bipolar stepper control
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Posts: 46,084
I'm having trouble controlling a stepper with my stampII and I was
wondering if someone could help me out.
it's a 3V bipolar stepper that I'm trying to run from a L298 H bridge
and all I can get out of it is some vibrations, even if I set my step
time to 500ms
I've got one coil connected to outputs 1 and 2, and the other coil
connected to outputs 3 and 4. I had to ground the current sense pins on
the L298 to get it to work at all.
I've had a unipolar stepper working with this setup but never a bipolar.
is there something wrong with my setup, my sequencing, or is there a
problem trying to run the L298 at 3v? (I have the logic input connected
to 5v)
I'd appreciate any help you guys can provide.
thanks.
Jason Lavoie
wondering if someone could help me out.
it's a 3V bipolar stepper that I'm trying to run from a L298 H bridge
and all I can get out of it is some vibrations, even if I set my step
time to 500ms
I've got one coil connected to outputs 1 and 2, and the other coil
connected to outputs 3 and 4. I had to ground the current sense pins on
the L298 to get it to work at all.
I've had a unipolar stepper working with this setup but never a bipolar.
is there something wrong with my setup, my sequencing, or is there a
problem trying to run the L298 at 3v? (I have the logic input connected
to 5v)
I'd appreciate any help you guys can provide.
thanks.
Jason Lavoie
Comments
I just looked at the L298 data sheet, and several thoughts come to mind:
1) The bridge always drives with two transistors in series, and the spec
indicates that the total drop will be ~2V. If you are supplying it with
only 3V, this leaves only ~1V for the motor winding. Try running it with 5
or 6 volts.
2) The current sense pins must be grounded, either directly, or through a
low value current sense resistor. If a resistor is used, you need even more
supply voltage.
3) Pin 9 (Vref) should be connected to 5V.
4) Hopefully, you have the clamp diodes shown on the example circuits.
If this doesn't help, maybe the phase sequence is wrong.
Let us know how you make out,
Ray McArthur
Original Message
From: Jason Lavoie <jlavoie@e...>
To: <basicstamps@egroups.com>
Sent: Saturday, May 13, 2000 6:09 PM
Subject: [noparse][[/noparse]basicstamps] bipolar stepper control
> I'm having trouble controlling a stepper with my stampII and I was
> wondering if someone could help me out.
> it's a 3V bipolar stepper that I'm trying to run from a L298 H bridge
> and all I can get out of it is some vibrations, even if I set my step
> time to 500ms
> I've got one coil connected to outputs 1 and 2, and the other coil
> connected to outputs 3 and 4. I had to ground the current sense pins on
> the L298 to get it to work at all.
> I've had a unipolar stepper working with this setup but never a bipolar.
> is there something wrong with my setup, my sequencing, or is there a
> problem trying to run the L298 at 3v? (I have the logic input connected
> to 5v)
>
> I'd appreciate any help you guys can provide.
> thanks.
>
> Jason Lavoie
>
>
>
>
> Jason:
> I just looked at the L298 data sheet, and several thoughts come to mind:
>
> 1) The bridge always drives with two transistors in series, and the spec
> indicates that the total drop will be ~2V. If you are supplying it with
> only 3V, this leaves only ~1V for the motor winding. Try running it with 5
> or 6 volts.
>
although I was running it at 3v I was able to get the motor to turn by manually
connecting each input to ground in sequence (touching wires together) I will
bump it up to 5v though.
>
> 2) The current sense pins must be grounded, either directly, or through a
> low value current sense resistor. If a resistor is used, you need even more
> supply voltage.
>
yup, grounded.
>
> 3) Pin 9 (Vref) should be connected to 5V.
>
done.
>
> 4) Hopefully, you have the clamp diodes shown on the example circuits.
>
I haven't added the diodes yet, would this cause it not to work at all?
>
> If this doesn't help, maybe the phase sequence is wrong.
>
see answer to #1, I'm pretty sure I've got the sequence right. would it be a
different sequence than a uni-polar stepper? (excluding half-steps)
thanks, I'll see what happens.
Jason
Original Message
From: Jason Lavoie <jlavoie@e...>
To: <basicstamps@egroups.com>
Sent: Sunday, May 14, 2000 1:10 AM
Subject: Re: [noparse][[/noparse]basicstamps] bipolar stepper control
> I haven't added the diodes yet, would this cause it not to work at all?
>
** The lack of diodes shouldn't stop it from running, but it protects the
IC.
>
> see answer to #1, I'm pretty sure I've got the sequence right. would it be
a
> different sequence than a uni-polar stepper? (excluding half-steps)
** Don't know...will sketch it out, hopefully tomorrow.
Regards,
Ray McArthur
The chip may not last very long without the diodes. You can get a pretty
good spike when the magnetic flux in the coils collapse.
> see answer to #1, I'm pretty sure I've got the sequence right.
> would it be a
> different sequence than a uni-polar stepper? (excluding half-steps)
Here is the code I used in PICBasic Pro to drive a bipolar stepper through a
L293D. PORTA.0 & PORTA.1 were hooked to one bridge and PORTA.2 & PORTA.3
were hooked to the other. If you want to visualize the bits directly on the
coils the coils are hooked up as AaBb. I would just uncomment the half step
code and comment the full step stuff or visa versa. No real reason that the
For loop is decrementing. It would work as well the other direction except
the motor rotation would be reversed.
myLoop:
For i = 3 TO 0 STEP -1 'Full Step
' FOR i = 7 TO 0 STEP -1 'Half Step
LookUp i,[noparse][[/noparse]%1010,%0110,%0101,%1001],mystep 'Full Step
' LOOKUP i,[noparse][[/noparse]%1010,%1000,%1001,%0001,%0101,%0100,%0110,%0010],mystep 'Half
Step
PORTA = mystep
Pause mySpeed
Next i
GoTo myLoop
Hope that helps you and get those diodes in place before the chip goes pop.
Tim
[noparse][[/noparse]Denver, CO]
had something
that looked similar, but for some reason it wasn't working.
Jason Lavoie
> Here is the code I used in PICBasic Pro to drive a bipolar stepper through a
> L293D. PORTA.0 & PORTA.1 were hooked to one bridge and PORTA.2 & PORTA.3
> were hooked to the other. If you want to visualize the bits directly on the
> coils the coils are hooked up as AaBb. I would just uncomment the half step
> code and comment the full step stuff or visa versa. No real reason that the
> For loop is decrementing. It would work as well the other direction except
> the motor rotation would be reversed.
>
> myLoop:
> For i = 3 TO 0 STEP -1 'Full Step
> ' FOR i = 7 TO 0 STEP -1 'Half Step
> LookUp i,[noparse][[/noparse]%1010,%0110,%0101,%1001],mystep 'Full Step
> ' LOOKUP
i,[noparse][[/noparse]%1010,%1000,%1001,%0001,%0101,%0100,%0110,%0010],mystep 'Half
> Step
> PORTA = mystep
> Pause mySpeed
> Next i
> GoTo myLoop
>
> Hope that helps you and get those diodes in place before the chip goes pop.
>
> Tim
> [noparse][[/noparse]Denver, CO]
Information about stepper motors?
The right sequence (for all types: unipolar, bipolar, etc.) and information
about H-bridges (and protection diodes for your L298) are very very very
good explained at:
www.cs.uiowa.edu/~jones/step
Regards,
Ar
I agree, we use that site, along with one from Thompson/Airpax as excellent
references.
Ray
Original Message
From: Ar
I'm new to stamp world. I'm looking for code to drive a bipolar
(4 wire) size 17 stepper motor. I've gotten the code for a unipolar
motor, but a bipolar motor needs different sequencing.
Any help would be most appreciated!
Thank you and Happy Thanksgiving, U.S.A. [noparse]:)[/noparse]
Ron Yost
It goes through some experiments I did in learning how to drive Stepper
motors.
Right at the end is a bipolar example - easily converted for a
Microcontroller design.
http://www.lennard.net.nz click on circuit ideas, then stepper motor (down
the bottom of the links.
Ben Lennard
*ACSE, ACCE
*National Certificate in Electronic Engineering
*Diploma in Electronic and Software Engineering
"To the optimist, the glass is half full. To the pessimist, the glass is
half empty. To the engineer, the glass is twice as big as it needs to be."
No animals were harmed in the transmission of this email, although the
Dog next door is living on borrowed time, let me tell you! Those of you
with an overwhelming fear of the unknown will be gratified to learn that
there is no hidden message revealed by reading this warning backwards.
> From: Ron Yost <musik42@c...>
> Reply-To: basicstamps@yahoogroups.com
> Date: Wed, 27 Nov 2002 11:56:32 -0800
> To: basicstamps@yahoogroups.com
> Subject: [noparse][[/noparse]basicstamps] Bipolar stepper control
>
> Hi!
>
> I'm new to stamp world. I'm looking for code to drive a bipolar
> (4 wire) size 17 stepper motor. I've gotten the code for a unipolar
> motor, but a bipolar motor needs different sequencing.
>
> Any help would be most appreciated!
>
> Thank you and Happy Thanksgiving, U.S.A. [noparse]:)[/noparse]
>
> Ron Yost
>
>
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>
>Have a look at my web page on driving a stepper motor.
>
>It goes through some experiments I did in learning how to drive Stepper
>motors.
Thank you very much!!
I also found this one:
http://www.geocities.com/SiliconValley/Foothills/4312/html/BasicStamp/stepp
rog.txt
Hope this hasn't been posted here a zillion times already. [noparse]:)[/noparse]
Thanks, everyone.
Ron