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Arduino Mega Pololu Shield – RAMPS information & schematic

RepRap Arduino Mega Pololu Shield, or RAMPS for short. It is designed to fit the entire electronics needed for a RepRap in one small package for low cost. RAMPS interfaces an Arduino Mega with the powerful Arduino MEGA platform and has plenty room for expansion. The modular design includes plug in stepper drivers and extruder control electronics on an Arduino MEGA shield for easy service, part replacement, upgrade-ability and expansion. Additionally, a number of Arduino expansion boards can be added to the system as long as the main RAMPS board is kept to the top of the stack.

Contents

Introduction

Version 1.4 uses surface mount capacitors and resistors to further cover edge issue cases. As of version 1.3 in order to fit more stuff RAMPS is no longer designed for easy circuit home etching. If you want to etch your own PCB either get version 1.25 or Generation 7 Electronics. Version 1.25 and earlier are “1.5 layer” designed boards (i.e. it’s double sided board, but one of layers can easily be replaced with wire-jumpers) that is printable on your RepRap with the etch resist pen method, or home fabbed with toner transfer.

This board is mostly based on Adrian’s Pololu_Electronics and work by Tonok. Copper etch resists methods suggested by Vik. Also inspired by Vik’s work with EasyDrivers. Circuit design based mostly on Adrian’s Pololu_Electronics. Joaz at RepRapSource.com supplied initial pin definitions and many design improvements. Much inspiration, suggestions, and ideas from Prusajr, Kliment, Maxbots, Rick, and many others in the RepRap community.

  • Mendel printed RAMPS wired to Mendel.

  • Mendel with RAMPS in enclosure mounted.

  • screen capture of 2-sided RAMPS layout

  • commercially fabbed 2-sided RAMPS wired to Mendel

Features

  • It has provisions for the cartesian robot and extruder.
  • Expandable to control other accessories.
  • 3 mosfets for heater / fan outputs and 3 thermistor circuits.
  • Fused at 5A for additional safety and component protection
  • Heated bed control with additional 11A fuse
  • Fits 5 Pololu stepper driver board
  • Pololu boards are on pin header sockets so they can be replaced easily or removed for use in future designs.
  • I2C and SPI pins left available for future expansion.
  • All the Mosfets are hooked into PWM pins for versatility.
  • Servo style connectors are used to connect to the endstops, motors, and leds. These connectors are gold plated, rated for 3A, very compact, and globally available.
  • USB type B receptacle
  • SD Card add on available — Available now made by Kliment – Sdramps
  • LEDs indicate when heater outputs on
  • Option to connect 2 motors to Z for Prusa Mendel

 

 

 

Safety Tip

Generation3Electronics-achtung.gif

Once you start putting electricity into your RepRap – even at just 12 volts – you have to take basic, common sense precautions to avoid fires. Just in case these fail, test your workshopsmoke detector. Don’t have a smoke detector? Get one!

Schematic

Current schematic shown. For older versions click the image. Click again for full image. This is the schematic of the shield.

Change Log

  • 1.4 August 4, 2011
  1. Changed capacitors and resistors to surface mount components
  2. Added LEDs to mosfet outputs
  3. Added bulk capacitors for each stepper driver
  4. Added pull up resistors to enable to override the Pololu drivers default enabled state
  5. Added mosfet gate resistors
  6. Added pull-ups for I2C
  7. Servo1 connector moved to pin 11 to free 7 for ADK
  8. Fixed thermals
  9. Servo 5V supply is only connected to VCC if a jumper is added
  10. Reset switch changed for small footprint
  11. Moved Aux conectors around a bit and increased board size ~0.1″
  12. Added some space around Q3 for a small heatsink
  • 1.3 May 13, 2011
  1. Added 5th stepper driver socket
  2. Added 3rd thermistor circuit
  3. Added Heated bed circuit w/ 11A PTC fuse, changed to 4 position pluggable input jack to accommodate additional current
  4. Increased board size to 4″x2.32″
  5. Pin order on heater outputs changed
  6. Increased spacing increased to accommodate different connectors
  7. Added connectors for optional 2 motors on Z driver
  8. Added connector for PS control
  9. Improved expansion connector layout
  10. Moved LED towards corner and added resistor to LED circuit
  11. No longer optimised for home etching 🙁
  12. License changed to GPL v3 or newer
  • v1.2 January 04, 2011
  1. Added 0.1″ motor connector to RAMPS for each driver (motors no longer have to be connected on top of stepper drivers)
  2. Added breakouts for serial and I2C
  3. Changed extra power and pin headers around for easier connection to extra boards.
  4. Lost most extra analog breakouts
  5. More silk screen and bottom layer fixing
  • v1.1 September 30, 2010
  1. Replaced power barrel jack with plug-able screw terminal
  2. Added jumpers to select micro-stepping on stepper driver boards
  3. Added debug LED
  4. Changed mosfet pins to be compatible with FiveD firmware
  5. Reduced number of 100uF capacitors to 1
  6. Added 100nF capacitor to 12V input
  7. Put auxiliary 12VIN and GNDIN pads in a straight line
  8. Silk screen and bottom layer cleaned up
  • v1.0 Original RAMPS PCB design
  • v0.1? Point to point wired Arduino MEGA Prototype shield

    Troubleshooting

    • Check List
    1. RAMPS shield firmly seated on Arduino MEGA
    2. No stray wires/metal to cause short
    3. All connections firmly seated, screws tight
    4. Power connection oriented correctly, connected to RAMPS shield (only USB is connected to MEGA)
    5. Thermistor connected to T0
    6. Firmware uploaded
    7. Stepper driver potentiometers to a sane setting (maybe 25% from CCW to start, adjust to enough power to drive axis + not overheat)
    8. Heater wires properly connected
    • Cannot connect?
      • Verify firmware and host software baud rate matches
      • Disconnect USB, reconnect, and retry
      • It may be a problem with the software you’re using (repsnapper). Try using pronterface.
    • Stepper motor getting too hot?
      • Adjust the potentiometer (small screw) on the stepper driver in question by rotating the screw counterclockwise to decrease the current going to the stepper motor.
    • My fan is not working.
      • If you have RAMPs 1.3+ and sprinter firmware (set with the default pins for RAMPs 1.3), try attaching the fan to D9 output.
      • In pronterface, the fan can be turned on by using the M106 command and turned off with M107.

    Stepper Driver Testing

    If you are not sure whether you have a problem with your RAMPS or the stepper drivers you can test that the driver is getting the power and signals it needs to work.

    • Stepper motors getting too hot?
      • Adjust the potentiometer (small screw) on the stepper driver by rotating the screw counterclockwise to decrease the current going to the stepper motor.

    Use a meter of some sort to test the signals at one of the motor drivers. Be careful not to short anything out. You can use a (-) pad in AUX-1 for ground and test the voltage on VMOT, VDD, EN, STEP, and DIR. If all of these are working correctly then the stepper driver is likely bad.

                        High(5V) when disabled, Low when enabled  EN-|     |-VMOT  12V (or voltage at 5A side of input power connector
                                                  Set by Jumper  MS1-|     |-GND 0V                 
                                                  Set by Jumper  MS2-|     |-1A     ---------------| <Motor Coil A   
                                                  Set by Jumper  MS3-|     |-2A     ---------------|____
                                         Not used (tied to SLP)  RST-|     |-1B      -----------------/  |  <Motor Coil B
                                         Not used (tied to RST)  SLP-|     |-2B      -------------------/
                                      Pulse High for each step  STEP-|     |-VDD  5V
    Switches between High and Low when driven direction changes  DIR-|     |-GND 0V

     

    Q&A

    • What power supply you recommend for your ramps board. I have just finished assembly and looking at the diagrams for a pc power supply and wondering about the separate amperages for the extruder and heated bed. Can they be higher amps without damage?

    Yes, the power supply being capable of more amps than required is the desired configuration. The current shown are the max supported by RAMPS and is the minimum the power supply should be capable of. It is also OK to have both of the inputs on RAMPS connected to one PSU with enough capacity. If you are not using a heated bed the entire thing can run off the 5A side (D8 will just not work).

    • I got a RAMPS V1.3 as part of a kit, but it doesn’t have any installation instructions – just a schematic. Can you point us to a good tutorial for connecting everything? (i.e. stepper motors, opto flag pcb’s, power, data, etc) Some of it (like the single USB port) is obvious, but some of it isn’t.

    See RAMPS1.3 for instructions for version 1.3. There is a version navigation bar at the top of the RAMPS pages that allow you to jump to a specific versions instructions. There is a very helpful graphic under Final Check section.

    • For RAMPS V1.3 the power section of the schematic shows several places with GND/12V (C4/C6, X4-2/1, X4-4/3, VCC/D12). Which one is the GND/12V from the power supply? Is it the round power plug like a laptop power plug? Also, is the outside of that plug GND while the inside is +12V? My kit came with a note warning not to reverse the input power or it would cook the board . . . and a plug adapter with no labels that can be installed either way.

    See the connecting power section of your version’s page. The round plug is on the Arduino MEGA and will only power the MEGA. You need to power the green pluggable connector, it should not be reversible and the board should be marked (+) and (-).