Step 5: Electronics
In the schematics I have added a relay for use with a fan. This can come in handy as the engraving produces some smoke.
The Easydriver have two pins called MS1 and MS2, these sets the step sequence. Tie them both to the five volt output from the Easydriver. This sets the step sequence to micro stepping . The four pins from the stepper connect to the motor output. All steppers I have found have all had the same pinout on the small connecting PCB. Connect the pins in the same order to the Easydriver as on the connecting PCB. The control pins (step, dir, gnd) goes to the Arduino. Besides this the Easydriver needs motor power connected. I use a twelve volt wall wart that drives the motors, fan and Arduino. There is a potentiometer that controls the power to the motors, I just set this to the lowest setting and turn it up a tad if the steppers don't have enough force. I don't know the rating on the steppers, if they gets to hot you’re driving them to hard.
The fan just needs to be connected to the fan output. A small computer fan works well, just connect the positive and negative leads to the correct output.
The laser driver is an LM317 based circuit with no specials. This will work fine but it is far from optimal. I am driving the laser diode far too hard at about 300mA and if you do that you can’t expect a very long life for the diode. The best solution would be to find a stronger laser and better driver but to keep to the spirit of things I wanted to use the laser from the DVDR itself. Laser on/off is controlled by the same relay as the fan.
If you want to simplify you could skip the whole laser driver and use a readymade driver. Then all you would have to do would be to connect the power to the fan relay. Of course this would probably be a little bit more expensive.
The whole thing evolved into a new Arduino shield, the Laser Shield. I have included the schematic and board layout in Eagle format . Creating a circuit board is a bit out of the scope for this instructable, but there are lots of really good guides here on Instructables.
If you want to make your own layout with Easydrivers I have made a Eagle library with the driver, it can be downloaded here .