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Wiring and hardware differences from RAMPS etc

If you are upgrading your 3D printer electronics from RAMPS or similar to Duet WiFi, these are the main hardware differences you need to take account of.

Power ¶ 

The Duet has a single 12V/24V power input, called VIN, for both the bed heater and everything else; whereas RAMPS has two power inputs. If your RAMPS system had a single PSU, you can feed both PSU cables into the single VIN terminal block on the Duet if they will fit, or else run a single heavy-duty cable from the PSU to the Duet.

IMPORTANT! Be sure to connect the power leads to the terminals the right way round. The + and - terminals are marked on the underside of the board. The - terminal is on the side nearest the bed heater terminal block, and the + terminal is the one nearest the stepper motor connectors.

If your RAMPS system has two separate PSUs and you do not wish to use a single PSU instead, then connect the bed heater and its PSU as follows:

  • One bed heater wire to the BED- pin on the Duet bed heater terminal block
  • Other bed heater wire to the +ve output of the bed heater PSU
  • -ve output of the bed heater PSU to the -ve side of the VIN terminal block (marked GND) (the -ve input from the main power supply goes here too).
  • Do not connect the bed heater PSU +ve output to the Duet.

Endstop switch connectors ¶ 

The 3-pin endstop switch connector pinout is different between Duet and RAMPS. If you are using simple microswitches, connect them to the two outer pins of the 3-pin endstop connector. For other types of endstop, see connecting endstop switches and the Duet wiring diagrams. Active endstops must be compatible with 3.3V supply voltage.

The Duet has a single endstop connector for each axis. You configure whether this is a high or a low endstop in firmware.

Stepper motors ¶ 

These are connected in the same way as for RAMPS. However, the two Z motor connectors are typically connected in parallel on RAMPS but in series on Duet WiFi. This gives better performance for the vast majority of stepper motors used in 3D printers, and avoids the need to run the driver at double the current.

As shipped, the Duet WiFi has two jumpers fitted on the ZB connector, to allow operation with a single Z motor. If you have two Z motors, remove these jumpers and connect the second motor to ZB.

Z probe ¶ 

The Duet supports two different classes of Z probe:

  • A probe with an analog output is connected to the connector labelled PROBE. The advantage of these types of probe is that the firmware can slow down the probing speed as the trigger height is approached. The voltage fed into the input pin must not exceed 3.3V.
  • Probes with a digital output are connected may be connected either to the PROBE connector or to the E0 endstop switch input. The pin connections for the E0 switch inputs are not the same as for RAMPS (see earlier), and the voltage fed into the STP input must not exceed 3.3V.

Servo-deployed probes can be used, but the signal level for the servo output signal is 3.3V. If your servo needs a 5V signal, you will have to use an external buffer or level-shifter.

Support for LCD displays ¶ 

The only LCD display currently supported is the PanelDue colour touch screen. However, you can control a Duet or Duet WiFi from any smartphone or tablet using the web interface, and there is an on-board SD card socket. So there is less need for an LCD control panel than with other electronics.

Printer Specific Warnings ¶ 

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