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Re: Herrick's...Entertainment Machine

Original poster: "R.E.Burnett by way of Terry Fritz <twftesla-at-qwest-dot-net>" <R.E.Burnett-at-newcastle.ac.uk>

Hi Ken, all,

Excellent photos of the SSTC.  I particularly liked KCH_tcg2.jpg ;-))
It is clear that Solid State coils have "come of age" when you can get
sparks like that.

The sparks do appear very similar to those from a classic spark gap type
coil.  My SSTC seems to produce sparks which have less branches and are
more straight for some reason.  Also my SSTC tends to flash over to the
primary if I force it to break out from a smooth toroid.  Your single
primary turn would seem to eliminate this flashover problem ???

Thankyou for sharing these details with us.  I can see now how it is
difficult to re-configure the primary from the photo.  However, the entire
setup appears quite neat and portable as it is.

Did you design and build the switching current-sources yourself ???  I am
very much aware of the problem of just using a bridge rectifier to charge
the DC capacitors,  so I have been looking at a similar solution.

I look forward to the availability of your plans,  and will listen out for
future developments in this project.

					Big up the solid state crew... ;-)

							-Richie Burnett,
							(Newcastle, UK.)

> Original poster: "Kennan C Herrick by way of Terry Fritz
<twftesla-at-uswest-dot-net>" <kcha1-at-juno-dot-com>
> Finally I have .jpg images of my s.s. coil & am posting them to 
> http://hot-streamer-dot-com/temp/ 
> as KCH_tcg1.jpg and KCH_tcg2.jpg.
> Tcg2 is a bit of tongue-in-cheek (and thanks, ol' Nic, for your
> inspirational photo) but here's a bit (repeating somewhat from prior
> postings) about tcg1, "Herrick's Patented Solid-State Alternating-Current
> Thunder and Lightning Entertainment Machine":
> 1. Input, 117 VAC, 60 Hz, 0-1800 W.
> 2. Physical size, 2 ft. square x 5 ft. tall.
> 3. Primary design:
> 3.1 Two equivalent untuned electrical turns driven by power MOSFETs.
> 3.2 Present configuration, 24 pairs of 500 V, 85 A MOSFETs in a patented
> circuit (U.S. #6,069,413 which can be viewed at
> http://www.patents.ibm-dot-com/ ) delivering ~200 A current-bursts through
> the 2 equivalent primary turns. It can be more fully configured, with 36
> pairs, to deliver ~300 A. There are 6 pairs of MOSFETs plus associated
> energy-storage capacitors per (horizontal) printed circuit board. With
> each such board is associated an additional (vertical) circuit board
> holding the MOSFET drivers and an off-line switching-current-source to
> both charge the capacitors and keep mains current limited to a selected
> maximum.  Attempting to charge some 43,000 uF to 160V by merely throwing
> a switch is guaranteeing instant trouble every time.
> 4. Secondary design:
> 4.1 12.5" coil diameter x 36" height.
> 4.2 Twenty ga. wire space-wound. Q = 80-100 -at- ~140 KHz resonance with the
> toroid in place. Construction is: sonotube with Jasco Water-sealant II
> applied; then closely-wound with .06"-dia cotton twine; then .003"
> "Mil-grade" teflon over that; then the wire, wound in the groove formed
> by the twine; then 8 beads of "Q-dope" to hold the wire in place.
> 4.3 Toroid, 6" x 24" Landergren.
> 5. Features:
> 5.1 Highest voltage to ground ever present anywhere in the primary
> circuit, 160 V. Highest MOSFET turn-off transient, n.g.t. ~400 V.
> 5.2 Self-tuned: Secondary is the sole resonant element in a feedback
> oscillator incorporating the power MOSFETs. Always dynamically tuned.
> 5.3 Spark rate continuously variable from 1 per button-press to 20/sec or
> more depending on power-line current capability and spark duration.
> 5.4 Controlled via a small "wand" at the end of a 15 ft. cable. Wand
> incorporates a collapsible ground rod for optionally inducing sparks.
> 5.5 Spark length, ~3 ft.
> 5.6 Spark duration, ~7 ms, fully-on and also ~7 ms interrupted -at- 64
> cycles on, 64 cycles off, etc. Approx. 200 us secondary-voltage rise time
> to commencement of spark.
> 6. Dissemination of plans:
> 6.1 I plan to offer my construction plans for a few tens of dollars fee. 
> They comprise 7, 11" x 17" drawings and a 16-page description.  Anyone
> interested, please contact me off-List.  Although my primary scheme is
> U.S.-patented (as part of my "entertainment"), anyone in the U.S. may
> make 1 or more if not sold in commerce (and anyone else may, of course,
> make dozens and sell them for thousands...if they wish).
> In the tcg1 photo, 
> 1.  A 4x5 view camera was used with ASA ~60 film.  A normal tungsten-lit
> exposure with the coil off was followed by a 6-8 second time exposure
> with no light except for that of the sparks (and the same procedure
> used for tcg2; first me & the coil, then the coil & the sparks).
> 2.  The secondary just sits on the primary's wire-bundle, which is merely
> 18 ga. 2-conductor "speaker" wire and is formed to the ~12" diameter.  It
> is held in place with the 4 nylon-Velcro straps and a small centering
> disk affixed to its bottom cover.  It connects via a short cable with RCA
> plugs to the red box.
> 3.  All the MOSFETs stand upright and each has on it a copper-pipe
> heat-sink.
> 4.  All the circuit boards are designed so that 6 pairs may be arrayed
> within the 24" x 24" baseplate's "footprint".  I currently use 4 pairs.
> 5.  The big inductors (4 are currently used) are for the switching
> current-supplies.
> 6.  All the 5V electronics (some 9 garden-variety ICs, a few
> opto-isolators, associated components, etc.), the low-voltage power
> supplies and the single mains bridge rectifier for the 160V are within
> the red box.
> 7.  The rotary switch allows for monitoring of various voltages & signals
> via a BNC connector.
> As I've commented upon already, I believe that the reason s.s. sparks
> tend to be not so long as spark-gap-driven sparks relates to the slower
> voltage-rise capability of s.s. systems.  With the very fast rise
> available from spark-gap coils, air inertia "bottles up" the spark for a
> brief time during which the top electrode's voltage may rise considerably
> higher than it would otherwise.  Then, the higher charge acts to extend
> the spark's length beyond that which the electrode's effective radius
> would normally support.  I have reached that conclusion only after some 5
> years' worth of effort in developing my s.s. system.  But at 73, I'm not
> much bothered, happily, that my *bippy* may be shorter than someone
> else's *bippy*.
> Ken Herrick