Re: Basic Stamp Controlled Spark Gap

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

Original poster: "Crow Leader by way of Terry Fritz <teslalist-at-qwest-dot-net>" <tesla-at-lists.symmetric-dot-net>

I've made ghetto sensors by wrapping like 50 turns of magnet wire around a
regular 1/4" bolt and taping a magnet to whatever is spinning. It actually
costs, nothing.I don't have any waveforms here, but the pulses were pretty
fast and clean, and of a upto a few volts.


KEN

----- Original Message -----
From: "Tesla list" <tesla-at-pupman-dot-com>
To: <tesla-at-pupman-dot-com>
Sent: Tuesday, May 13, 2003 6:38 PM
Subject: Re: Basic Stamp Controlled Spark Gap


 > Original poster: "Ben McMillen by way of Terry Fritz
<teslalist-at-qwest-dot-net>" <spoonman534-at-yahoo-dot-com>
 >
 > Hi Jeremy, Terry,
 >     Why not use a hall effect sensor? I realize that the
 > fields we're dealing with here are quite strong, but if you
 > were to find a sensor that was tolerant of background EM
 > fields (of the tesla coil type) and use a small neodymium
 > magnet to get rotor position, you'd essentially have your
 > 'spike' to feed back into the MCU.. The idea here being
 > that the sensor would only give a 'strong' output when the
 > magnet passed by.. If you had a strong enough (and small
 > enough) magnet, and a bit of epoxy..
 >
 >     I have no idea how feasable this is, or even if those
 > kind of hall effect sensors exist.. Tesla coil fields may
 > every well fry one on the first try..
 >
 >
 > Coiling In Pittsburgh
 > Ben McMillen
 >
 >
 > --- Tesla list <tesla-at-pupman-dot-com> wrote:
 >  > 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
 >  > > >
 >  > > >
 >  >
 >  >