The Duex 2 and Duex 5 are expansion boards for the Duet 2 Wifi and Ethernet. They provide up to 5 additional stepper, heater etc channels to allow for 3d printers or other machines with more axis, multiple drivers per axis, tool changers ets.

In the following instructions given for the Duex 5 apply equally to the Duex 2 except where noted..

The Duex 2 and Duex 5 are based on the same PCB with 3 channels of steppers, heaters fans etc not populated on the Duex 2 to save costs.

• 5 additional TMC2660 stepper motor drivers with stall notification.
• 5 additional extruder heater outputs.
• 5 servo outputs with 5V power and 5V signal levels, sharing control channels with the heaters. So you can use unused heater channels to drive servos.
• 5 additional endstop inputs with indicator LEDs and 3.3V/5V voltage selection. These are also usable as outputs.
• 6 additional PWM controlled fan outputs*, also usable for driving LEDs etc. The output voltage may be switched between 5V, 12V and VIN .
• 4 uncommitted general purpose I/O pins.
• 12V 2A switching regulator, for generating a 12V supply for fans, LEDs etc. when the VIN power is higher than 12V.
• 5 additional thermistor inputs.
• Support for 2 more thermocouple or PT100 daughter boards, supporting up to 4 more sensors.
• Optional 5V external power input for powering servos, fans etc.

• 2 additional TMC2660 stepper motor drivers with stall notification.
• 5 additional extruder heater outputs.
• 5 servo outputs with 5V power and 5V signal levels, sharing control channels with the heaters. So you can use unused heater channels to drive servos.
• 5 additional endstop inputs with indicator LEDs and 3.3V/5V voltage selection. These are also usable as outputs.
• 6 additional PWM controlled fan outputs, also usable for driving LEDs etc. The output voltage may be switched between 5V, 12V and VIN .
• 4 uncommitted general purpose I/O pins.
• 12V switching regulator, for generating a 12V supply for fans, LEDs etc. when the VIN power is higher than 12V.
• 5 additional thermistor inputs.
• Support for 2 more thermocouple or PT100 daughter boards, supporting up to 4 more sensors.
• Optional 5V external power input for powering servos, fans etc.

• 2 additional TMC2660 stepper motor drivers with stall notification.
• 2 additional extruder heater outputs.
• 2 servo outputs with 5V power and 5V signal levels, sharing control channels with the heaters. So you can use unused heater channels to drive servos.
• 2 additional endstop inputs with indicator LEDs and 3.3V/5V voltage selection. These are also usable as outputs.
• 6 additional PWM controlled fan outputs*, also usable for driving LEDs etc. The output voltage may be switched between 5V, 12V and VIN .
• 4 uncommitted general purpose I/O pins.
• 12V switching regulator, for generating a 12V supply for fans, LEDs etc. when the VIN power is higher than 12V.
• 2 additional thermistor inputs.
• Support for 2 more thermocouple or PT100 daughter boards, supporting up to 4 more sensors.
• Optional 5V external power input for powering servos, fans etc.

Note 6 fan outputs were introduced from version 0.8 onwards

The Duex is designed to be mounted back-to-back with the Duet 2 using long M4 screws and spacers. Alternatively, it can be mounted adjacent to the Duet 2 with the expansion connectors on the two boards next to each other.

It is also possible to mount the two boards side-by side with power connectors next to each other, but in this case the 50-way ribbon cable needs to be at least 200mm long instead of the standard 100mm.

As with the Duet 2, the stepper motor drivers are cooled via the PCB. To improve cooling, you can use a fan to blow air over the PCB, especially the underside. When the Duet 2 and Duex are mounted back to back, you can use a single fan to blow air between the two boards.

Note, these expansion boards are not compatible with the Duet 0.6 or 0.8.5

Duex 2 and Duex 5 wiring diagram

• Use the 50-pin ribbon cable supplied with the Duex 5 to connect the two expansion connectors together. Important! The cables must be oriented as shown in the diagram. If you have a white pre-production Duet 2 WiFi then the 50-way expansion connector is probably fitted the wrong way round, with the keyway on the side next to the edge of the board (wrong!) instead of away from the edge (correct). To fit the cable, you will need to file down or cut off the protruding key on the cable end.

• Connect VIN and GND terminals of the Duex 5 to the corresponding terminals of the Duet 2. Do not run separate ground wires from each terminal block back to the power supply unless the power supply is very close (less than 100mm) to the Duet 2 and Duex. Instead, run a very short and thick ground wire directly from the negative (-) terminal of the VIN terminal block on the Duex board to the negative VIN terminal of the Duet. Also connect the negative wire from your power supply to the negative VIN terminal of the Duet. You can run separate +VIN wires from the Duet 2 and Duex back to the positive terminal of the power supply if you wish. The screw terminal rated current is 25A maximum. At high currents, it is essential to use either ferrules or solid core wire with the terminal blocks on the Duet 2 and DueX.
• Caution! On early production (v0.6, v0.7) Duex 2 and Duex boards, the VIN and GND markings on the underside of the board are incorrect and should be swapped over, so GND is the terminal that is also marked -, and VIN is the terminal that is also marked +.
• Important! You must have a reliable low-resistance connection between the negative (ground) terminals of the two VIN terminal blocks. Failure to do so may result in high currents flowing in the ground connectors of the ribbon cable and may cause damage to the Duet 2 or Duex. Preferably, make this connection using either solid core wire, or stranded core wire with ferrules of the correct size crimped on securely. Re-tighten the terminal block screws regularly for the first few days of use, to make sure there is no creep in the wires causing the screws to become loose.
• Important! If you have previously used the Duet with Duex 4 expansion board, note that the VIN terminal block polarity of the Duex 2 or 5 is not the same as on the Duex 4. Instead, the + and - terminals line up between the two boards when the Duet 2 and Duex 5 are positioned back-to-back.
• You do not need to connect anything to the 5V_EXT_POWER connector unless you want to supply external 5V power to power servos and fans.
• As with the Duet 2, you must never connect or disconnect anything (except the USB connector) when the board is powered up. In particular, connecting or disconnecting stepper motors while powered may damage the stepper driver chips.

In some cases, where current draw is particularly high, for example you have a large number of heaters, you may want to connect more than one PSU.

• The grounds of the VIN connectors of the Duet and DueX should be tied together by a short thick wire as usual.
• If you power up the Duet before you power up the DueX, the stepper drivers on the DueX won't get initialised. Ideally power them up at the same time, or the Duex first.
• If the VIN to the DueX goes below the minimum level (about 10V) then the stepper drivers on the DueX will stop functioning, but you won't be warned about it, because VIN to the DueX is not monitored separately.
• It should be possible to use PSUs of different voltages, eg 24V and 12V.
• Another way to use 2 PSUs would be to use one to power the bed heater only and the other to power everything else.

• Place the fan voltage select jumper in the 5V, 12V or VIN position according to your needs
• Place the endstop voltage selection jumper in the 5V or 3.3V position according to your needs
• Place the 5V_SELECT jumper in the INT position, unless you want to provide 5V power to servos and fans from the external 5V input
• If you will be using VIN power greater than 12V and you wish to enable the on-board 12V converter, put a jumper across the 12V_EN PINS

The Duex 2 or 5 is supported in firmware 1.16 and later. You must upgrade your firmware if you are using an earlier version.

• Double check your wiring, in particular the polarity and security of the connections to the VIN terminal block. The Duex is not protected against reverse supply voltage polarity.
• Apply 5V power only, for example via the USB port on the Duet 2.
• Connect to the Duet 2 via Duet Web Control, or using a USB host program such as Pronterface.
• If using DWC, go to the Gcode Console page
• Send command M115. Check that the ELECTRONICS string reports "Duet 2 WiFi + Duex 5" or "Duet 2 WiFi + Duex 2" as appropriate. If the "Duex 5" part is missing, remove power and check your wiring.
• If you have connected additional thermistors, thermocouples or PT100 sensors, send appropriate GCode commands to enable them and test that they are giving the correct readings.
• If everything is working so far, apply 12V or 24V power and proceed with testing other devices you have connected.

From revision v0.10 we stopped producing Duex 2s due to the lack of demand but added the ablity to modify a Duex 5 so that it could be used as a Duex 2. There are two modifications to do, both of which use drillable/solderable jumpers on the Duex5 v0.10 PCB. The first change is to change the board ID so that the Duet 2 thinks a Duex 2 is attached, and the second is to disable the onboard drivers so that external drivers can be used.

There is a jumper marked "Cut for Duex 2" on the underside of the Duex 5 v0.10 board:

To break the circuit to make the Duex 5 appear to be a Duex 2, gently remove the copper ring of the jumper using a 1mm drill bit and confirm its removal by testing between the two pads using a multi-meter; there should be no connection.

''Note that the "cut for Duex0" jumper is not supported in firmware yet'.

From version 0.10 it is possible to disable the internal drivers on the Duex 5 so external drivers can be used.

To do this there are 5 small drill-able solder jumpers on the underside of the board labelled EN5 to EN9. The image below shows jumpers EN5 and EN6:

to disable the internal jumper, gently remove the copper ring of the jumper using a 1mm drill bit and confirm its removal by testing between the two pads using a multi-meter; there should be no connection.

Duex5 and Duex 2 have undergone a number of minor PCB revisions. from the original release (0.6) to the current (0.10). All Duex revisions are compatible with all PCB revisions of the Duet 2 Wifi and Duet 2 Ethernet.

• Added a normally connected solder jumper (drill out to disconnect) to the enable line of each stepper driver. This allows for the onboard drivers to be disabled if required.

Compared to PCB revision v0.9 the following change has been implemented:

* Reduce the I2C pullup resistors from 4k7 to 1k0 to improve I2C communication reliability.

Compared to PCB revision v0.8a the following changes have been implemented:

• Further changes to the layout of the 12V circuit to further reduce EMI.
• Moved the location of the 12V enable jumper.
• Change the layout around the SX1509 to improve assembly..
• Added a Mini blade fuse holder and fuse for V_IN (supplied with a 7.5A fuse).
• Added capacitors on stepper driver outputs to reduce EMI
• Minor routing changes.

Compared to PCB revision v0.8 the following changes have been implemented:

• Changed the layout of the 12V BUCK circuit to further reduce EMI.
• Addition of a 12V output header
• Minor routing changes and modification of capacitor values
• Changed the normal component population to only omit the stepper components on Duex 2.

Compared to PCB revision v0.6 the following changes have been implemented:

• Added an additional fan MOSFET (now 6 fans on the Duex).
• Added flyback diodes on the Fan outputs.
• Minor routing changes.