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Small tesla coil (1sq ft
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From: Dale Hall [SMTP:Dale.Hall-at-trw-dot-com]
Sent: Tuesday, June 23, 1998 3:01 PM
To: Tesla List
Subject: RE>Small tesla coil (1sq ft
RE>Small tesla coil (1sq ft) findings
to Malcolm and all following,
For the AC powered case I agree with your ~100W, BUT not with DC power.....
My 6.25"x16" coil powered by 5kVdc flyback, 12v .04A consumes less ~1/2 watt
Cpri= .1uF gap=small vacuum switch. Low power trade = one 8-10" bang per sec.
(1.25J, a reliable power arc is produced at each gap firing with 8"x22" galvanized
torus using a protruding point to point ground) Ccharge 5kV*.25ma for 1s= 1.25J
Helical Pri=.125"x11" Cu tubing tap ~3.8 turns Lsec=15.7mH (#22awg HPT)
Ipri =~600 Apk ~260 kHz Iarc=~23 Apk ~2 Mhz (23A*(xL=26138) = ~601kV)
I'm sure it would work well with a 10" sec (maybe better). (<<<100W !)
Going to higher V flybacks for >1.25J/bang say up to 5J chg=20kV*.25ma for 1s
(use lower Cpri for less Ipkgap) will yield longer sparks at greater input energy
expenditure but still small compared to the AC input power case which generates
more sparks/sec at a cost of more average input power required.
to Jeff and all folowing,
Did you read my 6/18 posted 9:54 this topic reply incl: flyback usage ?
excerpt ...
(I get 9" from my Portable Battery powered (12v.04A)
6.25" 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). .........
The trick to using flybacks with batteries is efficient electronics driver design.
Most of the posted designs use a push pull cfg which draws amps at ~25v.
A single FET or bipolar drive like the one in my 5kV is most efficient. It should
be designed such that the idle current is very low but rises upon demand - like
when charging the primary CAP. The flyback driver I use came with it. I merely
stripped out the unneeded functions (extra voltages for the CRT) from a 1" video
camera B/W monitor. The idle current is ~36 ma (this could improved upon if
I ever get motivated) at 12v (was designed for ~9v, I push it - been using it that
for years). I use rechargable AA NiCads which are available up ~2200 mAH
capacities (2200/50=~44hr) or single use alkalines could extend that 2-3x.
As I mentioned in the previous post, the most economical and easiest way to
checkout the DC mode: find an old B/W TV or video monitor and tap into the
anode connection. I remove the CRT socket to kill filament power and the
current drawn by the e-beam to get every uA to charge Cpri. The normal HV
precautions should be taken so as to not cause the muscle contraction (i.e.
don't touch charged stuff, discharge before contacting, ). To measure the HVDC
I use a 1000:1 resistive divider (1V dmm scale = 1kV) 999M to 1.1M to plug
into a 10Meg DMM. The load on the HV is only 1ua per kV + isolates DMM.
Dale, Redondo Beach, Calif
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Date: 6/22/98 9:52 PM To: Dale Hall From: Tesla List
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From: Jeff Corr [SMTP:corr-at-enid-dot-com] Sent: Mon, June 22, 1998 1:13 AM
To: Tesla List Subject: Re: Small tesla coil (1sq ft) findings
Just for a small assumption... how many watts is a battery capable of
supplying... say a 9 volt battery. Perhaps 4 double "A" batteries...
I'm just wondering on the ability to produce a coil from a few small
batteries and a flyback transformer. Anyone ever tried this? A small
handheld coil would be neat.
>Hi Jeff,
>
>> From: Jeff Corr [SMTP:corr-at-enid-dot-com] Sent: Fri, June 19, 1998 12:25 AM
>> To: Tesla List Subject: Re: Small tesla coil (1sq ft) findings
>>
>> >This post makes me think it could be time to resurrect Robert
>> >Stephen's suggestion of a competition for small coils. I would
>> >definitely be a starter in the bang for buck stakes. Whatthinks?
>>
>> Sounds interesting. By "small coils" do you mean the primary and
>> secondary or the entire setup... with chokes, without, what?
>
>I guess I really mean lower power. One can't run 100W say into a 10"
>coil and expect any output because the voltage developed would be too
>low. Therefore one would want to use a small resonator with low
>capacitance. I'd just be interested to see what is possible with say,
>a primary energy fixed at some level and BPS unlimited. I think a lot
>could be learned from such an exercise. I recently got better than
>12" from a 5kV 30mA transformer. I didn't scope the BPS but it would
>have been around 100, certainly not more. Perhaps it's something I
>should pursue.
>
>Malcolm