Re: turn counters was Re: Sewing machine motor

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Original poster: "Gary Peterson by way of Terry Fritz <teslalist-at-qwest-dot-net>" <glpeterson-at-tfcbooks-dot-com>

I found a turn counter useful when mass producing small transformers for
solid-state high-frequency inverter ballasts.  The single-layer primary and
short secondary turns were counted.  The wire for the long secondary was
measured for length as it was being wound.  I did this by wrapping a single
loop of the wire around a 12" circumference Plexiglas pulley mounted on a
mechanical counter salvaged from an old tape recorder.

Gary Peterson
Twenty First Century Books
www.tfcbooks-dot-com


----- Original Message -----
From: "Tesla list" <tesla-at-pupman-dot-com>
To: <tesla-at-pupman-dot-com>
Sent: Monday, January 13, 2003 6:26 PM
Subject: turn counters was Re: Sewing machine motor


 >
 > Original poster: "Jim Lux by way of Terry Fritz <teslalist-at-qwest-dot-net>"
<jimlux-at-earthlink-dot-net>
 >
 > A couple of thoughts:
 > 1) There are cheap counters made for odometers on bicycles. Consumer
 > products, etc.
 > 2) Why would you want to count the number of turns, other than for
academic
 > interest? In general, once you've decided on a size of wire and
 > corresponding winding pitch, the length of the winding will tell you the
 > number of turns to within a few percent.  More to the point, I suspect
that
 > the inductance of the coil won't change very much if the number of turns
is
 > say, 5% different.
 >
 > Wheeler formula is r^2 *N^2/(9*r + 10*l).. yes, there's a N^2 dependency,
 > but, say you've got 1000 turns instead of the 1050 you planned on: a 5%
 > error in the number of turns (but radius and length stay the same)... The
 > inductance will be off by 10 percent...an amount easily accomodated in the
 > tuning process.
 >
 >
 > Of course, having a turns counter makes it easy to calibrate your TPI on
 > the first couple inches, before you fininsh winding all 60" of the coil,
or
 > whatever.
 >
 >
 >
 > At 11:07 AM 1/13/2003 -0700, you wrote:
 > >I use a magnetic reed switch to trigger my electromechanical counter.
This
 > >involves mounting a permanent magnet on one of the winder's form
end-pieces.
 > >
 > >
 > > > Secondly, I also purchased a resettable electromechanical counter to
keep
 > > > track of form revolutions.  Anyone have any hints for me?
 >
 >
 >
 >