ECN Forum Forums General Topics of the Trade General Discussion Area Stepper motors - how to make them operate

I took some of my old printers and a scanner apart to expand my hardware inventory. I found several stepper motors.

There are things I want to rotate, and even partially rotate. If I hook up one of these stepper motors to power, will it just spin? Do these stepper motors require a computer to tell them to work? If they turn a partial rotation and stop, how is that accomplished?

Roger

Links for those interested in running a salvaged stepper motor:


[*]Drivers

Dual Full Bridge Driver L298: http://www.alltronics.com/download/1773.pdf
Push-Pull Four Channel Driver With Diodes L293D http://www.alltronics.com/download/1330.pdf
Push-Pull Four Channel Drivers L293B, L293E http://www.st.com/stonline/books/pdf/docs/1328.pdf
Push-Pull Four Channel/Dual H-Bridge Driver L293C: http://www.st.com/stonline/books/pdf/docs/1329.pdf
Push-Pull Four Channel Driver With Diodes L293 L293DD: http://www.st.com/stonline/books/pdf/docs/1330.pdf
Dual Full Bridge Driver L298: http://www.st.com/stonline/books/pdf/docs/1329.pdf
Stepper Motor Driver Considerations Common Problems and Solutions: http://www.st.com/stonline/books/pdf/docs/1675.pdf
Stepper Motor Driving: http://www.st.com/stonline/books/pdf/docs/1679.pdf
Stepper Motor Driving: http://www.st.com/stonline/books/pdf/docs/1679.pdf
Applications of monolithic bridge drivers: http://www.st.com/stonline/books/pdf/docs/1681.pdf



[*]Controllers

Bipolar Stepper Motor Control: http://www.st.com/stonline/books/pdf/docs/1700.pdf
L297 stepper motor controller: http://www.st.com/stonline/books/pdf/docs/1734.pdf
Stepper Motor Controllers L297/D: http://www.alltronics.com/download/1334.pdf

A stepper motor is a device whose input is an electrical pulse and whose output is the rotation of its shaft. For each pulse the motor recceives, its shaft rotates through a fixed precise angle. Depending on the pattern of pulses applied, the stepper can be used to control the position and/or velocity of a load accurately.
Some advantages are the error is the single step error(usually less than 5% of one step and therefore noncumulative, as opposed to a DC controller which has armature feedback sent to a summing network to help compensate for load changes)
The motor is controlled by drive circuitry and a dc power supply, the circuitry dictates the motors response.
Radio Shack has 555 timers and playing around with the outputs can be set up to control these motors nicely. Also J-K flip-flops work quite nice too.

So am I able to hook the motor up to DC power and a switch, turn it on an run it? Does such a motor require the circuitry you describe in order to run at all?

Thanks for your help!!!

Roger

On a stepper motor, they frequently come with 8 poles whose polarities are changed by switching. the rotor magnetism can be generated by external excitation or a permanent magnet.
A 4 stator winding motor has 8 poles possibly 5 leads coming out of the motor. In order to hook this up properly you will need a wiring diagram because the stator fields are paired these have to recieve a pulse train from the timers. a small dc supply will also be needed.
As stated in a 4 winding stator there are paired fields call them A and A', the second pair B and B'.
A and A' are internally tied together as are B and B'. The center point of each pair of coils is tappen and center point ofBB' is tied to center point AA' a common lead is brought out to make a total of 5 you will need some type of continuity tester to locate the winding leads. the common lead, the center tap receives the pure DC for Excitation, and a series dropping resistor must be used to limit the current to the fields a small pot say 0-5k would work fine.
the other two field leads, once isolated need to recieve the pulse train, the reference for all this can be an output from a 555 timer set up as a one-shot to feed a pair of J-k flip-flops, J-K because you get two outputs from them that is output Q and Not-Q in other words what it is actually a 1 and a 0 when Q goes high Not-Q goes low, all these parts can be obtained from Radio Shack. The inputs J and K must be held high to a 5 volt source and the clocks on the JK receices the input from the 555 timer. Also RS has some literature on Digital circuits and different flip-flops and how they work.
Also the outputs from the flip-flops must be sinked so as not to swamp out the output, this is accomplished with a transistor at each output of the FF ie,Q and Not-Q will recieve a xtr the collectors of the transistors will be tied to the input of the stepper fields.
Give it a try , be creative.

Hell, if I'd known it was that simple, I'd have had one of my kids wire it up!

Just kidding! Seriously, electrical is like heiroglyphics to me, I'm a woodworking and welding type guy, but I wonder if I could just re-use the circuitry and resistor(s) from the printer/scanners I took the stepper motors from. I guess it should be there, right? If not, Radio Shack?

Thanks again for the help!

Roger

Roger,

Just wanted to say, Welcome to the Forum. I was looking at your profile and noticed that the website link doesn't work. You have to put http:// in front of the www or it doesn't work from within this forum. I think that others may find it very interesting.

http://www.johnnyairtime.com/


You've got a pretty intense Job and Hobby there I'd say!

Bill

[This message has been edited by Bill Addiss (edited 09-08-2001).]

Thanks, Bill! I'm glad this forum is here!

I edited my profile, hopefully it will work now!

Roger

Sure you can re-use the circuitry, but you still may have to provide a pulse, most digital circuits are 0-5volts and there is a limit before the electronics will self-dstruct. Cmos are a bit higher, but if it is not cmos it will be about 5 volts.
The driver circuit should still be ok, but you will have to look for the input section, if it came out of a printer the the signal source was probably the pc and the software that provided the info to the driver.
So as I said, good luck.

Thank you VERY MUCH! You've been very helpful. I can see that it's beyond my ability to create a working system with these stepper motors. I've got 5 of them, hopefully I'll be able to use them for something.

Take care!

Roger