Re: Rotary Sync Gap

To: tesla-at-pupman-dot-com
Subject: Re: Rotary Sync Gap
From: Bert Hickman <bert.hickman-at-aquila-dot-com> (by way of Terry Fritz <terryf-at-verinet-dot-com>)
Date: Sun, 27 Sep 1998 18:53:22 -0600
Approved: terryf-at-verinet-dot-com

Tesla List wrote:
> 
> Original Poster: "Bill Noble" <william_b_noble-at-email.msn-dot-com>
> 
> If you get a cheap timing light, it will do the trick - not the expensive
> inductive ones, but the cheap neon ones.
> 
> <<<<Thanks Bill, The inductive lights need a sudden firing or pulse on the
> HV cable to trigger the flash tube so they are of no use.  The cheap neon
> lights probably just use resistors and such.  I should easily be able to
> hook it accross the gap and turn up the variac until it just lights the
> timing light.  Then the adjustment should be easy.  I will be very cautious
> of the HV present and probably dissassemble the light to insure myself of
> how it works and how safe it is in this non typical use.  I doubt if one
> would want to touch it with HV AC present :-) - Terry >>>>
> 
> SNIP...........
> >> >     I do have one question.  Is there a way to hook up a neon lamp,
> >high
> >> > brightness LED,  etc. to shine on the rotor to indicate were in the ac
> >> > cycle the rotor is at.  In other words, I am trying to get the gap
> >points
> >> > to line up at the peak of the AC cycle.  There must be some simple
> >device
> >> > to do this.  I do have a nice inductive timing light that may be a
> >> > possibility too.  With my voltage probe down I can't see the cap
> >voltage
> >> > directly.
> >> >
> >> >     Terry Fritz
> >> >
> >
> >

Terry,

Thought of this idea while coming home from a Hamfest this weekend.
There was a guy there selling red 5 mW solid-state laser/collimating
lens assemblies for $11.00 each. Alternatively, a cheap laser pointer
could also be sacrificed for the laser/lens assembly. 

A simple circuit could be made which sampled a fullwave rectified AC
signal off a filament transformer to one input of a comparator followed
by a monostable. The other input to the comparator would go to an
adjustable threshold voltage so that you could trigger a bright pulse of
light from the laser diode at any point on the AC waveform. The highly
collimated beam combined with a small pulse width off the mono should
provide what you need from virtually any distance from the rotary. 

-- Bert --