Re: Sync Motor Conversion

Tesla List wrote:
> Original Poster: Terry Fritz <twftesla-at-uswest-dot-net>

Yo Terry.  We seem to be on yet another problem together :-)

> Although not the greatest bit of Tesla coil technology.  I have a big *.gif
> file of a strobe disk below.  I find it very useful to print out on nice
> paper and stick to rotors.
> http://www.peakpeak-dot-com/~terryf/tesla/misc/strobe.gif
> Florescent lights give a very nice pattern.  However, it would be nice to
> have a fast, simple, cheap, etc. strobe light.  I was wondering if a MOV of
> about 160 volts breakdown and a current limiting resistor in series with a
> florescent or other gas tube simply run from the AC line would do the trick??

What makes the fluorescent lamp work poorly is the long glow time
constant of the phosphors.  What you need is a gas discharge tube
with no phosphor.  Here are some cheap approaches that I know to

*	Super-bright LED run on unfiltered rectified DC, preferably
half-wave rectified.  Don't try to use a white LED because, at least
in the case of the HP white LED, it contains a phosphor which has a
glow tail.

*	Bare bulb mercury vapor lamp.  The bare bulb (clear outer globe)
will work as a strobe.  It works best right after the lamp is turned
on before the tube gets hot and glows on its own.  A trick is to run
the lamp on a variac.  Get it lit on high voltage and then turn it
down to near the flicker point.  

*	Fluorescent lamp operated with an instant-on (single pin) ballast
with a diode in the lamp lead.  This puts the flicker rate at 60 hz
instead of 120 hz which gives the phosphor more time to decay.  If
the ballast misbehaves with the DC produced by the diode, rig up a
cap and reverse diode to conduct the reverse cycle, bypassing the
lamp.  This is a circuit similar to that used in microwave ovens.

*	Automotive timing light.  A trivially easy trigger for a timing
light with a clip-on (magnetic) trigger is to make 10 or so turns of
hookup wire, clamp them in the inductive pickup and drive the wire
from your variac.  Very carefully advance the variac until the light
starts flashing.  This will be a touchy adjustment, of course, since
the variac is effectively shorted.  Some of the better timing lights
have edge-detect circuitry  which requires a sharp waveform to
trigger.  In that event, clamp the pickup around a piece of GTO wire
and hook it up to your neon transformer along with a spark gap.  If
you already have a timing light, this is by far the best solution.

*	Neon tube.  Find a friendly local neonist :-) and get him to make
you a foot long hunk of clear red neon.  No other color is suitable
because the other colors use phosphors so you're right back with the
same problem as the fluorescent lamp.  The flicker will be the most
pronounced if you use a variac to turn down the NST voltage to just
above the tube ignition voltage.  With me, the cost of this will
range from the cost of materials (about $3) to my minimum bench
charge of $20, depending on whether that tube is going to be used to
strobe a sync motor for a tesla coil or is going under some kid's
low-rider :-)

*	If you have a spare C-note, Graingers sells the Amedek strobo-tach
built into a flashlight case.  Ain't no General Radio but it works
pretty well.

John De Armond
Neon John's Custom Neon
Cleveland, TN
"Bendin' Glass 'n Passin' Gas"