Re: Proximity sensor for RSG

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

Original poster: "Terry Fritz" <teslalist-at-qwest-dot-net>

Hi Marco,

Just a little laser pointer pen (or real diode laser and battery), a small 
mirror or foil chunk glued to the rotor, and a length of fiber optic cable 
going back to any sensor, and your all set.  Nothing can go wrong and it is 
totally isolated.  Be sure the color of the laser and the type of fiber you 
use are compatible.

I worry that the fancy proximity sensors and such would either be too slow 
or would not like being close to the rather extraordinary electrics going 
on near the gap.  Isolation is another concern.  You don't want the primary 
current finding it's way back.

Cheers,

         Terry

At 10:07 AM 3/20/2003 +0200, you wrote:
>Hello all,
>
>I would like to add to Thor's rotating spark gap a position sensor to
>know when the rotating electrodes face the fixed ones. I don't need to
>know the absolute position (degrees), just an digital signal is enough.
>I'll use that to synchronize the primary capacitor charge and to count
>the bang amount.
>
>The RSG features a 30 cm diameter rotor, with 12 rotating electrodes (2%
>thorium doped tungsten, 0.5" in diameter). The motor is a 2850 rpm,
>achieving a maximum bang-rate of 570 breaks/s. I calculated:
>
>- min. face time = 1.27/(PI*30*2850/60) = 0.28 ms
>- min. period = 1/570 = 1.75 ms
>
>I was thinking to detect the rotating electrode proximity or painted
>black spots on the rotor side. I don't want to drill holes or whatever
>to the rotor.
>
>I need help in choosing the right proximity sensor: capacitive,
>inductive or magnetic? What will work? Anybody with experience on this?
>
>Regards
>
>
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