Using Car coil transformer

[zexelon]

I am a n00b in the practicalities of this field and I am currently designing my first fusor.

I am currently thinking about the power supply and I was wondering if it is possible to use the coil out of a car motor. The coil that is used to drive the spark plugs that is. I read somewhere that these coils can provide any whare from 50-100 thousand volts.

The coil requires a pulsed current to work as it is esensialy just a transformer. My idea was to use a 555 timer circuit opperating at about 100khz to drive a fast switching 12 volt transistor (do they make ones capable of switching that fast?). This should provide the potential difference required, however it will unfortunately be a pulsed DC current.

How does pulsing affect the fusor performance? I am sure someone has tried this so any pointers would be helpfull.

Sincerely
Melvin

[Carl Willis]

Hi Melvin,

Since you are considering automotive ignition coils, I presume this will be a "demo" fusor rather than a neutron-producing device.

That said, an ignition coil is a very economical and not-particularly-dangerous high-voltage supply and a good place to start. There are many, many ideas out there for how to power them. One of my favorites--due to simplicity--is the "light dimmer" circuit: you get any cheapo triac light dimmer and just wire it in series with the coil primary, a moderately large capacitor such as a motor-start cap (few microfarad), and a 110V AC power cord. The dimmer is a duty-cycle limiting device that turns on for part of the AC wave, creating a harmonic-rich waveform that gets good sparks out of these coils without burning them up. Expect to lose a light dimmer every now and then. They are poorly snubbed but still probably more robust than anything you can throw together. If you blow dimmers routinely, or blow the coil itself, you need a smaller capacitor. One nice thing about this circuit, besides simplicity, is that you get real AC high voltage from the coil. This gives you the versatility to drive various kinds of doubling and rectifying circuits. If you just use an interrupted DC input (how the old Ruhmkorff coils worked), you essentially get an interrupted DC output with perhaps a little bit of ringing.

There are plenty of transistorized circuits out there for driving the coils using DC. A 555 timer would be a good source for the drive signal, as would a PWM chip. The 2N3055 has featured in these hobby circuits for decades, not because it's the best out there but because you can run down to any electronics parts shop and buy another sack of them cheaply after you burn out your first sack worth! 100kHz sounds too fast to me (not for the transistors, but for the coil). I think that would drive up core losses. Maybe 20 kHz tops?

-Carl

[Todd Massure]

There aren't a whole lot of readily available high voltage sources that will work for neutron producing fusors. While car coils, computer monitors etc. produce high voltages, they can't supply the current needed.
I suppose it might be possible to use a car coil to charge a pulse capacitor, but it would take a while to charge it up to where you would get enough current for a pulse. There has been some interesting experiments done with pulsing fusors, especially by Larry Leins, if you search for "pulse" lots will come up

Looks like Carl beat me by a couple of minutes, but I'll leave it anyway
-Todd

[apollo]

Looks like Carl beat me to this by a bit, but yes, an iginition coil is a great place to start. You can make a 200-300W power supply using a flyback with this circuit:
http://forum.4hv.org/index.php?board=18 ... eadid=1723
It's a ZVS flyback driver.

That said, this circuit is less complicated and more powerful. It also doesn't require great capacitors. 500W.
http://forum.4hv.org/index.php?board=18 ... 14;start=0

There's a tremendous amount of data on 4HV.org about ignition coil drivers. It's definitely worth a look around.

2X2 vacuum tubes will do pretty well as rectifiers, as will a large string of 1n4007 diodes, which is what I'm using now (snag 100 or 500 on eBay for a few dollars). I enclosed mine in a PVC pipe with a screw terminal on each end and it works pretty well.

The most difficult part is probably building the power supply for the ignition coil. I would probably aim for at least 10A at 24V depending on the transistors and other factors. A dual ignition coil setup might actually get you into the fusion range (albeit very little fusion), assuming it's 500W.

[ebeuerle]

A little off topic but does anyone know of a good ignition coil driver for 12v DC that can stay on for long period of time without burning up? I have had trouble finding something that is stable and long running. The key is it needs to run for a LONG time. Any help would be much appricated:)
-Eddie B.

[apollo]

I'd hope that you could drive most ignition coils for a long period of time... the ones in cars have pretty much a dead short (except for resistor wire and resistor plugs of course) across their secondaries for hours at a stretch. You're probably driving it too hard. What is your setup like?

[ebeuerle]

Liam,
It's definitely not a problem with the coil itself as more the driver circuit. I tried out the one from here:
www.geocities.com/CapeCanaveral/Lab/5322/coildrv.htm
But it burned out quickly after trying to run it for any extended period of time. I am not an expert at circuits(been a while since i have messed with one). I have finally found something that works decently - a car relay DPST that makes a spark on a regular basis but I know it will probably burn out shortly on long period of run time. If I can buy a circuit that will run for a long time I would prefer that as I am focused on another problem(just need the 10-12KV sparks for the project I am working on). I don't really have alot of time to devote to building and testing a circuit when the research has already been done:)
-Eddie B.

[Verp]

Being at a point in my fusion experiments where I have more free time than money, I have been looking up cheap sources of parts. http://www.sherco-auto.com/ has the “UC12 (D500) Universal 12 Volt “ on page http://www.sherco-auto.com/ignition.htm selling for $8.95, inexpensive enough that paralleling a few does not seem too extravagant.

Rod

[ebeuerle]

Hehe I got a couple of free coils from a next door neighbor that is building a race car. Now just need to find a reliable way to drive them:)
-Eddie b.

[Mike Veldman]

The easiest method for continuous drive I've used is an SCR lamp dimmer through a 4mfd motor run cap to the coil from the 125 volt 60 cycle AC line. The SCR lamp dimmer will give you 120 PPS to drive the coil, the cap will give isolation, current limiting and help turn the SCR off. With the right isolation you can use a television tripler or voltage multiplier after the coil.

I have an automotive coil driven this way set up as a jacobs ladder for demonstratiion. The wow factor is great for kids and adults alike.

mike

[ebeuerle]

Yeah I have read that SCRs are great but I am limited to 12-14V DC(from car battery). I have yet to find something that will work in driving the coil without having to hook up to car computer-i would like to have a standalone unit that could do it. I was thinking maybe an aftermarket ignition coil system like from MSD but not sure how they work-they may require some input from the computer.
-Eddie B.

[Mike Veldman]

I guess I'm a little fuzzy on your intended use for this coil. Driving the coil from battery voltage is no great feat, simply use a 555 to drive a power mosfet or suitable darlington and adjust the frequency of the oscillator for the spark you like. Simpler yet is to use a 12 volt relay with the contacts wired in series with the relay coil so the contacts make the relay act like a buzzer. Hook the other set of contacts to the automotive coil. I've done this many times to simulate "buzz coils" on my antique engines.

mike

[ebeuerle]

Mike,
Yeah you gave me the idea for the relay and it works great:) I am just concerned at how long it will last before I will need to buy another relay. I was under the impression that it would burn out using it in the 'buzzer' mode. If that's not the case then great!! Otherwise I need to find a more longlasting solution.
-Eddie B.

[Jon Rosenstiel]

Eddie,
Have you paralleled the relay contacts with a capacitor? Around .02uF, 600V.

Jon Rosenstiel

[Jon Rosenstiel]

Mike,
Geez, never thought I would run across another old engine nut on this list.

Jon Rosenstiel

[Verp]

Speaking of old engines (but not nearly as old as the ones with "buzz coils"!), I went looking for a cheap coil on Froogle a while back (http://froogle.google.com/frghp?hl=en&tab=wf&q=). I found the most inexpensive one listed was being sold as a replacement part for the Ford 8N tractor. I found the 8N has a number of fans that like to keep them running, so I posted to their board; http://www.ytmag.com/cgi-bin/viewit.cgi ... &th=492549

Rod

[Mike Veldman]

"Geez, never thought I would run across another old engine nut on this list."

It's worse than that, I also have an 8N tractor as is mentioned in the next post.

Mostly I have too many toys and too little time.

Amazing what mania we fellows share. Eh?

mike