RE: Variable Speed SRSG - OPTICAL ENCODERS

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

Original poster: "Jim Lux by way of Terry Fritz <teslalist-at-qwest-dot-net>" <jimlux-at-earthlink-dot-net>

Given the huge mechanical inertia of a rotary spark gap, and the fact that 
you're not putting step function loads on the motor, a 1 or 2 pulse/rev 
encoder is probably sufficient.

Cars use many more pulses/rev encoders for ignition timing because they 
have to deal with rapid engine acceleration and deceleration, and, keep the 
spark timing to within a degree or so.  In a rapid acceleration situation 
(gear shifting), the engine speed may change 2:1 in less than a second, 100 
RPS to 50 RPS (for example) gives 18000 deg/sec^2, so the time between 
sparks is changing pretty fast. You can't afford to wait the time for the 
crank to come back around (10 milliseconds).


At 11:29 AM 5/14/2003 -0600, you wrote:
>Original poster: "Mccauley, Daniel H by way of Terry Fritz 
><teslalist-at-qwest-dot-net>" <daniel.h.mccauley-at-lmco-dot-com>
>
>A variable speed SRSG isn't a synchronous spark gap anymore. Its an
>asynchronous rotary spark gap ARSG.
>
>Also, an optical encoder would probably work best for your application
>especially if its a feedback system.
>You can get optical encoders with up to 1000 lines of resolution per
>revolution.  This 1000 lines can be extended to quadrature operation to get
>a maximum of 4000 lines of revolution.  Most likely overkill, but a 100 or
>250 line encoder
>would work great for a feedback controlled system.  And they aren't that
>expensive either.  A fully assembly which can
>couple to the shaft is probably about $30.00 for the whole thing.
>USDigital-dot-com as them.
>
>The Captain