Re: solid state magnifier...accidentally...cool!

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Original poster: "Mike Novak by way of Terry Fritz <twftesla-at-qwest-dot-net>" <acmnovak-at-msn-dot-com>

Hi Justin,
I've been messing with a 555 driven flyback circuit this week, myself. I was
reading the specs on 555s, and aparently, they can reach a maximum frequency
output of 500kHz!!! So I decided to exploit a circuit for plasma globe
purposes. I completely threw out the duty cycle pot on my circuit (as it
doesn't do much unless you use the dual pot and diode version- later maybe).
So I got mine running from 1kHz-347kHz...
Very interesting results! Plasma globes work better with high frequency,
while voltage has less effect than one might expect. I got a tiny (>3mm)
arc, but the streamers were much nicer than at the resonate frequency of the
flyback where the arcs were more commonly 10mm.
Like you noticed, current is strangely high. I used my circuit to melt
solder, and the arc itself was hot enough to start my workbench (at school
:-) on fire from 1/2" away (luckily the bench has enough soldering iron
burns to camoflauge the mark it left).
I'm planning on making a small maggie based on the flyback later this week
( using a 2N3055 -TO3 style- with some inventive cooling for operation at
higher power) Perhaps a pentium heatsink and fan might be in order :-))
Good luck with your testing, I'll post my results and I look forward to
hearing about yours also.

~

I've been off the coiling beat for quite some time now, but I can't quit
cold turkey ;-)
Ciao!
-Mike Novak




> I used the output of a 555 chip to drive the gate of an IRF540 MOSFET
> directly (pin 3 straight into the gate). The MOSFET is then driving a
small
> step-up transformer that I wound, using a core off of an old flyback
> transformer. It has about 12 primary turns and roughly 400 secondary
turns.
>
> The output of the transformer will arc about .05" through air off the ends
of
> copper wires.....I'm guessing maybe a kilovolt output. The current is huge
> though..........I don't want to even try guessing. It instantly melts,
then
> balls up the ends of the wire lol.
>
> I had the frequency pot's on the 555 set to about 15kHz. BUT ------- I
> couldn't hear anything when pulling arcs off the xfmr's output. I thought
> this was weird, since I know I can hear 15kHz.
>
> I hooked it to a scope, and it was 300kHz!!
>
> It was working, yes, but at a totally unexpected frequency. So I
> thought............hmmmmmmmmmm.....I'll base drive the bottom of a
secondary
> coil that resonates at that frequency.....and have a solid state
> magnifier!?!?!
>
> So I did. I base drove a secondary coil with the HV output of the
> transformer. The secondary is 2" x 12" wound with #37........a LOT of
turns.
> Unloaded, the coil resonates at 330kHz. Right at the frequency the circuit
> was putting out.
>
> There is definately a resonant rise of voltage at the top of the coil. It
> lights up flourescent bulbs about 3 feet away. 1/2" streamers to air off
the
> top wire......
>
> The input power from the supply is 12V -at- less than an amp. Ten watts!
>
> Anyway................that was weird (prob. not weird, I just don't
> understand).
>
> We all know the 555 chip is (generally) limited to frequencies under
100kHz.
> The output from the step-up xfmr I wound is very close to 300kHz, I
measured
> this using an oscilloscope.
>
> So what is happening? I'm guessing some spurious oscillation is at work
> here.....the frequency and duty cycle controls for the 555 are totally
> useless when the circuit is running.
>
> Is is so cool anyhow, I accidentally made a solid state magifier. WOW how
I
> can't wait to actually run power into this thing.....
>
> Thoughts anyone?
>
> Justin Hays
> KC5PNP
> G-3 #1150
> Email: pyrotrons-at-aol-dot-com
> Website: www.hvguy-dot-com
>
>
>
>