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Duet 3 Mainboard 6HC provides the following connectors:

6-way barrier strip: two pins for main VIN and GND; two pins for the VIN and GND supply for the OUT_0 terminals; and positive and negative OUT_0 terminals. OUT_0 is intended to drive a bed heater. The ground side of OUT_0 is switched by the mosfet and the positive side is protected by a 15A fuse.

4-pin JST VH DRIVER_0 thru DRIVER_6: Stepper motor connections. (see note below)

2-pin JST VH OUT_1 thru OUT_3: these are intended for extruder heaters or fans. Maximum recommended current 6A each. If you connect inductive loads to these outputs, you must use external flyback diodes.

4-pin KK connectors with offset spigot OUT_4 thru OUT_6: these are intended for PWM-controllable fans. The connector fits a standard PC-type 4-pin PWM fan. Alternatively, a 2-pin fan may be connected between the V_OULCn pin (+ve) and the OUT_n_NEG pin (-ve). The positive supply to these connectors is the centre pin of the 3-pin jumper block labeled OUT4-OUT6_Select. A jumper in the top position will power them from the fused VIN supply. Alternatively you can connect a 3-terminal buck regulator to the 3-pin jumper block to supply the required voltage to the centre pin.

2-pin KK connectors labelled OUT7 thru OUT9: these are intended for fans. Maximum recommended current 2.5A each. Flyback diodes are built-in to these outputs.

5-pin KK connectors labelled IO_0 thru IO_8: these are for endstop switches, Z probes, filament monitors and other low-voltage I/O functions. Each connector provides both 3.3V and 5V power. The inputs will tolerate up to 30V. The outputs are 3.3V signals levels with 470R series resistors.

Caution! The pinout of the 5-pin connectors is not the same as on the 5-pin Z-probe connector for the Duet Maestro! It has been changed to reduce the risk of shorting +5V to +3.3V.

2 pin KK connected labelled RESET_EXT: for an external normally-open reset switch.

3-pin KK labeled PS_ON: open drain mosfet output for controlling an ATX-style power supply or a SSR. The +5V pin can also be used to provide external 5V power. A small amount of 5V power can be drawn from this pin (through an internal 220 ohm resistor), so that the control terminals of an SSR can be connected directly between the +5V and PS_ON pins. Note: on the v0.5 board this connector is rotated 180 degrees compared to the intended orientation on later version boards.

2-pin KK labelled GND and V+: This is for powering an always-on fan or similar. Caution! On v0.5 boards the GND and V_FUSED legends on the underside of the board are the wrong way round! The ones on the top are correct. Note: on the v0.5 board this connector is rotated 180 degrees compared to the intended orientation on later version boards.

2-pin KK labelled TEMP_0 thru TEMP_3: connections for thermistor or PT1000 sensors.

2-pin KK labelled GND 12V : Always on 12V supply. note that this share power supply with the 12V that can be selected for out4-out6 and out 7-out9 so the total 12V current draw should not exceed 800mA.

3-pin KK labelled Laser/VFD: out9 PWM signal level shifted to 5V to allow for a laser/VFD or hobby servo drive. Note that the out9 control signal is shared between this header and the OUT9 12 pin output. Only use one or the other, not both.

2x5 header: This is for connecting PT100and thermocouple interface boards (the same boards that the Duet 2 series uses).

4-pin DotStar LED strip connector: This is to connect and power DotStar LED strips. In firmware 3.01 there is also experimental support for NeoPixel LED strips. When using NeoPixel, connect the Duet DO pin to Neopixel DI and leave the Duet CLK pin not connected. A maximum of 50 NeoPixel LEDs can be controlled. Caution! The total current draw of the Raspberry Pi (including any attached USB devices), DotStar LEDs and other devices powered from the 5V and 3.3V rails on the Duet must not exceed 3.0A.

6-pin SWD connector: This is for firmware debugging and also provides a backup mechanism to program expansion boards.

Diagnostic LED: this blinks continuously when the main board is running normally, about half a second on and half a second off. The expansion board also has a diagnostic LED. When the expansion board starts up this LED will blank rapidly. If the expansion board is connected to a main board running compatible firmware, the LED on the expansion board will switch to blinking synchronously with the main board LED once time sync has been established across the CAN bus.

• The 4 wire motor and OUT1, OUT2 and OUT3 are JST VH series connectors. They require a minimum of 22AWG wire (20AWG or 0.5mm² recommended. Most NEMA17 size stepper motor wire will will not be thick enough to use in the normal way; but you can double the stripped part of the wire back on itself to bulk it up, and put a small length of heatshrink sleeving over the insulation to bulk up the insulation. You will need a suitable crimping tool for the crimp pins, for example Engineer PA21 (use the 2.2mm jaw opening to crimp the bare wire and the 2.5mm on to crimp the insulation). Alternatively you can solder the wire to the crimp pin
• The default 5V power configuration is Internal-5V-EN jumpered, 5V->SBC jumpered (the Duet is powering the SBC) , SBC->5V not jumpered. If you want the SBC to provide 5V to the Duet then remove the jumper from Internal-5V-EN and place a jumper on SBC-5V (leaving the 5V->SBC jumper in place). NOTE this bypasses the 5V protection and a fault on the SBC may damage the Duet.
• The two banks of Low Current outputs (OUT4-6, OUT7-9) can be separately selected to be powered by either VIN or internal 12V. Total 12V fan current draw must not exceed 800mA.
• The separate OUT0 Power in allows for a different voltage to be supplied for the OUT0 high current output (e.g for a large bed heater) If this is not required VIN power must be applied to both the POWER IN and the OUT0 POWER IN terminals for OUT 0 to be powered.

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Caution! On v0.5 boards the GND and V_FUSED legends on the underside of the board are the wrong way round! The ones in the wiring diagram above are correct. This is the same for the jumper block OUT7 - OUT9 that provides power to these connectors respectively (see below).

Caution! On v0.5 boards, do not connect anything to the OUT pin of the IO_5 connector, because on the prototype boards this pin is used to signal to the Raspberry Pi. The IO_5_OUT pin will be available on later version boards.

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