Re: home brew tachometer

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

Original poster: "by way of Terry Fritz <twftesla-at-qwest-dot-net>" <Pyrotrons-at-aol-dot-com>

Hi Mark, all.

I suppose the light-beam reflecting from the disk onto a photodiode would 
work to make the pulses (for counting), but here is a better, easier way to 
do things. This method requires that your stationary electrodes protrude 
toward the disk a little ways, it also requires an oscilloscope.

Step 1: Coil a bunch of wire (20 turns or so, doesn't really matter) onto one 
of your stationary electrodes. Put a magnet on the stationary electrode 
somewhere. The coil will output a little pulse of voltage every time an 
electrode flies by. Put the coil's output on Channel 1 of a 'scope.

Step 2: Put channel 2 of the scope directly across the secondary of a small 
step-down transformer to get the main's waveform (or just stick it in the 
wall if you want......)

Step 3: Adjust things to put channel 1's waveform on top of Channel 2's. You 
can immediately see what's going on with your RSG this way. Instantly 
calculate BPS, RPM, and know if it's sync or not. If it's sync, both 
waveforms will stay at exactly the same place in relation to each other.

ALSO: another method to find out if your RSG is sync or not. If you don't 
have a scope, but DO have a light dimmer, ignition coil, and capacitor 
(triggered gap setup), then read below!

> Couldn't a simple dimmer circuit like the triggered
>  gap driver, be used to fire a camera flash lamp?

Yes, definately. Run the HV output of the coil through a flourescent bulb 
(brighter than a xenon flashlamp), I've tried it, it works great, although 
the phosphors in the bulb flouresce too long. This makes things look somewhat 
blurry, but does work. Our SRSG has 4 brass strips on the backside to connect 
the electrodes, the brass was a perfect square with the synched HV firing the 
lamp (easier to make than a "ring" around the edge since we had the brass 
strips on hand)

But I thought triggered gaps were supposed to replace sync RSG's......just 
kidding. The day you run 15kVA through a triggered gap is the day I throw 
(smash, hurl, burn) the rotary away. Rotaries are a major pain (pg-13 here) 
if you don't have access to a machine shop.

So BTW, what IS the maximum power anyone has ever put through a triggered 
static gap? Couple of kVA? I wonder at what point it's unable to quench. (I 
bet a powerful vacuum triggered gap would work well) 

Sometime this week I'll try a triggered static gap -at- 15kVA, this should be 
really interesting. Aron cut some 3.5" copper pipe sections out for a massive 
gap "just to see what happens"....I'll put the dimmer/ignition coil HV on it 
just for kicks too...)

Kinda along these lines (actually not really), I put my shop vac air hose up 
to the streamers of one of my smallish TC's..............it sucks them in and 
is kinda neat.

Take care, good luck with your gap's........

Justin Hays
KC5PNP
G-1 #1150
Email: pyrotrons-at-aol-dot-com
Website: www.hvguy-dot-com