Re: SRSG timing light

["Tesla list" <tesla-at-pupman-dot-com>]

Original poster: "Mike Novak by way of Terry Fritz <twftesla-at-qwest-dot-net>" <acmnovak-at-msn-dot-com>

Well, Even if CRTs can't be used, it's cool to have a transparent rotor so
you can see through the rotor. When there's a flourescant light behind it,
there's a nice sharp profile of the electrode.
Ciao!

-Mike


----- Original Message -----
From: Tesla list <tesla-at-pupman-dot-com>
To: <tesla-at-pupman-dot-com>
Sent: Saturday, August 11, 2001 1:40 PM
Subject: Re: SRSG timing light


> Original poster: "by way of Terry Fritz <twftesla-at-qwest-dot-net>"
<FutureT-at-aol-dot-com>
>
> All,
>
> The TV field scanning frequency is just under 60Hz, at 59.94Hz.
> It used to be exactly 60Hz in the old days of black and white TV.
> They changed the frequency when they added color because
> they needed a submultiple of the color subcarrier frequency to
> permit the color subcarrier frequency to better fit into the
> relatively "unused" frequency areas between the harmonics in
> the signal.  Because of all this, if a rotary sync gap is observed
> by TV picture light, the gap rotor pattern will appear to slowly
> rotate and will make a full rotation in about 16.6 seconds.
> (*correction, see my test below)
> Since the TV freq is slower than the AC freq, the pattern will
> rotate in the same direction as the motor rotation.
>
> So the answer is yes, a TV can be used to tell if a motor is
> locked, but you must take into account that the pattern will
> make a full rotation in 16.6 seconds in the direction of motor
> rotation.  (*correction, see my test below).
>
> *I got curious and did a test.  I just ran my sync gap in a dark
> room with the TV on, and the pattern rotated 1/4 of a turn in
> just about 8.3 seconds, which would be about 33.2 seconds
> for a full rotation.  So the pattern actually rotates twice as
> fast as I calced above.   Maybe it's
> because the TV frame RATE of 59.94 divided by 2, or 29.97Hz,
> is dominating the situation, and making the pattern appear
> to rotate twice as fast as expected from the faster FIELD rate.
> In any case, this test shows that the pattern will actually rotate
> one turn in 33.2 seconds when the motor is sync-locked, and
> observed with a TV as a stobe source.  The 33.2 seconds for
> one rotation may cause confusion and inaccuracy in determining
> if the motor is locked, so it's probably a lot better to use a
> fluorescent light.
>
> The pattern was kind of hard to see anyway.  It is much
> much easier to see the pattern by using a fluorescent light,
> and of course the pattern is rock-steady under fluorescent light.
>
> John Freau
>
>
>
>