Class A Ignitron? What? I need help!
Devin Chalmers
Hello, electronics enthusiasts! I'm doing a project about electronics for
school. I found a really cool demonstration on the Internet that fits
perfectly with my subject. One problem: I have no idea what the things I
need are.
These are them:
I need a 60 micro-farad, 10 kV capacitor (I found one of those) w/charging
circut. I don't know what a charging circut is, where I can get one, or
how much one costs.
I also need a:
Class A Ignitron (whatever that is) or a Spark Gap Switch.
If anyone could help me out, I'd be greatly appreciative.
Thanx!
Devin C
dcha...@ptialaska.net
Harry H Conover
Devin Chalmers (dcha...@ptialaska.net) wrote:
: Hello, electronics enthusiasts! I'm doing a project about electronics for
Hi Devin,
If you don't know what a charging circuit is, or what an Ignitron
is, you're likely attempting a project that is a bit over your
head. I'd suggest you re-think your project selection.
A charging circuit is simply a voltage source with a current limiting
device (possibly a resistor) that is capable of charging your capacitor
to a defined voltage within a certain period of time. This should be
easy to design and build.
The ignitron will likely be your major problem. These are large, and
generally costly devices that function more or less like a gigantic
SCR. (If you have one available in your junk box, you're way ahead of
the game. Otherwise, prepare to spend $$$.) Realize that most
ignitrons are scaled to the power control needs of a locomitive,
arc furnace, or similar high-power application.
The ignitron is a three-terminal device that uses a pool of
mercury as its cathode, has an anode, and uses a trigger element to
create a spark to the mercury cathode. When the trigger sparks to
the mercury pool, the device conducts between the anode and cathode
and gates currents generally measured in the hundreds to thousands
of amps.
What is your demo supposed to be, a rail-gun or something like that?
Harry C.
John S. Freitag
Hi kids,
I'll second Harry C's view (hi Harry) that if you don't know what an
ignetron is don't fool with it. It is basically a high voltage-high current
siwtch. A triggered spark gap will perform a similar function and is used
for such things as rail guns or geophysical survey equipment (read large
sound sources) and the like.
They work the same way. Picture a couple of electrodes spereated just
enough to prevent a spontaneous spare discharge.. A small "tickler"
electrode is between them. If you cause a spark to jump from the tickler
with a automobile spark coil, or the like, you will sufficiently ionize the
gap to allow discharge of the main charge. It is a triggered switch. LOTS
of juice. Last one I used was on a 150 kJoule sparker system. 15,000 volts.
When it discharged a peak current of about 2,000 amperes flowed for about a
millisecond. It made the feed wires jump off a steel deck --- SERIOUS
current!!
Don't fiddle with it unless you are up to speed on all aspects of what you
are doing. Screw up and you are DEAD, DEAD,DEAD !!!!!!.
John Freitag
Pamela Hughes
Devin Chalmers wrote:
> Hello, electronics enthusiasts! I'm doing a project about electronics for
> school. I found a really cool demonstration on the Internet that fits
> perfectly with my subject. One problem: I have no idea what the things I
> need are.
> These are them:
>
> I need a 60 micro-farad, 10 kV capacitor (I found one of those) w/charging
> circut. I don't know what a charging circut is, where I can get one, or
> how much one costs.
>
Good grief... thats 3k joules... what do you need that kind of power for...
wire exploder, ruby laser (EG&G is the only one I know of that makes flash
tubes that could stand up to that), rail gun? You'd need a 7kv xformer and
some 20kv diodes, some really high voltage bleeder resistors (can't use
regular resistors since they'd likely arc at that voltage), but if you can't
figure that out, you shouldn't even attempt it... short something and they
might not even be able to find all of your corpse. Cap alone must cost a
pretty penny.
> I also need a:
>
> Class A Ignitron (whatever that is) or a Spark Gap Switch.
>
Spark gap switch is two metal ball bearings (generally about an inch in
diameter). They are each connected to a bolt to form a set of electrodes.
There is a third electrode in the form of a needle with the tip near the gap
between the ball bearings, which are adjusted so that everything is far enough
apart that nothing arcs. The needle electrode is connected to the same sort
of ciruit used to fire a flash (generally using a 6kv trigger x-former or
better). When that is fired, the needle causes local ionization in the air
around the tip which creates an ionization channel that starts the main arc
between the ball bearings. Only problem with them is they are loud, subject
to variation in the required separation due to humidity, emit ultraviolet and
ozone (so should be contained in some sort of plexiglass box). Thyratron,
ignatron, kyratron etc are commercial variations in hermetically sealed
containers... there are a few small ones but most are large, very expensive
industrial things (think I heard of small kyratrons being used in some copy
machine equipment and I know EG&G makes them too, but they're on the export
banned list and I doubt you'd be able to get one). Still, I suggest you take
an electronics course and read and UNDERSTAND all the safety precautions you
need to take with devices like these.... Lannini's "Build your own Laser,
Phaser, Ion Ray Gun & Ohter Working Space-Age Projects" and McComb's
"Gadgeteer's Goldmine" might be good places to start, as they give the details
on building things like this as well as the proper discharge rod you'll need
to use before you even get close to that cap. of yours. (personally, I think
some of those things are pretty neat so I read about them but no way do I want
to actually mess with them.... probably the echo of my father's voice in the
back of my head, telling me how a charged up picture tube will kill you when I
used to help him fix those old black and white TVs when I was little... even
scarier to realize they didn't even have color TVs back then <g>)
Eric Y. Chang
Devin Chalmers (dcha...@ptialaska.net) wrote:
: school. I found a really cool demonstration on the Internet that fits
^^^^^^^^^^^^^ what is the project.
: I need a 60 micro-farad, 10 kV capacitor (I found one of those) w/charging
^^^^^^^^^^^^^^ this is huge and will take some time to charge
Again, what is the project? Is this for real? Eric