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.
There have been two versions of the thermocouple board.
|Board revision||Sensor IC||Supported thermocouples|
|v1.1||MAX31856||2 x thermocouples of type B, E, J, K, N, R, S or T|
|v1.0 and earlier||MAX31855||2 x thermocouples of type K|
The MAX31856 performs cold-junction compensation and digitizes the signal from any type of thermocouple. The output data is formatted in degrees Celsius. This converter resolves temperatures to 0.0078125°C, allows readings as high as +1800°C and as low as -210°C (depending on thermocouple type), and exhibits thermocouple voltage measurement accuracy of ±0.15%. See the Maxim integrated website for more details on the MAX31856.
The STEP file for the Duet3D Thermocouple daughterboard is shared on the Duet3D github here.
For setting up Duet controllers to use thermocouple sensors see: Connecting thermocouples
The Duet range of machine controllers support various other temperature sensors. See: