[Prev][Next][Index][Thread]

RE: Tiny tesla...

Hi Ross, Ken and all safety conscious coilers !

I agree, AC Lines / Xfmrs represent the most significant danger in all
offline TC's.

The Secondary danger however, is a function of the repetition rate and
energy per bang.
Danger increases as the # joules per bang and with greater bangs per second.

I don't wish to make light of the need for safety when dealing with Sec
discharges, but,
The 12ma Ross quoted (& other values) usually refers to sustained ACrms/DC
current through the heart,
not low duty 10uS period of ~.1uS osc period with long 8333uS dormant period
of the TC secondary discharge.
Do an RMS integration/evaluation of the Spark current (the ~2-20 Mhz)
waveform for comparison.
Use Terry's FO probes, or a O'scope current probe around the ground return
path being arced to.

Current applied external to the body enters a complex network dividing down
the contact current,
to that part of the current through a critical path in the heart that is
relevant.

External application example:  (to serve as a rough order of magnitude
reference)
Defibrillators start at ~100 WattSecs (joules) and go up to ~500 WS to
resync faltering hearts.
A capacitor is charged to ~2kV? adj to control energy to be delivered in one
impulse to the chest.

Our Tank Caps would make very ineffective defib's ! too little energy in one
pulse !!
So we need to assess the increasing danger with dormant time between pulses
and repetition rate.

Inadvertent attachment to the AC line or Xfmr sec can easily end it all, 
  you're are hit 120 times per second with a peak high voltage with lethal
current*time product,
  which happens if you are unable to "let go in time" (the primary mortality
issue)
  for you, a family member or spectator (any of which is likely to end your
coiling endeavor forever)
  (Y2K safety hint: always coil w/a buddy)

*************************************8

Danger can be mitigated via a two simple constraints:

1.) Use manual individual Spark Control, Constraining maximum Bang rate to
~1 per sec.
    Malcom :) calls this the "single shot" mode (I don't know if his SShots
always use DC)

    This is the ideal "Safe" way to study TC basics and instrument TC
behavior.

    I have demonstrated equal performance 28" in 3rd coil
Magnifier/Resonator configuration.
    (6' separation, Single Shot mode)

2.) Use Battery power to provide HV DC via a flyback converter. This is easy
to do.
    I have achieved 28" (2.45J 7kVdc .1uF) maximum power arcs (glass/air
confinement interface)
    (for Sparks.jpg, email me private)
    and predict 42" (5J) with same Pri/Sec & gap and perhaps 63" (10J) 

For first timers (proof to parents, school admin, etc.),
I recommend my 2.5J battery powered Single Shot DC TC design as being safe
by design.

My present Battery operated design:
 12v Batt to dc-dc converter draws .2Apk exponentially decreasing to .04A in
~3 sec, ~1 Watt avg, 
 charging a .1uF cap (can be mylar, read cheap - low rep rate, unipolar
charging) to ~7Kvdc
    dc-dc converter is from Mitsubishi 1.5" video camera monitor electronics
less crt & 3 boards
 Sparks produced by squeezing an air bulb activated switch ~once every 3 sec
(time constant ~1sec)
   ~30mHy Sec #24 awg 6.25"x20" PVC, 
   ~6.7uHy Spiral Pri 1/4" Cu tubing,
    Jensen/Kilovac Vacuum relay spark gap. (effective life decreases w/use &
increased bang rate)
        vacuum + 'jog' activation results in near perfect Quench = max
performance, max len sparks
        (for TekScopeWaveforms.jpg, email me private)
    Toroid: 8"x24" galvanized duct (4 x 90 deg elbows)

The Pri and Sec are sized for easy later upgraded to 4' - 6' Sparks w/same
Pri/Sec.
   Upgrade by either:
      increase the DC-DC converter Iout capability (difficulty increases
with power) 
        to charge the same tank Cap faster, for >BPS to TBD limit w/Cap
dielectric upgrade
        or charge a smaller Cap faster, see where >Rep Rate begins to
produce Longer Sparks !
        Note: Greg Leyh's Electrum is a 130kW DC TC, ~50'(?)sparks full
power discharges
   or add a suitable AC front end to replace the DC starter approach plus:
        replace DC Cap with AC capable Cap, 
        add Xfmr/controller, 
        replace Vacuum relay w/suitable RSG (best) or RQ static gap 

***********************
Ken,
Where are you located ?
A TV flyback with output rectifier removed to produce AC rather than DC 
  makes a nice easy to make tiny "TC HV like" project.
  It's what drives the Plasma Globe, Lightning Storm, etc. (Radio Shack)
  Plans abound on the internet or
  Information Unlimited, sells kits "mini mite" $19.50 
  I have not seen/used this product, perhaps someone on the list has.
       http://www.amazing1-dot-com/tesla.htm 

  or They can be put together for close to nothing, 
     depending on your resourcefulness,
     i.e. scrounging ability, availability of old TV's,
          ham radio & electronic swapmeets.

Experiment with an auto ignition coil's HV output (from junk yard)
At 12v it packs a stronger punch but is easy to play with. 
  (w/400v cap discharge in oil, 5" arcs are possible! at much greater
difficulty)
  When  younger I took an ignition coil out of the casing
  added a vibrator interrupter to provide continuous arcs.
  I later used it to power my first TC.
  Today I'd use a 555 controller and IGBT to power switch the coil 
  and make variable the pulse width and frequency. 

Regards, 
Dale
Redondo Beach, Calif (~40 mi North of Ross)

-----Original Message-----
From: Tesla List [mailto:tesla-at-pupman-dot-com]
Sent: Thursday, December 16, 1999 3:45 PM
To: tesla-at-pupman-dot-com
Subject: RE: Tiny tesla...

Original Poster: "Ross Overstreet" <ross-o-at-mindspring-dot-com> 

Ken,
High voltage IS really THAT dangerous.  The low voltage (120VAC) that you
feed most Tesla PSUs may be even more dangerous than the HV.  The output of
a small TC may not be able to hurt you, but even the smallest primary
circuits, HV PSUs, or 120V shocks can kill you.  I know that it's a much
disputed figure, but I have heard that as little as 12ma from one hand to
the other has been know to stop hearts.

I think that anyone who is mature enough to study TCs and use the internet
could successfully build a safe coil.  I recently helped a local high school
kid build a coil capable of 4+ ft arcs.  I told his parents in the beginning
that this was dangerous (read, deadly), but then I explained and
demonstrated the safety precautions that I use when dealing with HV.

Where are you located?  Maybe you could get together with a local coiler and
play around with their gear until you build some experience.  When you can
demonstrate to your mom that you are informed, maybe she will loosen up a
bit.

Tesla coiling is an extreme sport - no getting around it!

Good Luck,
Ross Overstreet
Huntington Beach, CA

-----Original Message-----
From: Tesla List [mailto:tesla-at-pupman-dot-com]
Sent: Thursday, December 16, 1999 6:21 AM
To: tesla-at-pupman-dot-com
Subject: Tiny tesla...

Original Poster: Ken Randall <kcrandal-at-tusc-dot-net>

Hi, All

     I want to build a small tesla coil to show my mom that high voltage
isn't really
that dangerous.  Then i c can make a big coil without my mother thinking im
going to
be electrocuted.

    Would it be possible to build a tesla coil like 3 - 5 inches high?
Would this
theoretically cost less?  Would it be easier to build?