RepRap + SPaRC

RepRap Prusa Mendel Project (RAMPS 1.4 Board)

The electronics setup that I decided to go with for this RepRap build was the RAMPS 1.4 platform. I ordered the RAMPS 1.4 DIY Kit Complete from Ultimachine with optical endstops and the pre-soldered SMT components. I did feel that it was worth $15 of my time and frustration trying to figure out how to solder all of those tiny parts, and I think it was a good choice. Perhaps the next build will involve using the re-flow oven, but that’s another story.

I am not an amazing solderer by any means, but I do admit that the RAMPS shield (that plugs into the Arduino MEGA board) was relatively painless. I just followed the instructions on the RepRap Wiki RAMPS 1.4 page, and it was put together in about an hour. The wiki mentions a couple of priceless tips on soldering the female headers and the male pin headers that go into the Arduino board. That advice was extremely useful for keeping all the headers lined up and fitting together well.

Below is a photo of the RAMPS board after everything was soldered on:

RAMPS (top)

Top view of the RAMPS 1.4 board after soldering.

The board did not sit flush on top of the Arduino MEGA because the Arduino’s power barrel connector pushed on the power supply input of the RAMPS board. It is not a terribly pressing matter, but it could be solved by desoldering the unneeded barrel connector. I also added the included MOSFET heatsink to Q3 (not included in the picture above), but it was not described in the wiki’s instructions.

The kit also came with four Pololu stepper drivers, so I soldered up the headers to those as per the instructions on the wiki. An issue I came across, however, involved the optical endstop headers. Each of the wires coming from the endstops had a three-pin connector on it, but the RAMPS board only had two male headers for each endstop. I found out that I needed to use some of the spare male headers in the kit and add them to the ‘+’ row under the ‘-’ row for the endstops. I broke off a six-pin segment of header and soldered it to the holes shown in blue below:

RAMPS (optical headers)

Extra header pins required for RAMPS optical endstops.

It was time to add one of the stepper motors and drivers (in case something bad happened, I didn’t want to fry all four drivers), connect it to the computer and test it out! To supply the 12V, 5A required to drive the steppers, I connected the RAMPS board to an old computer desktop power supply unit (PSU). The particular PSU I used could push about 20A of current at 12V, using the yellow (+) and black (-) wires. In order to get the PSU to actually start up with connecting it to a computer’s motherboard, I had to short the green wire to ground (black wire) using an extra bit of wire. I might eventually change this wire to a switch, as the PSU does not have an on/off switch of its own.

I downloaded the most recent Arduino IDE (0022) as well as the Sprinter firmware for use with the RAMPS board. ‘Configuration.h’ has some options that allow you to choose which board you are using, and with some help from DavideV on the RepRap IRC Channel, I was able to determine that the RAMPS 1.4 is compatible with RAMPS 1.3 software. Therefore ‘#define MOTHERBOARD’ was set to ’33′ (for RAMPS 1.3).

After connecting the board to the computer (running Ubuntu 10.04 Lucid Lynx) with the USB cable, I selected the correct serial port in the Arduino IDE, selected the Arduino MEGA 2560 platform, and clicked upload. It uploaded successfully, so I downloaded RepSnapper (the software that is used to send commands to the RAMPS board) and fired it up. Unfortunately, the stepper motor would not move when I tried to send it manual move commands. Going back to the IRC channel (which is probably one of the best help sources for RepRap, ever), johnnyr helped me discover that the baud rate in RepSnapper was not set to the correct rate for the RAMPS Arduino MEGA, ’115200′. After changing that, I was able to move the stepper motor with move commands in one direction but not the other. johnnyr said that it was because I had not connected the endstops yet, which would let the motor move in the negative direction.

I still need to wire up the optical endstops, but other than that, the electronics are fully operational! I still need to build the chassis/frame, hotend, and extruder, and I will probably assemble the chassis next. If you have any questions about my electronics setup are need any help on your own, leave a comment below, and I’ll do what I can to help!

RAMPS with stepper controllers

Final RAMPS assembly with stepper controllers mounted. (disregard that backwards stepper motor driver. It was never powered on like that, I promise.)

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