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A small coil
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From: Dale Hall [SMTP:Dale.Hall-at-trw-dot-com]
Sent: Tuesday, March 03, 1998 3:58 PM
To: Tesla List
Subject: re: A small coil
re: A small coil
Hi All,
re: Richard Hulls mag and small coil listing, I thought members might be interested in one of my small coils.
For reasons of good control, low noise, control for electrical measurement and demos in the classroom, I've been using DC to excite my coils.
0.4 watt Pinput battery operated coil:
Spark gap: a vacuum gap (for good quench & low noise) SPDT (T shaped ~3"x2" T-R ?) which allows external mechanical common electrode positioning (metal diaphragm bonded to glass)
Presently I'm using a AAA Nicad powered flyback (~1" cube) extracted from a 1" video camera monitor. Removing extraneous circuitry results in 5kV Vout and 10v 35ma input. The current momentarily jumps to ~200ma for initial Cap charge (a few mS) then idles around 35ma. (driver redesign could reduce this further - maintains charge on resonator cap.) Sec is ~17mH 6.25x17" PVC eurathaned form #22awg hpt, Pri is ~3T of 0.125x12" Cu tubing using alligator clip for tap,
res cap = 0.1uF 5kV commercial mica ~3x2x0.3" rect (Custom Inc). Using 4ea 8"d 90 deg sheet metal heating duct toroid, produces 8-10" discharges at 1 to 2 per second. The gap is across the HV supply isolated by 2 mHy rfc's on both sides for isolation and power efficiency. Input current may be limited to a 40ma with little change in rep rate.
Dale
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From: richard hull [SMTP:rhull-at-richmond.infi-dot-net]
Sent: Sunday, March 01, 1998 7:49 AM
Subject: Magnifier #13 and a small coil.
... snip
MAGNIFIER #13 : Taking a short sabbatical from my ongoing fusor work...
A SMALL COIL:
I have long worked with efficient little two coil systems. I have demoed
them to the amusement and amazement of many at the Teslathons here. The
latest is based on just how much arc one can extract from a small amount of
energy.
The transformer used was a 3KV 30ma neon unit. I power factor optimized it
> note: 3kVrms*1.414= 4242Vpk
with a 1.2mfd capacitor when in operation. The capacitor in the tank was a
.0033ufd unit made up from three.01 2KVDC micamold capacitors in series.
The gap was a 12 gap series static gap with machine ground tungsten points
(.0125" diameter) set for .002" gap each. A Variac controlled the input
voltage. An AC RMS wattmeter (0-100 watts full scale) was hooked in the
circuit, but was read as volt-amps.
The primary was a coned archemedian spiral of flat band (aluminum), the
resonaotr was a 3"X7" tall unit wound with #28 wire. It resonated unloaded
at 800Khz. I loaded it with a 10"X3" spun aluminum toroid. the new
resonance was 510 Khz.
When tuned and fired in the circuit above, I got 7.8" of arc to a 2" round
grounded ball. This was with 48 volts in from the variac and the watt meter
read 28 VA. The secret was to take the variac up to where the gap fired
and then advance it to the point where I got the maximum number of firings
per half cycle (3-4), and no further. This occured at 48 volts into the
transformer primary.
Pretty stunning performance. I was able to light a neon tube of 3 feet
length over 4 feet away from the unbreaking out system. Fluoresent tubes
would stay lit a little bit farther away. This is the best small system I
have ever assembled.
Richard Hull, TCBOR