I’ve had a few questions about my electronics, so here’s a quick description of my setup.
Currently, the electronics for my RepStrap look like this:
The lower unit consists of a Seeeduino Mega with an expansion board of my own design.
The Seeeduino Mega is an Arduino Mega clone that incorporates a bunch of nice improvements, and is smaller and quite a bit cheaper. Since MakerBot is moving to the Arduino Mega for their next generation motherboard, it seemed like a good time to make the switch.
Here’s a closer shot of the board:
As you can see, I had to fix a couple missed airwires…
The board includes:
- 4 RepRap compatible stepper connectors
- RS485 comms
- E-Stop and buzzer connectors.
The board is powered by the USB connection. The board does not have the “powered” RJ45 connectors for RS485 used on the standard motherboard. Instead, it just has a simple header for the AB connection, which is more in line with the Mendel approach.
I’ve included a fourth stepper connector so that the extruder can be driven directly from this board, rather than the roundabout way that the Mendel uses timing wires between motherboard and extruder. Also, the stepper connections incorporate additional control lines that can be used to select stepping or sleep modes on the stepper drivers.
I’ve tried to keep the board compatible with RepRap/MakerBot. This board currently runs the latest MakerBot Motherboard 2.0 (Mega) firmware with no change.
For the stepper drivers, I wanted to see if an EasyDriver could be used as an alternative to the MakerBot drivers. So I created a breakout board for four of them:
The board incorporates RepRap compatible stepper connectors so it can be used with any current RepRap motherboard. It also has RepRap compatible stepper connectors, and a PC power connector (Molex).
Since the EasyDrivers are microstepping boards, I’ve also included jumpers for the MS1 &MS2 lines which can be used to select the step size (1, 1/2, 1/4, or 1/8). Alternatively, I’ve connected these lines to extra pins on the stepper connectors, so these can be controlled by the Host.
The fourth stepper socket was included for a future stepper driven extruder.
So far, the EasyDrivers seem up to the task. In fact, I’ve been running them with the current set way below max, for smoother running. The Mendel appears to be similar in size and mass to my RepStrap, and uses full ball-bearing axes, so I’d think the EasyDrivers would work well for the Mendel.
If there is any interest in these boards from the RepRap community, I’d be happy to make the designs available, or even get some boards made.
Also, any feedback on the design or overall approach would be greatly welcome!