Re: Basic Stamp Controlled Spark Gap

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

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

Hi Jeremy,

Please disregard my last post and this idea.  I went back and checked and I 
am not sure what the old VI scope picture was.  I redid the test with my 
big gap motor (1/4 HP 1800 RPM 10 inch disk):

http://hot-streamer-dot-com/temp/030513-01.jpg

I used much more trustworthy stuff to measure V and I:

http://hot-streamer-dot-com/temp/030513-02.jpg

This is the motor at start up:

http://hot-streamer-dot-com/temp/030513-03.gif

Kind of neet!  For the first second while it is spinning up it draws 30+ 
amps!  This droops the voltage but it is still seeing over 100 peak watts 
during start up.  After the internal centrifugal switch opens, it settles 
down to this:

http://hot-streamer-dot-com/temp/030513-05.gif

The current is just a distorted sine wave.  "No" nice spikes to lock timing 
with!  I was bothered by the old waveform and was thinking something my be 
screwed, and something was...

If anyone is interested, here is a perhaps more clear view of the motor 
start up and run:

http://hot-streamer-dot-com/temp/030513-04.gif

And here is a big data file of the data too:

http://hot-streamer-dot-com/temp/030513-07.CSV

Cheers,

         Terry


At 09:37 PM 5/12/2003 -0700, you wrote:

>Wow that's interesting... looks like a spike from
>a triac turning on -- do you use the phase-angle
>approach method of controlling your motor speed?
>('light dimmer' method...)
>
>I thought about using the microcontroller to directly
>drive a triac. Would start by setting an output high,
>which turns on an opto-relay which turns a triac on.
>Another opto relay will be in series with the triac's
>main gates and when it turns off (AC crosses 0 into
>a new halfcycle), we wait a few milliseconds and turn
>it on again. That would probably reproduce the wave
>form you have. Infact, I bet if I replaced the
>RC network in a light dimmer circuit with a pulse
>that's just as wide as it's charge time I'll
>accomplish the same thing. The trick is starting the
>pulse a few ms after the AC crosses 0.
>
>The new basic stamps support 'interrupts', an
>interrupt could be hooked in to run everytime the
>AC line crosses 0, (a timing triac turns off) wait a
>variable # of microseconds, then set an output high
>(turn on load triac).
>
>So it theoretically could 'drive' the speed of the
>motor and it would know exactly how fast it's going
>without any mechanical sensors. (Would require some
>sort of calibration, linear testing etc...)
>
>The same type of 'timing' triac could easily be
>used across the tank capacitor's drain resistors.
>(Turns off -interrupts the stamp- whenever the
>capacitor dumps.)
>
>
>--- Tesla list <tesla-at-pupman-dot-com> wrote:
> > Original poster: "Terry Fritz" <teslalist-at-qwest-dot-net>
> >
> > Hi Jeremy,
> >
> > Check this scope capture of a sync motor's voltage
> > and current:
> >
> > http://hot-streamer-dot-com/TeslaCoils/Misc/SRSG-VI.gif
> >
> > Note the very sharp current spike.  If you could
> > pick of the motors current
> > and high pass filter and detect the spike, you know
> > where the rotor is at
> > ;-))  Might be very easy to do...
> >
> > I could re run this test on my two sync motors just
> > to double check and be
> > sure if you need.  I could also figure out where in
> > the dwell the spike is.
> >
> > Cheers,
> >
> >       Terry
> >
> >