Re: Newbie with a Car Coil

["Tesla list" <tesla-at-pupman-dot-com>]

Original poster: "James Prior by way of Terry Fritz <twftesla-at-qwest-dot-net>" <james.prior-at-metrognome.demon.co.uk>

Hi Gary,

Thanks very much for the info. (Its your site I got the design from I 
think).
I've gone to a 5A fuse as suggested. 

I know this is dead basic stuff for you experts, but thought I'd 
include my own entry in the Pupman archives for any other UK 
newbie thinking of using a 240VAC dimmer + 12v car coil setup.

I've been running my (UK voltage) car coil jacobs ladder setup for a 
bit longer tonight, and the car coil got nice-n-warm, not hot after 
several short sessions of about 2-3 mins each, but after the longest 
session of about 4-5 minutes I thought "whats that smell?", and 
noticed the casing on my dimmer switch was looking positively 
droopy!!

I thought it was supposed to be rated at 700w but on closer 
inspection discovered its only a 400w dimmer. Maybe this 
contirbuted to the 3A fuse blowing?  So I'll upgrade my dimmer to a 
meatier one with a decent heatsink on the triac I think. In the 
meantime I've cut away some of the melted plastic surround from 
the dimmers components to allow better air circulation.

Onwards now - to start the tank circuit and coils.

Cheers
Jim

Date sent:      	Wed, 4 Sep 2002 14:46:46 -0700 (PDT)
From:           	Gregory Hunter <ghunter31014-at-yahoo-dot-com>
Subject:        	Re: Newbie with a Car Coil
To:             	james.prior-at-metrognome.demon.co.uk

> --- Tesla list <tesla-at-pupman-dot-com> wrote:
> > Original poster: "James Prior by way of Terry Fritz
> > <twftesla-at-qwest-dot-net>"
> > <james.prior-at-metrognome.demon.co.uk>
> > 
> > Hi Tesla group,
> > 
> > I've enjoyed reading and digesting the information
> > on various web 
> > sites, and the Tesla list over the last couple of
> > weeks since I've 
> > renewed my interest in Tesla Coils (actually my
> > interest was 
> > aroused again after a mention on the news about
> > recent anti-gravity 
> > work, which led to me re-investigating all this
> > amazing stuff on the 
> > internet).
> > 
> > When I was about 12 years old I built a TC, based
> > upon plans in a 
> > very old book called "The Science of Kinetic Art",
> > which explained 
> > how to build the coils and a Leyden Jar (a bottle
> > cap!). Luckily for 
> > naive me, in hindsight, it never worked very well,
> > otherwise I'm sure 
> > I would have killed myself!! ;-)
> > 
> > Anyways, I'm 40 now and I've started down the road
> > again, and 
> > have just built a basic car ignition coil power
> > supply and jacobs 
> > ladder based upon the  schematics on a couple of web
> > sites in the 
> > TC webring, with a view to bolting on the Tesla 
> > primary/secondary/SG and caps, etc.
> > 
> > The type of circuit I'm talking about can be found
> > at
> > http://hot-streamer-dot-com/greg/cararc.htm
> > Simple, quick-n-dirty. Mains into a light dimmer,
> > then cap, then 12v 
> > car coil (although I've built it with a bit more
> > care than just throwing 
> > together a couple of bits on a workbench that might
> > fall over - not 
> > that there's anything wrong with the basic approach
> > ;-).
> > 
> > I wonder if you'd mind me asking a couple of
> > questions, and I hope 
> > this isn't too basic or not quite "on topic" since
> > I'm only at the 
> > power stage!  So please bear in mind I'm an
> > experimental  
> > beginner, and my initial outlay will be basic/cheap
> > (but depends on 
> > peoples comments).
> > 
> > Being based in the UK, I'm on 240V AC, using a 700W
> > dimmer 
> > switch, a 12v car ignition coil and a 10uF 450v cap.
> > (I've also got a 
> > 3uF 450v cap which I started with and can parallel
> > with the 10uF for 
> > more umph). It all works quite nicely and produces a
> > good intense 
> > spark up to about 3 to 4cm. On the Jacobs ladder it
> > starts at 1cm 
> > going up to about 6cm where it breaks and with still
> > air it goes right 
> > to the top.
> > 
> > Now, the bit I'm interested in your thoughts on is
> > that the mains 
> > plug is protected with a 3A fuse, and when I run the
> > Jacobs ladder 
> > with the 10uF cap it will operate for about 10-20
> > seconds then 
> > blows the fuse. Surely this setup isn't drawing 3A x
> > 240v = 720W ?
> > Or is that quite feasible? I'm not sure what a 12v
> > coil driven at 240V 
> > through the cap will draw in terms of current, but
> > its got to be in 
> > excess of 3A to blow the fuse repeatedly. Thats
> > almost like a 1KW 
> > electric fire isn't it!  I'm just concerned about
> > the possibility of the 
> > ignition coil blowing up - is that likely? Will my
> > dimmer blow-up 
> > first?
> > 
> > Also I have linked the case of the car coil, and one
> > or two other 
> > metal parts (the caps are mounted on) to the earth
> > of the mains 
> > plug to give some basic safety protection of exposed
> > metal parts.  
> > At one point when I set the spark gap really wide,
> > the HT of the coil 
> > was finding these earthed parts instead of the -ve
> > side of the spark 
> > gap, and these "leak" sparks tracking across the
> > chipboard base 
> > were about 6 or 7cm long!! (not bad from a car coil
> > ?)
> > Well, I've insulated these to stop this now. 
> > Is this behaviour to be expected? i.e. a longer
> > spark to ground, 
> > than to the 240v negative.
> > 
> > The coil gets slightly warm after about 5-10
> > minutes, and on the 
> > web page it says it hardly gets warm even running
> > all day (at 110v), 
> > but I am running at double the voltage in UK. 
> > 
> > It seems there are differing opinions that this 240v
> > into a car coil 
> > can run a TC, but that an NST is more effective.
> > Why? Aren't both 
> > an ignition coil and an NST using 50/60Hz as their
> > frequency?  
> > Would it be better/safer to build a 12v driver using
> > a 555 timer IC 
> > and power transistor, thereby isolating the mains
> > supply, and also 
> > offering fine control over the characteristics of
> > the frequency and 
> > ratio.  
> > 
> > Where does the HIGH frequency so important to TC's
> > come from? 
> > Is it (depending on PSU) the 50Hz mains, the 555 or
> > the actual 
> > spark?
> > 
> > I guess my main concern is understanding whats safe
> > and whats 
> > not!  Am I being overly concerned about the mains
> > side when I 
> > should pay more respect for the HT side?
> > Is my 240v driven car coil going to give too much
> > current when an 
> > NST will be more refined?  Is it bad news to mix the
> > 240v mains too 
> > closely with a TC?
> > 
> > Finally - Is that too many questions in one mail?
> > 8-}
> > 
> > Would appreciate your advice.
> > 
> > Jim (being 12 again).
> > Smell that ozone.
> >
> -----------------------------------------------------------
> > James Prior

> Hi James,
> 
> There's no reason why you can't power a small Tesla
> coil with an ignition coil & dimmer. Here's a simple
> schematic.
> 
> http://bellsouthpwp-dot-net/g/c/gc31014/pulsebaby.gif
> 
> The high frequency results from the natural resonant
> frequency established by the tank capacitor and the
> primary coil. The spark gap behaves like a fast,
> high-voltage switch to alternately complete & disrupt
> the tank circuit current.
> 
> Your 10uF cap should only draw about 1.3A at 240vac.
> I'm not sure why your 3A fuse is blowing. My advice is
> to use a bigger fuse. Isn't 5A another standard UK
> size? I think all I ever used was 13A in my outlets so
> I wouldn't have to change fuses very often. All my
> outlets were wired through a modern GFCI breaker box,
> so I couldn't comprehend the British obsession with
> fuses (one in the outlet, another in the plug--plus a
> circuit breaker in the garage--what was all that
> about?). If the coil can be comfortably held in the
> hand without burning your skin, then the power level
> is probably safe. As long as the coil doesn't get hot
> enough to boil its dielectric oil, you are safe from
> bursting.
> 
> Best Regards,
> 
> 
> =====
> Gregory R. Hunter
> 
> http://hot-streamer-dot-com/greg
>