gshapiro@wpi.wpi.edu (Gregory N. Shapiro) (06/10/89)
Does anyone have any information on how to get a computer to control the running of a stepper motor through it's serial port. The computer I would like to use is a Macintosh. If anyone has any information regarding this topic, please mail it to me. Thank you. Greg ____________________________________________________________________________ Gregory Shapiro Gregory Shapiro Worcester Polytechnic Institute Worcester Polytechnic Institute GSHAPIRO@WPI.BITNET Box 1397 GSHAPIRO@WPI.WPI.EDU (130.215.24.1) 100 Institute Road GEnie: THE.CYCLOPS Worcester, Massachusetts 01609 MacNet: GShapiro United States ____________________________________________________________________________
jack@csccat.UUCP (Jack Hudler) (06/11/89)
In article <2668@wpi.wpi.edu> gshapiro@wpi.wpi.edu (Gregory N. Shapiro) writes: >Does anyone have any information on how to get a computer to control >the running of a stepper motor through it's serial port. The computer >I would like to use is a Macintosh. If anyone has any information >regarding this topic, please mail it to me. Thank you. > Greg You might try Alpha Products, they have primitive stepper controller, (sorry it might not be primitive to you but they are to me) and for the money it does quite a bit. I have use them on several projects and have had no problems. As for the serial, I have never use that method to interface to the controller but they do have it. You will find ad's for them in Byte magazine. Alpha Products 242-B West Avenue Darien, CT 06820 +1 203 656-1806 -- Classic Quotes from STNG: "Pen Pals" Picard: Her society is aware .. that there is intersteller life? Data: No Sir. Picard: Oooops..
ehm@raider.MFEE.TN.US (Erik H. Moe) (02/03/90)
I'm working on a project involving the use of a stepper motor. Not being really familar with these devices, I was hopeing to solicit a little information. The motor has three phases. I have been able to step the motor using as little as 1.5V, however to get the torque and the speed needed, it will take a lot more voltage to make it go. According to the specs on the back of the motor, the nominal input voltage is 28V. My question is whether this is continous? In a short duration pulse, the current would be limited by the inductance of the windings, however, I interested in how much continous dc the motor could take. I'm afraid of buring it up. Help ehm@raider.mfee.tn.us
jhuang@sci.ccny.cuny.edu (Jian Huang) (02/04/90)
In article <169@raider.MFEE.TN.US> ehm@raider.MFEE.TN.US (Erik H. Moe) writes: > >I'm working on a project involving the use of a stepper motor. >Not being really familar with these devices, I was hopeing to >solicit a little information. The motor has three phases. I have >been able to step the motor using as little as 1.5V, however to >get the torque and the speed needed, it will take a lot more voltage >to make it go. According to the specs on the back of the motor, >the nominal input voltage is 28V. My question is whether this >is continous? In a short duration pulse, the current would be >limited by the inductance of the windings, however, I interested >in how much continous dc the motor could take. I'm afraid of >buring it up. > > > Help > ehm@raider.mfee.tn.us Yes, it should be continous. That is why the stepper has static torque. As you guessed, it will get less current when it spin faster. So the smaller torque at higher speed is a disadvantage of stepping motor. In order to overcome this, some complex drivers use dual voltage circuitry in which the higher one apply to motor when it is runing and the lower one when resting. -- JIAN HUANG System Software Engineer jhuang@sci.ccny.cuny.edu Klinger Scientific jhuang@ccnysci.uucp Garden City, NY 11530 jhuang@ccnysci.bitnet (516)745-6800
shawnd@coho.ee.ubc.ca (Shawn Day) (11/07/90)
Hello. I tried posting this message last week but it doesn't seem to have worked. I'm sorry if this is a repost. We are planning on building a stepper motor drive system for tracking & slewing a 12 1/2" telescope. If anyone has any experience in this type of thing, we would appreciate hearing your comments. Specifically, we need to find a source for inexpensive stepper motors. Our current calculations indicate that we need motors with about 260 oz-in torque and a speed of at least 40 RPM. Also, we would be interested in any stepper motor controller circuits which may help us with our project. Shawn & Dave. Shawn Day (604) 264-0024 #104-8777 Hudson Street shawnd@fs1.ee.ubc.ca Vancouver, British Columbia ...!ubc-cs!fs1.ee.ubc.ca!shawnd Canada V6P 6H2
whit@milton.u.washington.edu (John Whitmore) (11/07/90)
In article <1436@fs1.ee.ubc.ca> shawnd@coho.ee.ubc.ca (Shawn Day) writes: > >We are planning on building a stepper motor drive system for tracking >& slewing a 12 1/2" telescope. > > ... we need to find a source for >inexpensive stepper motors. Our current calculations indicate that >we need motors with about 260 oz-in torque and a speed of at least 40 RPM. > 260 oz-in of torque is a LOT of torque for most small (cheap) stepper motors; for that much torque, the shaft diameter is 3/8" and used ones go for about $70. Also, 40 RPM is very slow for a stepping motor; typical speeds are 300 RPM and up. So, it looks like you should consider different gearing (finer screw on your worm drive?). At 400 RPM/26 oz-in, there's a LOT of standard size 23 stepper motors that will do your job. Size 23 is 2.3" diameter (or 2 7/32" if you insist) and mounts with four screws at the corners of a 1 7/8" square (with the shaft in the center of the square. Now begins the fun. Old disk drives (those 8" jobbies no one wants) used nice big stepper motors for the head positioning; 5 1/4" floppies might have used one for the spindle motor; lots of machines have a few steppers inside. Go junkyard-prospecting! Any stepper big enough will likely be usable (the things are hard to destroy). If you don't want to do the search yourself, get in touch with C and H Sales Co. 2176 E. Colorado Blvd. Pasadena, CA 91107 (800) 325-9465 and ask 'em. My catalog (a year or so out of date now) lists SSM8550 as a used 35 oz-in/ 5V/ 1A stepper for $19.95. Torque achieved at any given rate will depend on your drive circuitry (current source with high compliance, i.e. high voltage and a big resistor, is best). Integrated circuit drivers are available (but probably hard to find in small quantities); check Sprague databooks. It's easy to build controllers with transistors and logic circuits, though it can be challenging to arrange controls (one knob for speed, and a switch for direction? Knob with forward/backward speed control? Old Macintosh mouse with amplifiers on the four output wires? Preset thumbwheels and push 'go' button? Constant speed set by crystal clock? ... ) The possibilities are endless. The basic principle is to generate square-wave current drive for the two windings which are out of phase (90 degrees out of phase gives the most even torque). Stop the square waves (i.e. set the frequency to zero) to stop the motor. If the motor has center-tapped windings, there will be six wires; connect the center tap through resistor to +V and ground the other two through switching transistors (takes four transistors). If the motor has split windings (eight wires) you can just connect 'em together and use like a six-wire type. If the motor has simple windings (four wires) you have to have twice as many transistors (H configuration); you won't find this in any but the tiniest of steppers. Alas, I can't recommend any books on the subject. I just sort of picked up things from manufacturers (Airpax, Superior Electric Co.) and eventually didn't need any more information. John Whitmore
gbt@sequoia.cray.com (Greg Titus) (11/07/90)
In article <10700@milton.u.washington.edu> whit@milton.u.washington.edu (John Whitmore) writes: >In article <1436@fs1.ee.ubc.ca> shawnd@coho.ee.ubc.ca (Shawn Day) writes: >> >>We are planning on building a stepper motor drive system for tracking >>& slewing a 12 1/2" telescope. >> >> ... we need to find a source for >>inexpensive stepper motors. Our current calculations indicate that >>we need motors with about 260 oz-in torque and a speed of at least 40 RPM. >> > 260 oz-in of torque is a LOT of torque for most small (cheap) >stepper motors; for that much torque, the shaft diameter is 3/8" >and used ones go for about $70. Also, 40 RPM is very slow for a >stepping motor; typical speeds are 300 RPM and up. So, it looks like >you should consider different gearing (finer screw on your worm drive?). John's right. Shawn, a smallish but useful article on stepper motor driver circuit design and associated topics appeared in Sky & Telescope I believe last year. Check the Reader's Guide To Periodic Literature. greg -- -------------------------------------------------------------- Greg Titus (gbt@zia.cray.com) Compiler Group (Ada) Cray Research, Inc. Santa Fe, NM Opinions expressed herein (such as they are) are purely my own.
steve@monu6.cc.monash.edu.au (Steve Balogh) (11/07/90)
In article <10700@milton.u.washington.edu> whit@milton.u.washington.edu (John Whitmore) writes: > Now begins the fun. Old disk drives (those 8" jobbies no one >wants) used nice big stepper motors for the head positioning; 5 1/4" >floppies might have used one for the spindle motor; lots of machines >have a few steppers inside. Go junkyard-prospecting! Any stepper big >enough will likely be usable (the things are hard to destroy). A great source for stepper motors are old computer printers. The old QUME and DIABLO daisywheel printers had excellent steppers in them. Some of the big "line" printers used with minicomputers are a good source for LARGE steppers. Also check old tape drives, card-readers/punches, etc. Check out your local Computer Centre for any junked or unused printers! :-) Steve ----_--_-_-_--_-__-_------_-__---_-___-_----_-____-_-_--__-_--_--___-_-_-_--__-_ Steve Balogh VK3YMY | steve@monu6.cc.monash.edu.au Monash University (Caulfield Campus) | 37 52'38.8"S 145 02'42.0"E ...ICBM PO Box 197, Caulfield East | +61 3 573 2266 Voice (Office) Melbourne, AUSTRALIA. 3145 | +61 3 571 3646 Fax