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Jeremy, you might be the wrong expert to contact about this but since your an arduino exper and im utilizing an arduino uno in my project i thought i might give it a shot, im trying to build a micro cnc laser engraver, the only problem im expiriencing right now is that the stepper motors i salvaged out of an old dvd drive have no labels on the 4 contacts that come out of them, im not really sure how to connect them or how to test which terminal is which without burning anything. I also looked online trying to find any type of documentation for the motor i got but there is nothing out there, the numbers that are on it are : s42 7917c3a, im not really sure if thats a serial or model number. If you have any idea how i could test it out i would greatly appreciate your help, i will be driving them with an arduino uno and an easy driver i got from spark fun.

thanks

bart

I think you are going to have a lot of fun with this project that you have in mind.

The motors are probably usually driven with 12 volts from the PC, so do not try and use more than that, unless you buy some really good driver chips (either to build your own driver, its not difficult, or you buy PCBs already built and tested....) that handle current adjustment, which will allow higher voltages also to be used. Allegro make some good chips, I can recommend the Allegro family chips, especially the latest ones that do not need external sense resistors......Look at the SLA707X family of chips.

You need to be careful in adjusting just how much current is sent to the motors, may I suggest not more than say 250 ma at first, and if the motors get hot, both cool them and use less current. The current is adjusted by setting up a specific chip voltage using a pot. The chips come in various max currents up to 3 amps per motor, you only need the chip with the lowest current range, 1 amp range.....

Then you will need usually 3 axis for engraving, so that means 3 motors and 3 driver PCBs. (Change to 4 if needed!)

Then, assuming you want to get going fairly quickly and have an easy interface to faultfind, go for a Parallel Printer Breakout Board (often just called a PPP) and an older (cheaper) PC with a PPP, or one where you can by a plugin card with a port on it.

DON'T GO FOR USB, learn to walk before you run. Also USB costs far more in both $$$ and nerves!

Then find and download an Ubuntu Unix install with EMC2 (all free from Sourceforge). Read here first:-

http://en.wikipedia.org/wiki/SourceForge

Join the EMC forums and get yourself up to speed.

Look for other forums CNCZONE and the like, read all you can.

If you buy or make a breakout PCB, make sure it has opto isolation. To read more on this, join the yahoo group:-

http://groups.yahoo.com/group/DIY_CNC_Interfacing/

You will eventually need to get a good CAD program, there are some free ones around. Then the drawing needs to be converted to GCode for your CNC machine. You can read more about GCode here:-

http://en.wikipedia.org/wiki/Gcode

If you have any further questions I and others here can help, just ask.

regards

Andy

I forgot to mention that with an Arduino, you can contrly MOSFETs to drive the stepper motor directly, sorry!!

Maybe someone has already developed code that you can use or adapt.

As your motor has 4 connections, that is a BIPOLAR Stepper Motor. Not a Unipolar!!! Never forget that!!

Its easy to identify both coils simply by using an Ohmeter on Ohms. Each coil will have two connections, label them coil A and coil B. If the motor ever drives the "wrong" direction, you only need to reverse the connections to ONE COIL ONLY!

Sorry that I forgot so much.....

regards

Andy

Yes, Andrew is correct.  Referring to this diagram might help you understand better: http://www.robotgear.com.au/Cache/Files/ProductImageOriginals/679_Bipolar%20stepper%20motor%20wiring%20diagram.jpg  You can use the continuity function of a multimeter to identify the wires.

Yes, Andrew is correct.  Referring to this diagram might help you understand better: http://www.robotgear.com.au/Cache/Files/ProductImageOriginals/679_Bipolar%20stepper%20motor%20wiring%20diagram.jpg  You can use the continuity function of a multimeter to identify the wires.

Im actually trying to follow this instructible: http://www.instructables.com/id/Pocket-laser-engraver/ this is my first project with an Arduino or any type of a micro controller but i thought it would be a good prelude to building a full size cnc router, anyways i can identify the two seperate coils on the motor but how do i know which is contact is a, c, d, b? i tried applying voltage (first 3.5 V then 5V) to each one of the coils but i got no movement out of them, also i thought that dvd drives run or 5v instead of 12v so i will try applying 12v tomorrow, if it burns out then too bad i can always salvage another motor out of a different drive. I was also think about just running some g code to the controllers so it would be constantly putting out a signal to the motor and breadboarding my easy driver so i could easly plug in the wires from the motor and just try different combinations im just afraid of damaging the driver board so please let me know if thats a bad idea. i will try to get  apicture of my motor as soon as my camera charger comes in as i lost it on vacations and my battery died compleatly, once again thanks for all the great help!

Stepper motors ONLY understand a complex sequence of pulses, on one or the other coils in either of two directions, you cannot drive them with DC power!! You may just burn out a coil and destroy the motor completely.....

TIP. Never apply power to something you don't understand.......it can even be dangerous to you personally, but not in this case, it was only dangerous to the motors......

There are no contacts in a stepper motor.

A picture is unlikely to help further.

Look for tutorials and the like on the web, read before proceeding further.....

Best wishes.

Andy

Hi, what is the   pin number ATMEGA328P-PUATMEGA328P-PU  input power, and ground, I have connect output 0 led positive, and ground negative, how connect correct wire to atmega's pins?, final led blinked.

Thanks for answer

Bye

You should download yourself an Arduino board schematic so you can see what goes where.The design files (.pdf and Eagle) can be downloaded from here:

http://arduino.cc/en/Main/ArduinoBoardUno