Stepper Motor Question

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Bill Gruby

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Not using a stepper motor for CNC, only to move the cross slide in and out for auto-facing, what do I need to drive it and control the speed?

"Billy G" :thinking:
 
Hears some info on steppers

http://homepage.cs.uiowa.edu/~jones/step/types.html

if you dont wish to have positioning a motor may be simpler than a stepper.

Stepper requires the coils to be energised in a sequence that causes reasonably smoth motion, also the pulse rate must be 'ramped' so the stepper has time to accelerate.

You may be able to find a self contained stepper controler that will do that for you or maybe an audrino based driver would be possible.

Stuart
 
Usually a computer to control it and drivers to drive it.

I'm sure someone makes everything in one package but a stupid one that have speed only.

A driver just need something to supply pulses which if you're any good at all with electronics you could build one
using a 555 timer. Use a switch for direction.

Stepper stuff: http://www.kelinginc.net

Good information: https://probotix.com/


Gary
 
GaryK said:
Usually a computer to control it and drivers to drive it.

I'm sure someone makes everything in one package but a stupid one that have speed only.

A driver just need something to supply pulses which if you're any good at all with electronics you could build one
using a 555 timer. Use a switch for direction.

Stepper stuff: http://www.kelinginc.net

Good information: https://probotix.com/


Gary
Click to expand...

yeah thats true you could use an off the shelf psu and step sequencer with a variable frequency pulse input such as a 555 with a way to change frequency to alow for acceleration and de-celeration.

Stuart
 
I only wish to use the stepper motor as if it were a DC motor with variable speed. I want to use it because of its small size. I am thinking Nema 23 w/400+ in oz torque. Can this be done?

"Billy G"
 
Last edited by a moderator:
Bill Gruby said:
Not using a stepper motor for CNC, only to move the cross slide in and out for auto-facing, what do I need to drive it and control the speed?

"Billy G" :thinking:
Click to expand...

I can help you there, but I need a bit of background information:

1) What kind of stepper motor is it? (Bipolar, Unipolar, 3-phase, etc.) Manufacturer and part number would be valuable information.
2) Does the motion need to be dead smooth? (I'm alluding to microstepping)
3) What is your electronics skill level? (Can you build your own circuits from scratch? Or from a kit?)
4) How cost sensitive is your need? (Do you want to buy something ready made?)
5) Do you need position control, or just rate control? (I'm guessing you just want it to feed in or out at a given rate and not precisiely stop anywhere)
6) Presumably simplicity is what you want, right? (No PC, Mach 3, etc.)

There's no question in my mind that a stepper motor is a good choice for your application. While smoothness can be an issue, it can also be largely overcome by either microstepping or voltage control (current control of steppers is fraught with problems - although it appears good on paper if you're just considering I=E/R and ignoring the BEMF).

A brushmotor or a servo motor would not be a good chocie since really all you can do without a closed loop (servo) controller is regulate voltage or current. Voltage regulation which forces the motor to run on it's torque speed curve which means that any changes in required torque will affect the speed. Regulating the current regulates the torque delivered, but speed regulation will still suffer.

Another approach could be a simple brushed DC gearmotor with a large reduction ratio. If the torque capability of the selected motor is selected to be much higher than the required torque, you will get reasonable speed regulation because the reflected load back to the motor shaft will be small in proportion to other losses (friction in the gearbox, viscous losses due to the lubrication, etc).

John
 
Bill Gruby said:
I only wish to use the stepper motor as if it were a DC motor with variable speed. I want to use it because of its small size. I am thinking Nema 23 w? 400+ in ox torque. Can this be done?

"Billy G"
Click to expand...

Wow Bill- that is a project I had on the back burner myself- I even have the 425oz stepper and some hardware. Says "Deepgroove 425oz 2.8A 4V 1.8 Degree"

I was hoping for some sort of "solid state" looking answer to making a dial-speed-operated, reversible drive for the SHerline mill, without getting into software control.

I am meaning to get more into electronics, but I wouldn't mind, for now, a "turnkey" approach depending on the cost.

John, you are blowing me away- but I think I am following you- :)


Bernie
 
Bill Gruby said:
Now we are getting somewhere. Thank you John.

#1 Bipolar

#2 I need auto facing to improve my finish

#3 Average Skill Level. ( Can kit build. never tried scratch building)

#4 What-ever the cost is, it is.

#5 Just need rate control. #6 Big yes on simplicity.

The motor

http://www.ebay.com/itm/1-PCS-NEMA-...398?pt=LH_DefaultDomain_0&hash=item257effb1ee

"Billy G"
Click to expand...

OK. How about this: http://www.piclist.com/techref/io/stepper/linistep/index.htm

The circuit is is only good to 3A, so you'd want to wire your motor with the windings in series... These circuits take three inputs: step, direction and enable. Enable is simply on/off. Direction is obvious. Both direction and enable can come from switches. Step is a bit more complicated. You want to feed this from a circuit to generate pulses that represent your desired feed rate. A frequency generator or a little 555 circuit can take care of this. http://www.ramseyelectronics.com/cgi-bin/commerce.exe?preadd=action&key=UT5

Here's another one from the same distrbutor as your motor: http://www.automationtechnologiesin...rs/kl-4030-24-40vdc-3-0a-microstepping-driver It also requires generation of step, direction and enable.

A thrid option is basically turn key - just build it and go. Again no microstepping, but it gives you a front panel control of speed, on/off etc. http://www.ramseyelectronics.com/cgi-bin/commerce.exe?preadd=action&key=SMD1C

My only concern with not microstepping comes if you drive the motor too hard or rigidity of your cross slide is an issue. I hate to see the motor's vibration ending up on your workpiece. ut at $40 for a non-microstepping controller (3rd option), it may be worth a try since all you need to supply is power and a motor. Nowhere can I find the current handling rating for this controller. It looks "light duty" to me.

John

- - - Updated - - -

Never mind the third option. It's only good for 0.5A.

John

- - - Updated - - -

Damn. Option 1 is NG either. Not for bipolar motors. I'll look some more for a simple OTS solution.

john
 
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