EEVblog Electronics Community Forum
Electronics => Projects, Designs, and Technical Stuff => Topic started by: nshin31302 on July 09, 2015, 06:12:20 pm
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So I built a slayer exciter tesla coil using this tutorial
https://www.youtube.com/watch?v=ioRBvUIrhqw (https://www.youtube.com/watch?v=ioRBvUIrhqw)
I made the secondary using some PVC and some magnet wire and bread boarded the circuit described in the video with the same component values except for using a TIP3055 instead of a MJE3055T. So the slayer exciter circuit worked perfectly on breadboard brightly lighting a CFL and drawing inch long arcs. So I decided to make the circuit more permanent by soldering it to a pad per hole style perfboard from RadioShack. After I was done, I tested it. The circuit on perfboard brightly lit a CFL and drew an inch long spark, but only for a few seconds. The arc length grew smaller and the CFL's brightness gradually diminished. I tried switching the primary coil's leads around, but I got the same result. What's wrong with the circuit? |O
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I'm guessing you've encountered a situation where the stray capacitance between the breadboard rows affects the circuit. As a test of this theory, looking at the pinout of the TIP3055, I would try adding (to your soldered prototype) about 3-5 pf between base and collector and collector and emitter and see what happens. If you don't have tiny capacitors like that, try making "gimmick capacitors" out of twisted pairs of wire maybe an inch or two long (insulated where they're touching).
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3055 is a hopeless transistor for high voltage, high frequency switching. If you must stick with a bipolar, perhaps try something that was intended for TV horizontal deflection.
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The original 2N3055 by Motorola had a transition frequency of 15 kHz. Maybe ti's TIP3055 is a bit different, anyways who did manufacture yours ?
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3055 is best left to the history books. Consider the datasheet spec: it's all about minimums. So you could get some slick-shit audio amp transistor with fT in the 10s of MHz, or some almost-germanium POS that's slow as molasses.
I suspect most are fallout from MJ15xxx production, or something like that: there's simply no fabs that old still around, making truly old shit. So whatever generic power transistor die doesn't meet spec for a higher valued product, is binned into the 3055's instead.
I'd much rather buy the properly spec'd part in the first place...
But anyway, there are better circuits to use for the present application, anyway, even among the overly simple (and dangerously fickle) types.
Tim