Dual USB 5V DC for MK4S with NFC Reader

Replaces MK4/MK4S power supply cover to provide two 5V USB outputs for powering cameras, LEDs, fans, accessories, etc.
1h 57m
1× print file
0.20 mm
0.40 mm
27.00 g
72
43
2
926
updated January 16, 2025

Description

PDF

This upgrade was designed to provide a DC-DC converter and 5V USB connector to power my Buddy3D camera, with a second USB output to make it easier to power LEDs, ventilation fans, or custom boards connected to the GPIO option for the MK4S.  This cover will also fit the MK4 (which does not have the NFC antenna).

The model consists of three pieces:

  1. The main cover, modified relative to the original Prusa cover to provide mounting features for the components, additional space for the converter wires to come out, and text on the front surface.
  2. A shelf for one end of the converter.  Separating the shelf from the main cover allows the design to be printed without supports.  The shelf has an offset screw hole and beveled interface surface so that it can only attach to the main cover one way, and self-centers when the screw is tightened.
  3. A spacer that holds the two USB boards at the proper spacing.  It also has a tab on one end that is held down by one end of the converter, which helps hold the USB boards in place and reduces stress on the entire assembly when USB cables are inserted or removed.

Design Features:

  • No supports required 
  • Replaces original power supply cover (el-box-cover_R4)
  • Accommodates the NFC antenna for the MK4S.

Parts Required:

Printing Notes:

  • Print with 0.2mm layer height, 3-4 perimeters, 15% infill.  I used 4 perimeters.
  • Supports are not required for any of the parts.
  • Use a material that can withstand higher temperatures.  PETG will work as long as you are not printing high temperature filaments in the enclosure.  I have printed several of these in both PETG-CF and PC-CF, and both materials print well.  PLA is not recommended.
  • Please DO NOT use the .bgcode file that has been provided (always slice your own files for your specific printer, filament, environment, etc.).  The file uses customized profiles, and was only included to provide a reference for approximate print time.

Assembly Instructions (refer to photos):

Step 1:  Insert the two M3 square nuts (one in the main cover, and one in the shelf).

Step 2:  Attach the shelf to the main cover using one M3x10mm button head screw.  Note the orientation of the shelf in the photo (square nut facing the middle of the cover assembly).  The screw is self-tapping; do not over-tighten.  Tighten the screw until the shelf is fully seated and does not move.

Step 3:  Insert the two M3 nuts into the main cover.

Step 4:  Cut the 5V output wires to an overall length of 70mm, then strip 15mm of insulation from the end of each wire.  Tin the wire ends to prevent the strands from fraying when inserted into the USB boards (it makes assembling the boards much easier).

Step 5:  Cut the input wires to a length of 55mm, strip 8mm of insulation from the end of each wire.  Fold each stripped end in half, insert into a ring terminal, and crimp the ring terminal onto the wire.

Step 6:  As shown in the following photo, temporarily assemble the two USB boards and the spacer by inserting the two M3x20mm screws; this holds the two boards at the proper distance while soldering the wires.  Then solder the two wires to each board (four solder connections) and trim the leads flush (including the tabs on the USB connector).

Step 7:  Remove the M3x20mm screws from the spacer/USB board assembly to allow the parts to move more independently, then push the connectors and spacer into cover until they are in position.  Finally, re-insert the two M3x20mm screws and tighten them.

Step 8:  If you are installing this on an MK4S, now is a good time to attach the NFC antenna to the cover…before installing the DC-DC converter (don’t ask me how I know that).

Step 9:  Attach the DC-DC converter using one M3x10mm button head screw and one M3x16mm socket head screw.  The reason for using a button head screw on the left side is that the head needs a lower height to prevent interference with the Ethernet connector on the controller board.

Step 10:  Attach the DC-DC converter input wire ring terminals to the power input connectors used for the heater (stacked on top of the existing ring terminals).  It helps to rotate the ring terminals from the main power supply 180 degrees to minimize interference with the DC-DC converter ring terminals.

Step 11:  If you are installing this on a MK4S, connect the NFC antenna cable following the  assembly manual instructions from Prusa.  

Step 12:  Attach the cover with the two M3x10mm screws that were used for the original cover.

 

Tags



Model origin

The author remixed this model.

Differences of the remix compared to the original

Added a DC-DC converter and two USB connectors to the “el-box-cover_R4” model.

License