The Duet 3 Expansion board 3HC v0.9 3 channel version supports the following:

• 3 high-current stepper drivers
• 3 high current PWM-capable outputs (provisionally 5A each maximum)
• 3 medium current PWM-capable outputs (provisionally 3A each maximum), 2-pin
• 3 outputs for 4-wire fans (separate PWM control wire and tacho)
• 9 low voltage input/output connectors. Some of these have additional facilities, for example UART capability.

Connectivity to the Duet 3 Mainboard is over the CAN-FD Bus.

A 3d render of the board is shown here:

''click on the image for a larger version"

DC42 conducted thermal tests on the drivers running at 4.45A RMS (6.3A Peak) per phase:

This is the FLIR image after 10 minutes, with no fan cooling:

The reported MCU temperature was 62.4C. Adding a quiet 40x20mm Sunon fan brings the temperatures down nicely:

The reported MCU temperature came down to 43C. Ambient temperature during these tests was 27C.