LCD And Keypad for Generation 3

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LCD & Keypad for Generation 3 Electronics

Release status: unknown

LCD (Revar).jpg
Documentation of LCD & Keypad for Generation 3 Electronics
[[LCD+Keypad Control Panel for Makerbot [1]]]
CAD Models
External Link

LCD & Keypad for Generation 3 is an idea from RevarBat on Thingiverse that he implemented for Makerbot using Generation 3 Electronics. This page describes how to do the same thing for a 'Standard' Mendel. Adding the LCD & Keypad with the needed firmware changes allows operating your Mendel without a PC or laptop. The extruder and temperatures can be set and viewed and it is possible to print gcode files directly from the SD card.


The Gen3 Motherboard provides an SD card slot that has never been utilized by the RepRap firmware (the Makerbot firmware uses it to temporarily hold the gcode file to be printed). It would be extremely useful to to be able to load up the SD card with objects that we want to print either as a production machine for creating new Mendels (or Mendel variations) or as a demonstration machine with popular small objects such as the whistle, penny bottle opener, screw box, heart box and etcetera.

However, in order to make use of such a capability one needs some sort of display and input. This article describes how to add a serial LCD and common 16 button keypad to the standard Mendel Generation 3 electronics to provide the capability described above plus constant display of the extruder and bed temperatures (set and current) as well as the capability to set, activate and deactivate the extruder and bed heaters in addition to moving the x, y and z axis, homing the x, y and z axis and zeroing the x, y and z axis.

In short, by making this addition to your Mendel you have a stand alone production/demo machine. It does not need to be connected to a PC and you can print one Mendel set after another or you can take the machine to a meeting w/o having to drag along a laptop and demonstrate the printer by printing out popular objects.

As far as I am concerned this is a must have addition for a RepRap Mendel.


If you are using the Generation 3 electronics directly with a PC power supply (as used by Makerbot) then you do not need to make any changes here...

On/Off Switch

If you are using a simple +12 volt laptop power supply (brick) then you may not have a power switch. Since this is a very useful thing to have we will add it by placing a switch between the power cable and the brick.

Don't use +5 volts from USB

We may no longer use the +5 volts from the USB to power the Motherboard (and SD card) so we must cut this added wire and add a 7805 voltage regulator to generate the +5 volts from our +12 volt power supply.

Step/Dir signals

The Mendel design uses two of the outputs planned for I2C as the STEP and DIR signals to the extruder stepper motor.


Now that the I2C connections are free we can connect the serial LCD to these pins.


The standard Mendel design mounts the Motherboard and Extruder Controller on the thick plate mounted on the top front of the Mendel. This is also a good location for our LCD/Keypad and since we really don't need constant access to the reset button or SD card and since seeing the LCD is more interesting than watching the blinking lights we will simply mount the LCD/Keypad on top of the Motherboard/Extruder controller by using an additional thick plate with appropriate cut outs for the LCD/Keypad.


Of course the firmware must be modified to provide all the nice functionality that we want using the LCD, Keypad and SD card.


  • Move/Jog the extruder position
    • X-axis
    • Y-axis
    • Z-axis
  • Set the temperature
    • Extruder
    • Heated bed
  • Turn heater on/off for
    • Extruder
    • Heated bed.
  • Constantly display status
    • X, Y and Z position
    • Current and set temperatures for
      • Extruder
      • Heated bed
  • Select a gcode file from SD card and print it.

Source Code