Connect the terminal block labelled POWER IN to your power supply (minimum 11V, maximum 25V). Make sure the wires you use are of adequate gauge to carry the current to supply the bed heater, extruder heater, stepper motors and electronics.
Caution: be sure to get the polarity right! The board is not protected against reverse polarity. The positive wire from the power supply goes to the terminal marked +. Check the wiring diagram for your board if you're unsure. The polarity (+ and -) is also silk screened onto the board.
If you use stranded core wire, do not tin the ends of the wire, because if you do then the heat generated by the current will cause the solder to flow and the connection will become loose. Preferably, use bootlace ferrules on the end of the wires, as supplied with the Duet 2 Wifi and Ethernet.
Important! Re-tighten the terminal block screws after doing the first few prints, and check that they are still tight occasionally after that. The heat generated by the high current carried by the power wires can cause them to creep and make the connection less tight, especially if you used stranded core wire and no ferrules.
Bed heater power
The Duet boards are designed to power the heated bed (or the solid-state relay controlling it) from the same power supply as they power everything else. The Duet 2 is able to supply 18A to a heated bed (15A on Duet 2 from revision 1.04 on due to the rating of the fuse). If you still want to use a second supply to power the bed (still not exceeding the 18A the Duet can sink), it is possible to arrange this; see Wiring and hardware differences from RAMPS etc for details.
As with the main power wiring, do not tin the wires. Instead it is recommended to use the included bootlace ferrules.
The Duet operates on two power circuits: a 5V circuit that powers the CPU, WiFi, and web interface, (mostly through a 3.3V LDO) and a 12/24V circuit that powers the motors and heaters.
5V power can be supplied in three ways:
- From USB ( whether or not an external power supply is attached). This is normally used for initial setup but is not required for normal operation. Note that USB current is limited by the original USB specification to 500mA. Keep this in mind if you are running a PanelDue, especially the 7Inch version which requires more current than this. Some more modern USB ports and USB hubs will supply more than 500mA.
- From the 12/24V supply through the internal switching regulator. This is the most typical way of providing the 5V supply but it means the board is only powered when VIN is present. The regulator is enabled if the INT 5V_EN jumper is fitted, as shown here:
- Alternatively the board can obtain 5V power from an external 5V supply (for example, the +5VSB rail on an ATX power supply) if you fit the EXT 5V_EN jumper:
If the main PSU supports an ATX-style PS_ON pin (power supply on when pin is connected to ground), the Duet 2 can enable and disable the main power as needed. Obviously this will not work if the only source of 5V is the 12/24V circuit you are switching; you must either supply USB power or use the 5V in pin from a supply that is not shut down when the 12/24V supply is. On an ATX power supply which provides this function.
If you are using an external relay to control mains power to the PSU, you can wire either the +5v or +3.3v (depending on what your relay requires) outputs from the duet in to the positive terminal of the relay, and wire the ground terminal of the relay to the PS_ON output on the duet. If you are using a mechanical relay and it does not include a flyback diode of some sort, you will need to wire one in parallel with the relay signal.
Controlling the external power supply
If you are using the PS_ON pin to turn on and off an external 12/24V supply it can be toggled using the M80 and M81 gcodes:
M80 ; Turns on the ATX power supply M81 ; Turns off the ATX power supply
Note If the M80 command is inserted into the config.g file and +5V VSB ( standby) power is connected, you can not switch off the board by doing a reset, as after reset the config.g is read and the board powered on again. On the web interface there is a button for toggling the external supply:
To display this button select the check box in the user interface settings area.