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ignition coil- Ac- DC

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Omicron

Sat Mar 11 2006, 09:18PM

Registered Member #131 Joined: Fri Feb 10 2006, 09:25PM
Location:
Posts: 185

Is it possible to take the output from an ignition coil and make it DC? I need the power to power a x-ray tube. And I know about the dangers of X-rays. It needs to be cheap and simple. Goggle had nothing on this.

...

Sat Mar 11 2006, 10:09PM

Registered Member #56 Joined: Thu Feb 09 2006, 05:02AM
Location: Southern Califorina, USA
Posts: 2445

are you sure you have enough power to run the tube?

In any case, yes you can rectify it. To do so requires a string of avalanche rated (preferably) high speed diodes like sf1600's or uf4007's. Just string enough up to have about 1.5x or 2x the voltage you are producing and put it on the output of the coil.

Marko

Sat Mar 11 2006, 10:17PM

Registered Member #89 Joined: Thu Feb 09 2006, 02:40PM
Location: Zadar, Croatia
Posts: 3145

Iggies usualy have few tens of W of output power and voltage hardly reaches more than few tens of kV in best situations.
With two of them maybe you could push about 100kV and power a small, really small tube.

Omicron

Sat Mar 11 2006, 10:59PM

Registered Member #131 Joined: Fri Feb 10 2006, 09:25PM
Location:
Posts: 185

They are very small tubes from United Nuclear and I can get tubes rated at 45,000 volts

from

Hears the coil: MSD Blaster ignition
coil. 45,000 volt.

I'm useing 2 of these. ... where to get the dieodes? and price? how many? has any body tried this?

vasil

Sat Mar 11 2006, 11:15PM

Registered Member #229 Joined: Tue Feb 21 2006, 07:33PM
Location: Romania
Posts: 506

Hey guys, what you think about this circuit?

http://www.geocities.com/gemaria_ro/icdimdc.html

The dimmer will work, because it will see an AC current, but the primary of the ignition coil will see only dimmed monoalternances. So I suppose that the output from the iggy will have a bigger alternance than the other, something similar with a HV DC output. This will eliminate the need for HV diodes on the output.

Marko

Sat Mar 11 2006, 11:21PM

Registered Member #89 Joined: Thu Feb 09 2006, 02:40PM
Location: Zadar, Croatia
Posts: 3145

Use about 100 series 1N4007s and bootle caps for filtering.
If soldering miles of diodes bores you you can try selenium rectifier (usually 15 -20kV few mA, couple of seriesed MO diodes or maybe vacuum HV diode for such small currents)

Problem is getting such high voltages, try dimmer + 2 coils, you must also insulate everything very well...

If you have DC flyback I think it could do, or 2 antiparalel, without problem.
I designed driver that gives about 35kV (single flyback) from 20V input, with little more you can get 40, 50 easily.
Just don't know are diodes going to withstand it.

Omicron

Sat Mar 11 2006, 11:30PM

Registered Member #131 Joined: Fri Feb 10 2006, 09:25PM
Location:
Posts: 185

Where do I get this stuff? Radio Shack? And I am on a budget you no.

Marko

Sat Mar 11 2006, 11:45PM

Registered Member #89 Joined: Thu Feb 09 2006, 02:40PM
Location: Zadar, Croatia
Posts: 3145

So I suppose that the output from the iggy will have a bigger alternance than the other, something similar with a HV DC output. This will eliminate the need for HV diodes on the output.

You can never get actual DC from any transformer secondary.
Rectifying primary seems rather funny, most probably that way you won't get any output at all.

Simon

Sun Mar 12 2006, 12:50AM

Registered Member #32 Joined: Sat Feb 04 2006, 08:58AM
Location: Australia
Posts: 549

Omicron wrote ...

Where do I get this stuff? Radio Shack? And I am on a budget you no.

It took me very little effort to find this. Please don't ask us to check the RadioShack catalogues for you.

Bear in mind that an ignition coil driven in the usual way will have a very large HV spike with one polarity and a much lower voltage output of the other polarity for the rest of the duty cycle. Exploiting this you don't always need to use diodes to rectify.

Steve Conner

Sun Mar 12 2006, 01:05AM

Registered Member #30 Joined: Fri Feb 03 2006, 10:52AM
Location: Glasgow, Scotland
Posts: 6706

The X-ray tube should act as a rectifier, so you shouldn't need any diodes, just connect one ignition coil to each end (being sure to get the polarities right) and stand well back

Selenium rectifiers can only stand 26v per junction if I remember right, so they'll surely be far more bulk and hassle than 1N4007s (800v)

If you're on a budget, aren't MSD Blasters a bit expensive? I thought they were special high performance coils for racing engines.

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