Update It turns out that I *can* tie the center taps together. Once I figured out the sequencing, I was able to get my driver board to make it go. ;-) But I'm still confused as to what is the difference between a 2-phase and a 4-phase vs. uni-polar and bi-polar. I think I understand the difference between uni-polar and bi-polar, but I don't get the 2-phase/4-phase thing. This motor says it is 2-phase, but I am driving it in a uni-polar fashion (no h-bridge) Perhaps any 6 (or 5) wire stepper can be driven in either bi-polar OR uni-polar way??? Perhaps the torque is higher when using it in a bi-polar way (with h-bridge flipping polarity) since you are using the full length of the driven coil (as opposed to half the coil energized at a time) when driving uni-polar)??? The motor did get a little hot, but that's probably due to the fact that I was using 12V to drive a 6V motor (hey they're cheaper than a new 6V gel-cell) With the transistors dissipating twice the power they will have to at 6V, they still didn't get very warm. So, I guess that heat sinks won't be required yet (8 heat sinks cost allot of money) These things are real stump pullers. ;-D I can't believe how much more torque they have vs. the floppy steppers (these are just a tad bit bigger). My little creeper bot will really be able to move now. ;-) Any ideas on some approximately 6" diameter wheels with 3/16 (5mm) shaft size? Sorry so long winded, I'm just trying to provide plenty of information. Michael Brown Instant Net Solutions www.KillerPCs.net "In the land of the blind, he who has one eye is king" ----- Original Message ----- From: "michael brown" To: Sent: Saturday, February 23, 2002 10:58 AM Subject: [EE]: Some stepper motor advice, please > I am working on a robot when I have a little spare time (who isn't ;-D) My > first attempt involved using motors from old 5.25" floppy drives. They are > cheap and easy to work with, but have virtually no power. They are 4-phase > motors, making it easy to drive them. I now need more power, and I found > some cheap(US$7.00) surplus Vexta NMEA-17 2-phase motors. These motors are > rated at 6V .8A. > > My old driver board uses TIP-120's driven thru a buffer IC with extra bypass > diodes added. These had no trouble with the floppy motors even without heat > sinks. > > Now for the questions: > > 1 Since these are 2-phase, do I absolutely have to flip polarity's on the > winding coils to get the motors to run? These motors have 6 wires, so it > seems that they are center tapped. Maybe I can just tie the center taps > together, and drive the motors the way I did the 4-phase motors???? > > 2 Am I going to have to build a new driver board to accommodate the 2-phase > motors. If so, should I just find some type of stepper control IC? > > 3 Do you all think that TIP-120's are stout enough to drive these motors? > 5 watts doesn't seem like too much of a load on a tip-120, is that correct? > I guess I would need to add some heat sinks, though. > > Michael Brown > Instant Net Solutions > www.KillerPCs.net > > "In the land of the blind, he who has one eye is king" > > -- > http://www.piclist.com hint: The PICList is archived three different > ways. See http://www.piclist.com/#archives for details. > > -- http://www.piclist.com hint: The PICList is archived three different ways. See http://www.piclist.com/#archives for details.