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Our project is to build a set of CNC components that can easily be assembled in many different ways to create one incredible machine. Read more

Minneapolis, MN Hardware
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This project was successfully funded on March 31, 2012.

Our project is to build a set of CNC components that can easily be assembled in many different ways to create one incredible machine.

Minneapolis, MN Hardware
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CNC Electronics, Features and Datasheet

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We've been getting many questions in regard to the CNC Electronics kit we are offering in the $50, $100 and $200+ rewards. Hopefully this will answer all the questions that are floating around out there. (We'll also be updating our FAQ section).

Our CNC Electronics are a 3 Axis Unipolar CNC Controller. Signals come in from the computer via a parallel port (or printer port). Software will be required to interface with the board. Mach3 is available for Windows & EMC is available for Linux.

The onboard motor control chips are the SLA7078MPR from Allegro Microsystems. Some features of our CNC Control Electronics are:

  • Accepts 5, 6 or 8 wire unipolar stepper motor (4 wire type not compatible)
  • 40 volt DC maximum input voltage, 24 volt DC recommended, 12 volt DC minimum.
  • 3.0 amps maximum current per phase, 0.5 amp minimum. (Fully adjustable)
  • 12 volt DC output for computer style case fan.
  • 1/2, 1/4, 1/8, & 1/16 microstepping.
  • Patent pending circuit protection built in to protect against short circuits.
  • Inputs for limit switches and e-stop.
  • Easy to build and easy to use terminal blocks for connecting wires.

Step / Direction control information:

  • X-Direction: Pin 2
  • X-Step: Pin 3
  • Y-Direction: Pin 4
  • Y-Step: Pin 5
  • Z-Direction: Pin 6
  • Z-Step: Pin 7
  • Limit Inputs: Pins 10 - 13
  • E-Stop Switch: Pin 15

We've attached a photo of the board layout (which is subject to change). The connection on the top are for the 3 individual motor controls. From left to right are the X-axis, Y-axis and Z-axis connections. The blue boxes with the yellow dial are a potentiometer for adjusting the amperage from 0.5 to 3.0 amps. The black box with switches controls the microstepping for each axis. The blue terminal hook up to the left of the parallel connector is for a 12 volt DC case fan (optional), and the terminal hook up to the right is for the limit switches and e-stop button (optional). The power hook up (not shown in photo) is in the center of the board. There are various other resistors, regulators and capacitors on the board, but the part count is very low which makes assembly easy.

Also attached is a copy of the SLA7078MPR circuit for controlling unipolar stepper motors. You can find a copy of this schematic as well as the definitions and configurations in this technical document on the Allegro Microsystem website.

If anyone would like to help improve this circuit by assisting with additional features, we'd love to hear from you!

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Comments

    1. Creator AJ Quick on March 7, 2012

      Also. Heat sinks are not required if you are running low current motors and have the power turned down. If you are planning on running 3A they are necessary to avoid overheating.

    2. Creator AJ Quick on March 7, 2012

      Yes. There is a full 3/8-1/2" between the chip and the capacitor. It is no problem to install a heatsink directly to the motor control chip. It is supported nicely between the 3 chips. You can see a picture of a (non-conventional) heatsink installed on the chips here: http://sphotos.xx.fbcdn.net/hphotos-ash4/419795_362145290484789_176389105727076_1190142_1465370060_n.jpg

    3. Creator David Snell on March 7, 2012

      Looking at the picture, is there any plan for heatsinks to be mounted to the Allegro chips? Looking over their spec it seems like they may be a good idea in certain situations but the picture does not appear to show any board mounting points (since a heatsink should not be physically supported by the chip it is on) and there may be a clearance issue with the capacitor on the left.