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Re: [TCML] Help with high school Tesla coil
You need to add a series reactor limiting the primary current to short
circuit max of 8-10 Amps ---- then you can trace your problem in real time
with a meter or scope.
Back in my TV/radio repair days it was standard to have a 200 watt light
bulb in a bench socket to do such "short-locating" work.
It's no fun under power as you have to keep replacing parts and or/
sometimes breakers that go bad. We used the light bulb idea after we blew a
few fuses.
Dr. Resonance
On Thu, Nov 12, 2009 at 4:20 PM, Arnold, Mike <
marnold@xxxxxxxxxxxxxxxxxxxxxxxx> wrote:
>
> When the on-time control is "off," or set slow, the circuit breaker still
> trips, without any sparks though. Cranking up the On-time gives a second or
> 2 of sparks. With the On-time up high, different patterns of noise and
> sparks occur when changing the BPS. Given your comments and the fact that I
> get sparks, it sounds like the problem lies in the control box. Right now,
> the coil is basically unusable since it only lasts for 1 second before
> tripping a circuit breaker.
>
> Could I swap out the "555" chip in the timer control box, if that is
> indeed what it is (I can't read the numbers on the chip in my box and it has
> 14 legs)? Or should I change something else like one of those resistors? I'm
> not too good with the schematics. In fact all this is a steep learning curve
> for me. My electronics experience is limited to changing the tubes on my
> Fender amp and I guess that pretty much dates me.
>
> thanks again for your advice -- I need it
>
> Mike
>
>
> -----Original Message-----
> From: tesla-bounces@xxxxxxxxxx on behalf of John Forcina
> Sent: Thu 11/12/2009 3:50 PM
> To: Tesla Coil Mailing List
> Subject: Re: [TCML] Help with high school Tesla coil
>
> >From those pictures of the driver it looks to be based off one of steve
> ward's early drsstc driver designs. I found this one here
> http://stevehv.4hv.org/DRSSTC1/DRSSTC1OCDsch.JPG matches yours pretty
> nicely. However the coil you have does not have the over current
> protection
> circuitry part of that schematic. Basically in simple terms, the "BPS"
> control on the remote control controls how many times per second the coil
> turns on and off so lets say you have it set for 400BPS then the coil is
> actually turning on and off 400 times per second. The "On-time" also known
> as duty cycle controls how long the coil is operating within your BPS
> control. For example if you are operating ast 400bps with a 200us On-time
> then the coil will turn on for 200us 400 times per second. I would set the
> On-time knob as low as possible (for now at least).
>
> On Wed, Nov 11, 2009 at 7:13 PM, Arnold, Mike <
> marnold@xxxxxxxxxxxxxxxxxxxxxxxx> wrote:
>
> >
> > Thanks for your help, John. I know the students enjoy the Tesla coil and
> > I want to get it working again. Some of the students even seem to
> > understand its mysteries :^)
> >
> > I've posted more images at http://collierhighschool.com/tesla/ If you
> > need closeups of specific components, I would be happy to take more
> > photos.
> >
> > I will try to get my hands on a scope, but I'm a little doubtful I will
> > be successful.
> >
> > I do still think it has something to do with the timer not shutting
> > off. It still fires sparks off. I've included a photo of the dial for
> > the timer and, when I turn the dial, it feels a little funky.
> >
> > I don't want to blow up expensive components in the process of trying to
> > fix it so I look forward to hearing your thoughts.
> >
> > thanks very much,
> >
> > Mike
> >
> > -----Original Message-----
> > From: tesla-bounces@xxxxxxxxxx on behalf of John Forcina
> > Sent: Wed 11/11/2009 1:18 PM
> > To: Tesla Coil Mailing List
> > Subject: Re: [TCML] Help with high school Tesla coil
> >
> > Hi, It looks like that is a drsstc and not a standard sstc. We are going
> > to
> > need some more info on your coil in order to help you. Can you post some
> > pictures of the driver board along with the H bridge board and the dials
> of
> > the remote control. Your problem could be a number of reasons but for
> now
> > im going to list some obvious ones. You might have your "ON" time or
> duty
> > cycle set very high meaning the coil will pull much more power then if
> it's
> > set to a low duty cycle and you risk blowing your igbt's. Another thing
> i
> > can think of is the shootthrough on your igbt gates causing one igbt to
> > turn
> > on before the other is completly shut off and this will act as a direct
> > short across your supply rails for a very short time. By any chance do
> you
> > have or does your school have a scope that you have access to because
> that
> > will make debugging much easier.
> >
> > John.
> >
> > On Wed, Nov 11, 2009 at 10:02 AM, Arnold, Mike <
> > marnold@xxxxxxxxxxxxxxxxxxxxxxxx> wrote:
> >
> > > Our school has a solid state Tesla coil. I am attempting to get it into
> > > working condition. It had a bad solder connection in the tuning remote
> > > control. I have repaired the bad connection.
> > >
> > > Now the coil will spark for 1 or 2 seconds and then it trips the 20amp
> > > circuit breaker. The coil only works (albeit briefly) if the burst rate
> > > is high and the timing is high. The power cable gets warm in those
> > > couple of seconds. (Not to influence responses, but I'm not positive
> > > that the timing is working. It seems like the sparks burst without
> pause
> > > -- da-da-da-da-da -- until the circuit breaks. I can definitely slow th
> > > e rate -- da----da----da-----da. I can see the pot for the timing and
> > > it looks like it might have some cold solder joints.)
> > >
> > > When hooked up by itself, the low voltage transformer that powers the
> > > control board does not blow the fuse.
> > >
> > > A photo of the board can be seen at
> > > http://collierhighschool.com/teslacoil/board.jpg and I can provide
> more
> > > photos if it helps.
> > >
> > > Any help would be appreciated.
> > >
> > > Thanks,
> > >
> > > Mike
> > > _______________________________________________
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> > >
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> >
> >
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> >
> >
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