Generating a High Voltage Pulse

Hi, Brick. If you can use 12V instead of 5V, you'll be able to do quite a few things with an automotive ignition coil (available at any junkyard).

As a new electronics student, you may want to take a look at some of the best hobbyist circuit collection sites if you're scrounging for ideas:

There are a lot of good ideas here (especially in the first site) for hobbyist circuits with ignition coils.

Good luck Chris

In fact, there's no reason an ignition coil wouldn't work with 5 volts input, producing 5/12 as much voltage, which might be enough.

As I recall, an ignition coil is a transformer with the 2 coils connected together at one end (so that it has only 3 terminals) and a very high step-up ratio.

Hi, MC. You're right -- the ignition coil *will* work with 5V, producing a lower output voltage.

However, some of the hobbyist circuits use power MOSFETs which need the higher gate voltage to turn on. I suppose the OP could substitute logic level power MOSFETs and make other changes in the circuits as needed, but I thought it might be easier for the OP just to use a 12V supply and go with the existing circuits.

Good luck Chris

Thanks guys. Those sites look like they have some fun projects on them and I'll try to check through them before I ask questions from now on. I saw the relevant circuits with the ignition coils too. This looks like a possibility to fall back on, but is there a smaller option? Is physically connecting two piezoelectric crystals a waste of time? It just seems so nice that it would be so tiny if it worked.

An ignition coil works more like an inductor than a transformer and you might get just as much spark energy from 5 volts as 12.

The stored energy is 1/2 LI^2 and the current rises as I =(E T ) /L So, if you apply half the voltage for twice the time, you get the same current and stored energy. So, a 12 volt coil will probably work on a 6 volt system, but the RPM would only be half as much for the same spark energy.

-Bill

Piezos work as well but they are only widely available for cigarette lighters (and only as long as smoking isn't banned everywhere...). However, they operate on mechanical stress which I guess you don't want here.

Smaller HV transformers: These can be found in little portable TVs. The ones with a "real" CRT that is the size of a postcard. Sometimes you can find little HV transformers from military surplus or in the starter circuitry of small oil and gas furnaces. Check a place that does maintenance on these, maybe they could save an old board they swapped. Of course, you can always wind you own but last time I did that I had blisters that hurt for days.

Regards, Joerg

Hello snipped-for-privacy@gmail.com,

Ever think of modding a old disposable camera flash? Its triggerable and has a low volt drive. Trying googling it.

On 3 May 2006 02:19:01 -0700, snipped-for-privacy@gmail.com Gave us:

A simple transformer (or even a large inductor) and a battery will work. When you apply the battery, a magnetic field is exhibited. It is a "standing field" (non-moving, no transformation). The HV occurs (on all windings) when you remove the battery and the field collapses back down into the core. It can be several thousand volts, and can even have a sharp kick current wise. In fact, this is how old automotive spark plugs were fired. Close points, coil is energized... open points, spark fires.

I even made a "Lie Detector" this way once. (I was the determining factor on truth or lie) (I liked shocking people). Tee Hee Hee!

On Wed, 3 May 2006 09:38:15 -0400, "mc" Gave us:

A typical 30,000 volt ignition coil will make well over 1000 Volts, even if only a D cell at 1.5 Volts is used.

Or just get a flash camera at a garage sale and take it apart for what you need.

Flash assemblies use an oscillator to create an intermediate voltage (usually 300-400V), That's the audible whine you hear as the flash is being charged up -- it works at a high audio frequency. The camera or strobe then uses a triggering transformer to create the arcover voltage (4KV) for the flash lamp when you press the button on the camera. Once the arc has been established, the 300-400V on the cap is discharged through the flash lamp, giving the energy for the intense flash.

If you want to roll your own, you'll find the transformer (and some flash lamps) on p.78 of the current Mouser catalog.

If you choose an appropriate small series resistance simulating the series impedance of the flash lamp, you should be able to get a great arc without burning out the trigger transformer. Don't run this without a small non-inductive resistor -- you *will* smoke the small trigger transformer.

You can google the circuit to get the 300V from the 5V supply.

Here's something to get you a start, that apparently works with a 9V battery:

Good luck Chris

easiest would be an automotive ignition coil, 5v in should get you much more than 1000V out. you'd need some sort of circuit to switch it on and off... to cause the spark...

:)

I saw a lighter that had a coil based ignitor, it used a 12V supply and small traansformer.

those piezos may not last long, but I've always had the plastiic mounting fail on me so I can't be sure.

helium-neon lasers need a high voltage to run, you may find something useful on a web-site that deals with lasers and hologtaphy, but these days I suspect most are using semiconductor lasers for that.

another option is the high voltage trasnsformer from an old CRT-based monitor or TV... Again it'll need some sort of switching typically thses have a three stage Cockroft-Walton multiplier built in (unless it's a extremely old TV)

Bye. Jasen