<x-flowed>Is there a relay (available from Jameco or Mouser) that you recommend I use?
  The motor for this project just says 12V on it.

Some other motors I have just say Vexta DC 1.2Amp, 0.8Amp, and 3.3 ohm, 7.5
ohm respectively.  What voltage and relay should I drive these last type of
motors at?

Greg

> >> All the emitters go to PIC ground, along with the negative of your wall
> >> wart. Positive of the wall wart goes to the common(5 wire) or commons(6
> >> wire) of your stepper. The four collectors each get a stepper lead. Put
> >> resistors between PIC and base! Let's say 220 ohms.
> >
> >Another note here, don't try to run the stepper from the supply that
>feeds
> >the micro.
> >Separate supply (common ground) or batteries is easier to get working.
>
>I can reiterate this advice.  The coils of your motor are giant inductors
>across which you are switching full supply voltage.  When you start running
>the thing quickly it will reset your micro.
>
>When I built a micro-stepper motor driver for an art project I used a
>couple of NPN's to drive the coils of a SPDT relay.  My motor had 4 wires
>and I had to alternate between +/- voltages.  The order of alternations on
>the wires caused to to turn in opposite directions.  The way I figured it
>out is to use a multimeter to figure out which wires went with which coils
>(there will be maybe 100 ohms resistance between pairs of wires).  Then I
>sat there for about 20 minutes with a 5 volt power supply and and touched
>wires here and there until I could get the thing to turn around and learn
>the sequence.
>
>It looked like an encoder :
>00
>10
>11
>01
>00
>
>was CW
>
>and
>
>00
>01
>11
>10
>00
>
>was CCW.
>
>Test out each individual part separately without the micro.... i.e. use
>twisted wires and your relays/transistors to drive the motor by hand then
>hook to your micro.  Make sure you start the pulse counting slow, because
>if you go too fast you will saturate the relays as they have a max switch
>rate.
>
>-Erik Reikes

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