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PICList Thread
'driving VCR motors'
1998\11\24@110308 by andrew abken

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       Hi piclisters


  I have a motor that I removed from a VCR. This motor was used to
drive a large diameter flywheel (2.4") with the read heads mounted
inside. I have never seen a motor like this before, it seems to be
wired like a stepping motor with about 5 phases, but the motor reaches
a much higher rpm than a stepping motor. I am looking for more
information on this type of motor. I would like to drive this with a
pic and some mosfets but I am not sure how.


   Thanks
      Andrew (spam_OUTkn6zaTakeThisOuTspamyahoo.com)
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1998\11\24@134945 by Andy Kunz

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>wired like a stepping motor with about 5 phases, but the motor reaches
>a much higher rpm than a stepping motor. I am looking for more
>information on this type of motor. I would like to drive this with a
>pic and some mosfets but I am not sure how.

Very simple.  This is a "brushless" motor.  You should be able to find
information on the basics to control it from a lot of sources on the web.
You may also be able to use standard stepper-motor logic wihtout a problem.

Andy


==================================================================
Andy Kunz - Statistical Research, Inc. - Westfield, New Jersey USA
==================================================================

1998\11\24@141149 by Peter L. Peres

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On Tue, 24 Nov 1998, Andy Kunz wrote:

> >wired like a stepping motor with about 5 phases, but the motor reaches
> >a much higher rpm than a stepping motor. I am looking for more
> >information on this type of motor. I would like to drive this with a
> >pic and some mosfets but I am not sure how.
>
> Very simple.  This is a "brushless" motor.  You should be able to find
> information on the basics to control it from a lot of sources on the web.
> You may also be able to use standard stepper-motor logic wihtout a problem.

Actually ALL VCR brushless motors are 3-phase, with some really oldies
being 2-phase. They do however have more than one coil per phase. The
reason is that the drive electronics are cheaper in sixies than in
eightsies, of course, not to mention pin counts on the drivers.

They can be driven with nearly everything, including selsine outputs
(rectified phases of course) and manual multipole switches but for speed
one must produce a sine waveform.

I used a specific driver chip from Sanyo to drive such a beast. I think it
was a LA1610 or 1620. The schematic is simple, I'll find it and post it if
required. It uses 3 phases and 3 Hall bridges. The driver is available as
a VCR spare part (or was) in onesies.

Peter

1998\11\24@142222 by Peter L. Peres

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Be careful, it may or may not be a motor and it may or may not have Hall
sensors for feedback. Drum motors were actually Foucault brakes once, with
a belt driving them through a slip clutch in old U-matci and VHS machines
at least (and also some Beta ?).

Then there were drum motors that were biphase motors (sin-cos) with no
feedback Hall sensors, then there were biphase and triphase motors with
Hall sensors, and then again triphase, without, which is the current level
for small camcorders and VCRs. VHS is usually still at the three phase and
three Hall bridge level.

You will need to identify the wires carefully and use some logic.
Triphases are star-wound (thus, four wires out), and biphases also have 4
wires out but the no. of coils does not divide by 3 and there are 2
separate coils accessible.

success !

Peter

1998\11\24@152518 by Mark Willis

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Bob Blick's "Propeller Clock" uses one of these, his web pages on this
are at http://www.bobblick.com/bob/projects/mclock.html, I imagine he
tells you how to spin that motor up at least, as that's how the clock
works <G>

 Mark, .....mwillisKILLspamspam@spam@nwlink.com

andrew abken wrote:
{Quote hidden}

1998\11\24@160204 by Toby Baumgartner

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Hello All,  I'm new to the Pic List, but have been into PICS for a few
years now.

The motors on Bob Blick's prop clock page are regular DC motors, Which he
modifies to generate power from.

I have a similar motor to the one your referring to.  I removed it from an
ancient, full size, 10 meg hard drive.   I haven't actually used it yet,
but you should be able measure the resistance between phases to find which
pairs go together, and then drive it like a stepper motor,  The motor I
have has a 13 wires coming out of it, As near as I have been able to tell,
5 wires are for the stepping motor part of it, and the other 8 are for the
encoder.

Good Luck,
Toby

{Quote hidden}

*************************************************************
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Westerville, OH 43081
Phone (740) 548-1720        FAX (740) 548-7812
Email: .....baumgartKILLspamspam.....westerville.tt.slb.com
*************************************************************

1998\11\25@014009 by Nigel Goodwin

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In message <EraseME19981124155134.6552.rocketmailspam_OUTspamTakeThisOuTsend106.yahoomail.com>,> andrew abken <kn6zaspamspam_OUTYAHOO.COM> writes
>        Hi piclisters
>
>
>   I have a motor that I removed from a VCR. This motor was used to
>drive a large diameter flywheel (2.4") with the read heads mounted
>inside. I have never seen a motor like this before, it seems to be
>wired like a stepping motor with about 5 phases, but the motor reaches
>a much higher rpm than a stepping motor. I am looking for more
>information on this type of motor. I would like to drive this with a
>pic and some mosfets but I am not sure how.

It's a hall effect motor, basically a DC brushless motor. Instead of
using brushes to switch the coils in sequence, the coils are sequenced
by the electronics from the position information provided by the hall
effect sensors.

You would have to build a fair bit of circuitry to drive it yourself, it
would be much easier to use the driver I/C from the VCR as well - these
usually have an analogue input which sets the speed of the motor, which
is fed from the servo output to maintain the speed and phase exactly.
--

Nigel.

       /--------------------------------------------------------------\
       | Nigel Goodwin   | Internet : @spam@nigelgKILLspamspamlpilsley.demon.co.uk     |
       | Lower Pilsley   | Web Page : http://www.lpilsley.demon.co.uk |
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       | England         |                                            |
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1998\11\25@091559 by mkeitz

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On Tue, 24 Nov 1998 12:56:10 -0500 Andy Kunz <KILLspammtdesignKILLspamspamFAST.NET> writes:
>>wired like a stepping motor with about 5 phases, but the motor
>reaches
>>a much higher rpm than a stepping motor. I am looking for more
>>information on this type of motor. I would like to drive this with a
>>pic and some mosfets but I am not sure how.
>
>Very simple.  This is a "brushless" motor.  You should be able to find
>information on the basics to control it from a lot of sources on the
>web.
>You may also be able to use standard stepper-motor logic wihtout a
>problem.

Usually the motor driver IC is on the board with the motor coils.  It
just needs power (usually 12V) and a DC control volatge that sets the
amount of power applied to the motor.  Two feedback signals are typically
supplied, one being N pulses per revolution (called FG, for Frequency
Generator), and one is one pulse per revolution (the PG, Pulse
Generator).  The rest of the VCR circuit would examine these signals and
close the loop to the control voltage.

If the VCR runs at all, it's usually worthwhile to examine the signals
to/from the motor board before removing it.


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