Motor Stepper Example

[Luciano]

0.007degrees per microstep

http://www.indoor.flyer.co.uk/stepperdriver.htm
http://www.allmotion.com/EZHR17ENDescription.htm

Luciano

[Melanie]

Very clever... using a standard four coil stepper too... must find out more how they've achieved this.

[Luciano]

A tutorial.

By Douglas W. Jones
THE UNIVERSITY OF IOWA
Department of Computer Science

Control of Stepping Motors

http://www.cs.uiowa.edu/~jones/step/index.html


Chapter 5:

Microstepping of Stepping Motors

http://www.cs.uiowa.edu/~jones/step/micro.html

* * *

Luciano

[hansknec]

You are trying to compare apples to oranges. Melanies code (or anybodys code) will only be able to get you to half step mode. That's the digital limit. Anybody who talks about microstepping is in reality using a stepper motor as a magnetic voice coil between steps. By varying the amount of current to one energized coil vs the other energized coil you can get the N-S poles of the rotor to line up anywhere between the two energized poles of the stator. This is analog circuitry which is often programmed using an 8-bit DAC and thats where the 256 number fits into the equation as a step size.

[magand]

I agree with hansknec.
I apologize for my english but..... is the stepper driver that give to the motor the right sequence for microsteps.
Trickle is to reproduce a sine wave using a current sensor on the motor phase and an AtoD converter (high number of bit = high number of microsteps).
Usually these devices are inside dedicated drivers for microsteps.
See ALLEGRO A3972 for 1/16 steps.
regards
andrea

[mslaney]

Get it?
On and off.... :-)

I'm having a problem...
In it's simplest form, would the following be a brute force method of driving a bi-polar motor?

(PIC 16F876)
(defines, includes, and OSC set....)
(tris a, b, and c set to 0)

speed var word
speed = 100 'just an arbitrary number - will eventually ramp up to max

Spin:
porta = %00000001
pause speed
porta = %00000100
pause speed
porta = %00000010
pause speed
porta = %00001000
pause speed
goto Spin


When testing this with LEDs, this seems to work fine - the LEDs flash separately. However, when I attach the motor, nothing moves and the LED's flash in pairs.

Pinout:
porta.0 -> IRL510 -> LED/CoilA
porta.1 -> IRL510 -> LED/CoilB
porta.2 -> IRL510 -> LED/CoilC
porta.3 -> IRL510 -> LED/CoilD

If it matters, it's a work project that is behind schedule. A quick answer would be truly appreciated. I might even send you a check for $5 USD!!! :-)
Is there a single IC like the UCN5804 but for bi-polar motors instead of unipolar?

[mslaney]

I guess what I 'm asking is....Do I need an H bridge or is it a function of the program?