The Duet range of machine controllers support one or more temperature daughterboards which provide expanded temperature sensor connectivity using Maxim integrated ICs. These daughterboards connect to the Duet digitally over SPI.
Each daughterboard supports 2 channels, ie two thermocouples per daughterboard. Duet mainboards and exapansion boards support none, one or two daughterboards. Refer to the table below.
|Duet board||Number of boards supported|
|Duet 3 Mainboard 6HC||2, stacked|
|Duet 3 Mini 5+||1|
|Duet 3 Expansion 3HC||2, stacked|
|Duet 3 Toolboard 1LC||0|
|Duet 3 Expansion 1XD||0|
|Duet 2 WiFi / Ethernet||2, stacked|
|DueX2 / DueX5||2, stacked|
|Duet 2 Maestro||1|
Boards that support only one daughterboard can have either a Thermocouple or PT100 temperature sensor daughterboard connected, but not both.
The PT100 daughterboard uses the Maxim Integrated MAX31865 RTD sensor IC. This IC supports 2,3 or 4 wire PT100 connections. The mode can be set using jumpers on the board. With the jumpers on/bridged the board expects a 2 wire PT100 sensor. With the jumpers off/cut a 4 wire PT100 sensor can be used. The change between older versions and 1.1 was to move from solder jumpers to pin jumpers.
An external resistor sets the sensitivity for the RTD being used (in the case of the Duet3D daughterboard this is a PT100) and a precision delta-sigma ADC converts the ratio of the RTD resistance to the reference resistance into digital form. High Accuracy: 15-Bit ADC Resolution; Nominal Temperature Resolution 0.03125°C (Varies Due to RTD Nonlinearity). Total Accuracy Over All Operating Conditions: 0.5°C (0.05% of Full Scale) max. For more information see the Maxim Integrated MAX31865 product page.
The STEP file for the Duet3D PT100 temperature sensor daughterboard is shared on the Duet3D github here.
For setting up the Duet us use PT100 sensors see Connecting PT100 temperature sensors
The Duet range of machine controllers support various other temperature sensors. See:
The following minor changes from v1.1 to 1.1a:
From version 1.1 onwards there are two pin jumpers per input channel.
Versions of the board before v1.1 had solder jumpers to convert from 2 wire to 4 wire.