Prusa i3 Rework Electronics and wiring

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Introduction | Bill of materials | Y-axis assembly | X-axis assembly | Connecting X-axis and Z-axis | Motor assembly

X and Y-axis motions | Heated bed assembly | Extruder assembly | Electronics and wiring | Marlin Firmware

Mounting electronics

Needed parts

  • Arduino Mega 2650
  • 4x stepsticks
  • 3x Arduino washer
  • 3x M3x24 mm screw
  • 3x M3 nut
  • 3x Ø3 mm washer

Step 1

Mount the RAMPS on the Arduino Mega 2560. You may have to cut the solder joints located below the RAMPS power supply plug. You should have both power supply plugs on the same side.

Step 2

Before plugging in the stepsticks, place three jumpers under where each stepstick goes. This will tell RAMPS to use the highest level of micro-stepping that is supported. Plug each stepstick on the RAMPS according to the illustration below. If you are not using a dual extruder, you will likely have an empty socket. Note also that the stepper coils are numbered 1 and 2, with 1A and 1B going to one coil, and 2A and 2B going to the second coil.

Connecting stepsticks to the RAMPS.
A4988 diagram for direction indication.

Step 3

Fix the electronics assembly to the rear of the aluminum plate with three Arduino washers used to electrically insulate it. Power supply plugs are oriented UPWARD (original wiki entry here said downward but the hole orientation of the real Prusa I3 will not allow that). Use three M3x24 mm screws, three Ø3 mm washers (on the RAMPS) and three M3 nuts.

Electronics holes.


All electrical connections are summarized on the following scheme : LIEN PAGE REPRAP

Note : The second extruder may be replace by a fan to cool the print.

RAMPS wiring sheme.

Endstop wiring

Plug the three endstops to the RAMPS with three connecting wires (wires with an « Endstop » mark) according to the following wiring scheme. This scheme shows the connection for X, Y, and Z min stops. If you have a Y max stop for instance, then you would need to move the Y connection over one.  :

Schéma de branchement des endstops sur le RAMPS.

Motors wiring

You have to connect both Z-axis NEMA 17 motors to work in parallel. To do that, weld both power supply wires (cut in a previous step) according to their colors : red/red, green/green, blue/blue and black/black. We strongly recommend you to protect each weld with heat shrink tubing or an insulating adhesive tape. Note: the RAMPS 1.4 allows you to plug in two Z-axis motors, so cutting/welding of the wires might not be needed.

NEMA 17 wires color can change depending on the supplier and there is no risk in case of a wrong wiring. Indeed, the wires are always associated in pairs (one pair for each coil). SO there is no risk if the color of supply wires doesn’t match the wiring diagram.

Hot End resistor and PCB heatbed wiring

The Hot End (or extruder) resistor is not polarized and is plugged to D10.

PCB heatbed is plugged to D08. Make sure to not invert the positive and negative poles.

Thermistors wiring

The thermistor is not polarized. So you can connect the PCB heatbed thermistor and the Extruder thermistor in both ways.

Fans wiring

Plug the extruder fan directly to its dedicated power supply pins (see illustration below).

If you have a fan which cools the electronics then plug it directly to the RAMPS.

If you have a fan which cools the print then plug it to D9.

Wiring scheme for fans.

Power supply wiring

The main power supply wire is not included. You have to strip an end of a power cable and to connect to the power supply (L, N, G plugs). Make sure to do this operation properly.

The power supply is connected to the RAMPS with additional connecting wires. You have to strip both ends, make sure to follow the scheme correctly.

Check the power supply for 110volt vs 220volt operation.

Power supply wiring.