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'[EE]: Biploar Stepper Driver'
2001\01\04@073746 by David Duffy

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A question for anyone who uses stepper motors. (Roman ?)
Is there a good little driver IC for small bipolar steppers that
is not too dear & is available in Oz? The L293 looks OK apart
from the high quiescent current. I was thinking of using motors
stripped from 3.5" floppy drives. Still just mucking about with
different motors before I settle on a platform design. The guy
who does our metalwork will see some odd drawings come
through on his fax in the next week or two!  Everyone needs a
fun project every so often to keep them sane. :-)
Regards...
___________________________________________
David Duffy        Audio Visual Devices P/L
U8, 9-11 Trade St, Cleveland 4163 Australia
Ph: +61 7 38210362   Fax: +61 7 38210281
New Web: http://www.audiovisualdevices.com.au
New email: spam_OUTavdTakeThisOuTspamaudiovisualdevices.com.au
___________________________________________

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2001\01\04@075627 by Roman Black

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David Duffy wrote:
>
> A question for anyone who uses stepper motors. (Roman ?)
> Is there a good little driver IC for small bipolar steppers that
> is not too dear & is available in Oz? The L293 looks OK apart
> from the high quiescent current. I was thinking of using motors
> stripped from 3.5" floppy drives. Still just mucking about with
> different motors before I settle on a platform design. The guy
> who does our metalwork will see some odd drawings come
> through on his fax in the next week or two!  Everyone needs a
> fun project every so often to keep them sane. :-)
> Regards...

Hi David, the Mitsubishi M54646 looks nice, this
is $14 AU from WES. Drives both phases and only
needs two dig inputs for full bipolar operation.
It also has current ref inputs, so with two
analog pins (PIC pwm?) you can get full
bipolar microstepping from one 28 DIP chip
with only 4 PIC pins.

Second choice is Allegro TEA3717, it has 8 step
math-compensated microstepping built in with 3 bit
digital input, but you need two chips, one for
each phase. Can be sourced in Aust for about
$10 AU each.

Datasheets for both are common if you do net
search, or contact me off list I can email
datasheets to you. :o)
-Roman

PS. Is this for a little bot?

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2001\01\04@175306 by David Duffy

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Roman wrote:
{Quote hidden}

Thanks, found the data sheets easily.

>PS. Is this for a little bot?

Yes, but the unipolar steppers are looking much cheaper to drive.
5V steppers would be better as I already have 7.2V 1700mAH nicad.
The 5.25" FDD ones don't run very well from much less than 12V.
I might pull another couple of FDD's apart & see what drivers they use.
Regards...

___________________________________________
David Duffy        Audio Visual Devices P/L
U8, 9-11 Trade St, Cleveland 4163 Australia
Ph: +61 7 38210362   Fax: +61 7 38210281
New Web: http://www.audiovisualdevices.com.au
New email: .....avdKILLspamspam@spam@audiovisualdevices.com.au
___________________________________________

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2001\01\04@190717 by jb

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part 1 1062 bytes content-type:text/plain; (decoded 7bit)


> Yes, but the unipolar steppers are looking much cheaper to drive.
> 5V steppers would be better as I already have 7.2V 1700mAH nicad.
> The 5.25" FDD ones don't run very well from much less than 12V.
> I might pull another couple of FDD's apart & see what drivers they use.
> Regards...

I have taken those bipolar floppy steppers apart and tapped the wire that
connects the two coils on either side. In other words, there are four coils
internally, two sets of two. Each coil in a set is connected, usually by the
same enamel wire that the coil in comprised of. If you tap this connection
on each set, tie them together, then run out a fifth wire from that
junction, you now have a unipolar stepper rated at half the voltage (6V in
your case) and twice the current. You then need only figure out the step
sequence.

Diagram attached.

JB

PS. I have not had any mechanical failures doing this, but it may be
something worth considering if you don't think putting it back together will
go smoothly.


part 2 10527 bytes content-type:image/gif; (decode)


part 3 131 bytes
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2001\01\05@020138 by Roman Black

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David Duffy wrote:

> >PS. Is this for a little bot?
>
> Yes, but the unipolar steppers are looking much cheaper to drive.
> 5V steppers would be better as I already have 7.2V 1700mAH nicad.
> The 5.25" FDD ones don't run very well from much less than 12V.
> I might pull another couple of FDD's apart & see what drivers they use.

Ok, so now we're talking REALLY cheap? Try 4x BC337
transistor, as unipolar, they are about 20c AU each.
Or use a ULN2803A $5.95 AU at wes. This has 8
darlingtons in a 18 pin DIP and will drive two
unipolar motors up to about 500mA per phase.

I have done what you are doing, I think, see my
page at http://www.ezy.net.au/~fastvid/deskbot.htm
I used 2 x ULN2003A chips, as they only have 7
darlingtons in each chip. This was about the same
price as 1 ULN2803 but gives me another 6 outputs.

Probably would be wise to choose battery to suit
motors, if you want any power. The M54646 chip is
chopper constant current bipolar, and will give
41% more torque as it's bipolar, and will give
MUCH higher torque at speeds due to the chopper
system, and more efficient battery use. For the
extra $20 AU total I would go that way. :o)
-Roman

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2001\01\05@063742 by David Duffy

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>David Duffy wrote:
> > >PS. Is this for a little bot?
> >
> > Yes, but the unipolar steppers are looking much cheaper to drive.
> > 5V steppers would be better as I already have 7.2V 1700mAH nicad.
> > The 5.25" FDD ones don't run very well from much less than 12V.
> > I might pull another couple of FDD's apart & see what drivers they use.

Roman wrote:
>Ok, so now we're talking REALLY cheap? Try 4x BC337
>transistor, as unipolar, they are about 20c AU each.
>Or use a ULN2803A $5.95 AU at wes. This has 8
>darlingtons in a 18 pin DIP and will drive two
>unipolar motors up to about 500mA per phase.

Hi Roman, I think I didn't explain what I wanted to do!
I was looking for a cheap driver chip for bipolar steppers.

>I have done what you are doing, I think, see my
>page at http://www.ezy.net.au/~fastvid/deskbot.htm
>I used 2 x ULN2003A chips, as they only have 7
>darlingtons in each chip. This was about the same
>price as 1 ULN2803 but gives me another 6 outputs.

The UCN5821 is doing OK for the unipolar driver.
They are dirt cheap (about AU$2 each in tube lots)

>Probably would be wise to choose battery to suit
>motors, if you want any power. The M54646 chip is
>chopper constant current bipolar, and will give
>41% more torque as it's bipolar, and will give
>MUCH higher torque at speeds due to the chopper
>system, and more efficient battery use. For the
>extra $20 AU total I would go that way. :o)

You might be right about that - just didn't want to waste too
much money on the drive circuitry. I might just go & buy some
wheels & get the base plate made up next week. Then I can
muck about & see instead of just contemplating about it!
Regards...

___________________________________________
David Duffy        Audio Visual Devices P/L
U8, 9-11 Trade St, Cleveland 4163 Australia
Ph: +61 7 38210362   Fax: +61 7 38210281
New Web: http://www.audiovisualdevices.com.au
New email: .....avdKILLspamspam.....audiovisualdevices.com.au
___________________________________________

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