ypham@jarthur.claremont.edu (Yen) (05/09/91)
Hello netters, I am doing a project that need a stepper motor. I was able to found some from a junk box. Now, are there any standard to the wiring to these motors? What is the drive circuit needed to drive one of these motor looks like? I would appreciate some pointers, or the sources I should seek for helps. I remember that somebody posted a note about this last year on this news group. How can I find this article again? THANKS IN ADVANCE, YEN
grege@gold.gvg.tek.com (Greg Ebert) (05/11/91)
In article <12076@jarthur.Claremont.EDU> ypham@jarthur.claremont.edu (Yen) writes: >Hello netters, > >I am doing a project that need a stepper motor. I was able to found > > [...] There are 2 types of steppers I know of: 4-wire and 6-wire. In the following discussion, the word 'high' means a DC source. It can be positive or negative. About 12-15 volts usually works. Each state is about 3-10 milliseconds for a "typical" stepper. To be safe, start out with small voltages and time intervals, then work your way up if you need more torque or if it's too fast. *****REMEMBER***** You have inductive loads! Makes sure you provide a return path with a reverse-biased diode. If you aren't nice to inductors, they will get revenge ! 4 wire: There are 2 separate windings. Use an ohmmeter to identify them. Call the wires on the first pair A and B; The second pair C & D To make the motor rotate, do the following sequence: A=high B=gnd C=open D=gnd A=open B=gnd C=high D=gnd A=gnd B=high C=gnd D=open A=gnd B=open C=gnd D=high (repeat) If the motor just vibrates, interchange A & B. To reverse, do the sequence backwards. - - 6 wire: There are 2 separate center-tapped windings. Use an ohmmeter to identify them; the lowest resistance means you found the center tap. Tie both center taps to high. Call the remaining 2 wires on one winding A & B. Call the last 2 C & D. The sequence is: A=gnd B=open C=open D=open A=open B=open C=gnd D=open A=open B=gnd C=open D=open A=open B=open C=open D=gnd (repeat) If the motor just vibrates, interchange A & B. To reverse, do the sequence backwards. - - - You can do half-steps by logically ORing adjacent states.
rzh@phoenix.ocf.llnl.gov (roger h hanscom) (05/14/91)
In article <2309@gold.gvg.tek.com> grege@gold.gvg.tek.com (Greg Ebert) writes: >In article <12076@jarthur.Claremont.EDU> ypham@jarthur.claremont.edu (Yen) writes: >>Hello netters, >> >>I am doing a project that need a stepper motor. I was able to found >> >> [...] > >There are 2 types of steppers I know of: 4-wire and 6-wire. In the ^^^^^^^^^^^^^^^^^^ .....remainder of article deleted for the sake of brevity..... What about 10-wire where each of the 5 pairs seems to be one winding, and there are no cross connections between them (motor is of German origin, I believe)??? roger icf!rzh@lll-winken.llnl.gov rzh@phoenix.ocf.llnl.gov rzh@llnl.gov
mzenier@polari.UUCP (Mark Zenier) (05/16/91)
In article <844@llnl.LLNL.GOV> rzh@phoenix.ocf.llnl.gov (roger h hanscom) writes: >In article <2309@gold.gvg.tek.com> grege@gold.gvg.tek.com (Greg Ebert) writes: >>In article <12076@jarthur.Claremont.EDU> ypham@jarthur.claremont.edu (Yen) writes: >>>I am doing a project that need a stepper motor. I was able to found >> >>There are 2 types of steppers I know of: 4-wire and 6-wire. In the > >What about 10-wire where each of the 5 pairs seems to be one winding, >and there are no cross connections between them (motor is of German >origin, I believe)??? A better stepper motor taxonomy has 3 components. 1. Basic Mechanism. (a) Variable Relectance (b) Permanent Magnet 2. Number of Windings. (2 to 5) 3. Winding wiring. (a) Bipolar Drive (b) Unipolar Drive The basic mechanism that generates the torque comes in two basic flavors, (If you avoid some real oddballs that are only used in clocks and the like). Variable Reluctance steppers work like a solenoid. You energize a winding and the rotor assumes a position that minimizes the magnetic "path". The advantage is lower rotor mass, and higher speed. VR stepper can be identified by having no detenting (cogging) when they are powered off. With no detenting, they won't keep position when powered off, an advantage for Permanent Magnet steppers, depending on the application. VR steppers have at least 3 windings, otherwise they couldn't determine which direction they would move. The polarity of drive (positive/negative current) doesn't matter. Permanent Magnet steppers have magnets built into the rotor. The windings create magnetic fields which cause attraction and repulsion forces with the magnets in the rotor. The polarity of drive matters. A Hybrid stepper is a PM stepper with some Variable Reluctance structures to increase performance, usually a higher top speed. PM steppers usually have 2 windings, although the strange ones mentioned above have up to 5. (Something to do with minimizing the variation in torque, as I remember it.) The winding wiring comes down to 2 wires per winding (Bipolar Drive), where when you to reverse the current through the windings, you have to reverse the applied voltage. You either need two power supplies, or an H drive circuit. Or 3 wires per winding means a Unipolar Drive. The winding is split in half (usually bifilar, two windings wrapped the same). To create a magnetic field of a given polarity, you pass a current through the center tap of a winding and one end. To create the opposite polarity field, you send the same polarity current between the center tap and the other end of the winding. Turning both on at the same time is a waste of power, as the fields should cancel. Usually the center tap is connected to the power, and the driver circuit grounds one end or the other. If you can ignore the center tap, (Hard to do in a 5 wire motor where the center taps of two windings are connected), you can treat a Unipolar winding as a Bipolar one. Some things to remember with stepper motors. Don't expect it to work if you take it apart and put it back together. They are an easily customized product, without much standardization (especially the wiring). You may find the stuff in the surplus market is a one of a kind, or at best a limited run item, and the one next to it in the bin is something very different. They are just wire and magnets, so there is no firm limit to the amount of abuse. They don't have things like breakdown voltages. You ask the manufacturer what it can take, and he says "well, it will melt at such and such temperature". Not only are the windings inductors, combined with the magnets, a stepper motor can be a generator. Drive circuits may have to take this into account. For some neat stuff check out the SGS-Thomson "Industrial and Computer Peripheral ICs" databook. For serious engineering stuff, check for the proceedings of the annual conference on "Incremental Motion". And literature from manufacturers like Hurst and Sigma. Mark Zenier markz@ssc.uucp mzenier@polari.uucp