Small tesla coil (1sq ft
From: Jeff Corr [SMTP:corr-at-enid-dot-com]
Sent: Friday, June 19, 1998 12:23 AM
To: Tesla List
Subject: Re: Small tesla coil (1sq ft
Alot of nice ideas there, but in order to keep it small I had to settle for
homemade rolled poly cap... in order to make it small I had to keep the
from the trannies as low as possible, a 9kv being the choice. I'm just
a golf ball wrapped with foil for the toiroid, again to keep things small.
>Nice results on your small coil. Are you using a torus top load ?
>As you may be aware secondary discharges up to 4X sec winding length are
>reported. Achievable at optimized quench + field shaping using torus is
>I worked with a student at the Calif State Science Fair in 1990 to achieve
>Sec height sparks from a coil only 10" high. Key to optimum performance was
>submerging the PRI and SEC in mineral oil - radical, sometimes messy - but
>For less noisey dorm demos and messing around with new ideas:
>For your dorm room consider using an alternate DC excitation mode. i.e.
>replace the NST with a 13kV to 17kV flyback from a video monitor of TV set.
>your 9kV ac rms NST = ~13kV pk
>your cap rating = 12kV ac rms = ~ 17kV pk (so this is the DC level to shoot
>Note that when you use DC the discharge rate will be slower depending on
>flyback/diode current supply capability vs Cap size, anywhere from 1 (lg C)
>50 (sml C) per sec depending on Cap size (~.1 recommended).
>Note also that the Cap value when using DC may be arbitrarily increased for
>longer sparks at the cost of longer charge times assuming the gap can
>the higher peak current. I recommend .1uF to achieve longer length single
>power discharge bangs (I get 9" from my Portable Battery powered (12v.04A)
> 6" Sec with 1.25J -at- 5kVdc & .1 & a vacuum switch (NO noise - great quench)
> - mileage may vary in air, increased voltage should result in much longer
>sparks J=c*v*v/2). Going to higher voltage flybacks from color
>allows the use of smaller Cap values and less peak current for the gap to
>quench while dumping up to about 5J for really long single sparks. By the
>I've done this by sharing the flyback HV anode lead (alternate path out the
> of TV case) with the TV or monitor - nondestructively ! The CRT is just a
>glass Cap. I just unplug the filament socket to reduce HV current drain
>(maximize available current for tesla cap charging.
>Keep in touch from your dorm -at- UNofOK or ?
>Dale, Redondo Beach, Calif
>Date: 6/18/98 6:11 AM
>To: Dale Hall
>From: Tesla List
>From: Jeff Corr [SMTP:corr-at-enid-dot-com]
>Sent: Thursday, June 18, 1998 12:45 AM
>To: tesla list
>Subject: small tesla coil (1sq ft) findings
>Hello all... in order to have a tesla coil in my college
>dorm room next year :-) I had to construct a special one.
>It is mounted on a 12"x12" plywood section, the secondary being only
>The reason I post this here is I find it interesting this coil can produce
>12" long sparks, the length of the coil itself.
>Just thought that someone else might be interested in duplicating this
>coil as it is small enough to carry anywhere, and still performs verywell.
>Here are the specs :
>power level - 9kv, 30ma 270VA
>capactitor - .004uf , rated at around 12kv (physical dimensions 8" long, 3"
>primary - helical, 10 turns of #20 solid copper, turns 1/8th inch apart.
>secondary 1.5"x12", #32 copper enambled.
>Spark gap, single gap, half an inch apart.
>No safety gap, no chokes, just neon, primary, secondary, gap, and cap.
>Enid, OK 73703