Michael- Glad things are working out. I have been playing with floppy steppers, and they are probably ok for my application, but where did you get the 'real stump pullers' - I think I could afford $7 each ;-) David michael brown wrote: > 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. -- http://www.piclist.com hint: The PICList is archived three different ways. See http://www.piclist.com/#archives for details.