Author Topic: Manual operation of a stepper motor....without electronics.  (Read 10283 times)

Offline John Hill

  • The Artful Bodger
  • Madmodder Committee
  • Hero Member
  • *****
  • Posts: 1978
  • Country: nz
Sometimes a project calls for the manual turning of a shaft by some means other than simply attaching a handle or a knob.  For example, you have some shaft geared down that you want to rotate by known discrete amount or steps,  maybe this device is out of convenient reach.

You could fit a stepper motor and some electronics to send a known number of step to the motor or perhaps such electronics is not your forte or the environment is not conducive to reliable electronics.

I had a requirement some time ago to adjust the components of an aerial tuning unit for a HF transmitter that was mounted at the aerial mast some distance from the operating position.  Stepper motors were obvious candidates but the high intensity RF fields would play havoc with electronic circuits, so I made a manual stepper control.

Here is the mockup I used to test the concept (sorry about the dust)! 


The manual control is a multi position switch which is wired to energise the coils of the stepper motor in sequence,  the stepper motor is from an 8" floppy drive but one from a printer would be just as suitable.  The terminal strip has nothing on it except diodes to protect the switch contacts and a couple of sockets for plugging in the 12V supply.

Connect the power to this board and turn the knob the motor turns too in the direction and at a ratio according to the design.

Supposing you had a 12 position switch (not hard to find at the usual electrical and radio suppliers) and you had a 7.5 degree stepper motor you would be able to configure these so that one turn of the switch makes 12 steps of the motor, or 90 degrees.  So you have a nice 4:1 reduction, with the same type of switch and using half stepping you would have an 8:1 reduction and so on according to your choice of motor and switch.

Of course the switch does not have to be turned manually,  consider for example that you mounted a switch on your mill spindle and the stepper on a feed screw you would then have power feed in a set ratio to spindle speed and you could change the ratio by switching out some of the switch contacts.  Staying with your 12 position switch and the 7.5 degree motor you could reduce the feed ratio down to 48:1 or even 96:1. Of course the feed would stop or start with the spindle.

Almost all multi position switches have a stopper to prevent 360 degree rotation but except for the modern all sealed plastic ones you can usually easily remove the stopper, check before buying.
From the den of The Artful Bodger

Offline Weston Bye

  • Jr. Member
  • **
  • Posts: 90
  • Country: 00
  • Grand Blanc, Michigan
Re: Manual operation of a stepper motor....without electronics.
« Reply #1 on: July 12, 2009, 08:52:31 AM »
John,
An excellent and inexpensive solution for a little used stepper motor.  Not to steal your thunder, here is how I approached the subject in an article in Digital Machinist:





I used a cam to trip a couple of roller-lever microswitches.  The arrangement generated 4 steps of the motor for each revolution of the cam.  I used a couple of flanged ball bearings (overkill) from an old floppy drive.

Weston Bye
Practitioner of the Electromechanical Arts.
author of The Mechatronist column
Digital Machinist magazine

Offline John Hill

  • The Artful Bodger
  • Madmodder Committee
  • Hero Member
  • *****
  • Posts: 1978
  • Country: nz
Re: Manual operation of a stepper motor....without electronics.
« Reply #2 on: July 12, 2009, 02:36:34 PM »
Excellent diagrams Weston! :thumbup:  Saves me having to draw them.

Did you find a speed limit with the micro switches?

In my application what I really needed at the time was a "remote knob"  that would not get upset by the high power standing waves in the cable way but in the future I intend to make a power feed for the vertical on my little shaper and I am undecided between a stepper and a bicycle brake cable!
From the den of The Artful Bodger

Offline dsquire

  • In Memoriam
  • Hero Member
  • *****
  • Posts: 2275
  • Country: ca
  • Kitchener, Ontario, Canada
Re: Manual operation of a stepper motor....without electronics.
« Reply #3 on: September 24, 2009, 04:04:20 AM »
John

Somehow I managed to miss this one but now that I have found it I am marking it and going to play around with it. I have been looking for something like this for a long time and could never find anything for simple manual control. Thanks :ddb: :ddb:

Cheers  :beer:

Don

Good, better, best.
Never let it rest,
'til your good is better,
and your better best

Offline Gerhard Olivier

  • Sr. Member
  • ****
  • Posts: 314
Re: Manual operation of a stepper motor....without electronics.
« Reply #4 on: September 24, 2009, 04:55:09 AM »
Don Look at this one


I dont undertand any electronics but this looks Promising????  It's not completely manual but could be used that way??????

Gerhard
Guernsey
Channel Islands

Offline John Hill

  • The Artful Bodger
  • Madmodder Committee
  • Hero Member
  • *****
  • Posts: 1978
  • Country: nz
Re: Manual operation of a stepper motor....without electronics.
« Reply #5 on: September 24, 2009, 05:06:40 AM »
Don, the diagrams by Weston Bye are excellent and I recommend anyone considering a manual control of a stepper motor to take a lead from them.  His technique is much better than mine as it makes full use of the stepper motor whereas mine is a lot simpler and only a fraction of the power for the same size motor.
From the den of The Artful Bodger

Offline dsquire

  • In Memoriam
  • Hero Member
  • *****
  • Posts: 2275
  • Country: ca
  • Kitchener, Ontario, Canada
Re: Manual operation of a stepper motor....without electronics.
« Reply #6 on: September 24, 2009, 12:45:27 PM »
John

Thanks again. What you have shown in its simplest forum is what I am looking for. :coffee:

Weston Bye

Thanks for your post. This info will certainly be looked at and played with.  :coffee:

Gerhard

Thanks for the link. I watched the video and very interesting. It is a bit more than I want right now but will keep it for future reference. :coffee:

Cheers  :beer:

Don

Good, better, best.
Never let it rest,
'til your good is better,
and your better best