • Stream thermal measurements via JSON
  • View temperatures directly via HTML, no cloud needed
  • Logging to micro-SD card
  • Node-ID assigned via serial number
  • Remote configuration & firmware update

Specifications

  • 24-Bit delta-sigma analog digital converter
  • Autoranging excitation source 10µA-1.5mA, max 3.3V
  • OLED display shows temperature readings (°C or °F) and allows for local control, CAN-bus configuration and SDO editing
  • Sensor inputs galvanically isolated from CAN-bus & power (not from each other)
  • CANopen® device profile for measuring devices and closed-loop controllers (CiA 404)
  • Supports LSS node-ID assignment and Fastscan (CiA 305)
  • Supports automatic bit-rate detection between 10kbps and 1Mbps (CiA 801)
  • CAN-FD 'Ready' (no active support for FD datarates yet, but tolerates FD traffic on bus)
  • Up-to-date EDS file generated by and downloadable from the device
  • Supports power management & monitoring features (CiA 302-9 + custom for monitoring of bus voltage, input current, CPU voltage and CPU temperature)
  • Bus powered, operating voltage 9-36VDC, <1W
  • 26-way 0.1" box-header for sensor connections
  • 2-pin 3.81mm terminal + jumper allows for local earthing of thermistor ground, or to divert ground to another earthing point
  • DIN rail enclosure 101x80, width 17.5mm
  • T-Bus CAN-bus connection // 5-pin 3.81mm terminal block
  • 3-pin 3.81mm Modbus/RS485 terminal block*
  • Micro-USB control & bus-powered capability
  • Mating terminal blocks included, including the T-Bus contact block
  • ATEX (IEC 60079) 'ec' & 'ic'

Plug & Play configuration

Plug&play operation

Out of the box, the device is configured as self-starting to switch to OPERATIONAL state autonomously. The node-ID is programmed to 36 and four TPDOs are configured for 1-second timer-based event trigger. This means the device can be used simply by listening to 'raw' CAN-IDs 0x1A4/0x2A4/0x3A4/0x3A4 to receive the periodic readings from the sensors. (Raw meaning without any CANopen stack or functionality on the receiving end.)

  • Automatic switch to NMT state OPERATIONAL
  • Four TPDOs are sent every second:
    • TPDO1 (CAN-ID 0x180+$NODEID) sends 8 bytes containing CH1-CH4 as 16-bit integers
    • TPDO2 (CAN-ID 0x280+$NODEID) sends 8 bytes containing CH5-CH8 as 16-bit integers
    • TPDO3 (CAN-ID 0x380+$NODEID) sends 8 bytes containing CH9-CH12 as 16-bit integers
    • TPDO4 (CAN-ID 0x480+$NODEID) sends 8 bytes containing CH13-CH16 as 16-bit integers

CANopen

ATEX

Availability

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'CANopen' is a registered trademark of CAN in Automation (CiA)
'OGS control' is a registered trademark of Reijneveld Machinebouw B.V.
Modbus-RTU connectivity under development