Best way to Drive Steppers?

[Peter Kiproff]

Is comparator switching, or resistor current limiting better?
I'm using Maxnc on some home brew stepping motors drivers for lathe & mill
work.
I've been satisfied that it works as well as it does however I'm seeing the
need for more speed/pwr

My setup is a Fet with a .1 ohm current detect applied to a comparator that
naturally oscillates @
approx 1 kHz, I adj the ref so I average 1.4 amp per phase as per mfg
recommendations.
My motors are rated 5V @ 1.4A, the raw pwr supply is approx 15 V, I'm
running half steps.
There are 4 per Axis X, Y, Z * 4 machines so I would like to modify what I
have.

The currant drops of if I try to go faster, so this is my limitation.
If I was to use say a 10 ohm 25 W resistor on each leg limiting the currant
to the same 1.4 A

Is it any better?

If I put a cap in parallel with each resistor would this improve
performance? what value?

Double the drive voltage? any currant derating?

Thank you for responding
Peter

 

[CFoley1064]

Subject: Best way to Drive Steppers?
From: "Peter Kiproff" peter@microtrendrobotics.ca
Date: 4/10/2004 11:36 PM Central Standard Time
Message-id: <g24ec.43602$wq4.2809992@news20.bellglobal.com

Is comparator switching, or resistor current limiting better?
I'm using Maxnc on some home brew stepping motors drivers for lathe & mill
work.
I've been satisfied that it works as well as it does however I'm seeing the
need for more speed/pwr

My setup is a Fet with a .1 ohm current detect applied to a comparator that
naturally oscillates @
approx 1 kHz, I adj the ref so I average 1.4 amp per phase as per mfg
recommendations.
My motors are rated 5V @ 1.4A, the raw pwr supply is approx 15 V, I'm
running half steps.
There are 4 per Axis X, Y, Z * 4 machines so I would like to modify what I
have.

The currant drops of if I try to go faster, so this is my limitation.
If I was to use say a 10 ohm 25 W resistor on each leg limiting the currant
to the same 1.4 A

Is it any better?

If I put a cap in parallel with each resistor would this improve
performance? what value?

Double the drive voltage? any currant derating?

Thank you for responding
Peter

A great tutorial on stepper motors is Jones on Stepping Motors. It's written
by Doug Jones of the University of Iowa Department of Computer Science.

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

It's a great newbie intro to the subject.

There are many ways to increase the power of a stepper motor. A lot of them
are covered in there.

Good luck
Chris

 

[John Jardine]

Peter Kiproff <peter@microtrendrobotics.ca> wrote in message
news:g24ec.43602$wq4.2809992@news20.bellglobal.com...

Is comparator switching, or resistor current limiting better?
I'm using Maxnc on some home brew stepping motors drivers for lathe & mill
work.
I've been satisfied that it works as well as it does however I'm seeing
the
need for more speed/pwr

My setup is a Fet with a .1 ohm current detect applied to a comparator
that
naturally oscillates @
approx 1 kHz, I adj the ref so I average 1.4 amp per phase as per mfg
recommendations.
My motors are rated 5V @ 1.4A, the raw pwr supply is approx 15 V, I'm
running half steps.
There are 4 per Axis X, Y, Z * 4 machines so I would like to modify what I
have.

The currant drops of if I try to go faster, so this is my limitation.
If I was to use say a 10 ohm 25 W resistor on each leg limiting the
currant
to the same 1.4 A

Is it any better?

If I put a cap in parallel with each resistor would this improve
performance? what value?

The added caps offer only limited benefit. (without a lot of work the sizes
have to be guessed at, anyway)

Double the drive voltage? any currant derating?

Thank you for responding
Peter

However you drive 'em the current always drops off the faster you go.
As you're using existing motors then the best option is to up the supply
voltage, (the motors won't be hurt). Keep the same limited 1.4A but use a
supply of say 30 to 50V. Expect the performance to increase pro-rata with
the supply voltage. This means big power resistors and heatsinks and a point
can be reached where it's cheaper to just use a high supply voltage and
bought-in chopper units.
regards
john