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Old 24th February 2011, 04:22 PM   #11
vasko is offline vasko  Czech Republic
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Edit: I found it,it's 3 turns.

I made it oscillating, but still it wont start lamp. It looks like I don't have enough turns in secondary, but I have bad experience when you start it without load it just cut through isolation and short-circuits it.

Ill try some faster transistors like BUxxx and see if it will glow on 3V.
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Old 24th February 2011, 04:38 PM   #12
Elvee is offline Elvee  Belgium
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BU-type transistor are unsuitable, they are high voltage devices and have a saturation voltage as poor as your darlingtons.
Even BDxxx would be preferable.
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Old 24th February 2011, 05:05 PM   #13
Elvee is offline Elvee  Belgium
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The Zetex circuit works perfectly, even with BD131 transistors.
The output voltage is 800V peak, which is probably insufficient for most tubes, but you can increase the number of secondary turns to 700 f.e. (you have to use a proper ballast capacitor in series).

Did you implement a correct airgap? Did you use the right value for C3?
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File Type: gif Royer3V.gif (40.4 KB, 87 views)
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Old 24th February 2011, 09:40 PM   #14
vasko is offline vasko  Czech Republic
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I made new transformer. Secondary with ~2500 turns now. Now it glows on 1.5V battery.

But there is not much power. I guess that on ~50 kHz transformer that size could give 30-40W instead 1.5A that I have on 3V now.

It seems like you can't have both. Safe start and power.
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Old 24th February 2011, 10:03 PM   #15
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Default TUbe driver

Hi vasko

elvee is right, Royer converters can run from 3V. I published a 6V, hot-cathode tube driver based on this (using Zetex transistors) in EPE magazine March 2008 which you could use as the basis for your design. It's not easy to upgrade this to 40W. Running at 12V will draw 3.5A or so and ifyou resonate the primary you will need very high current capacitors, or two 2A types in parallel. If you resonate the secondary the current burden is lower but you still need a capacitor with high dV/dt rating.
If you are using a hot cathode FT then use a separate starting arrangement (preheat).

FOr CCFL you need kV's - even more dangerous! Also, high voltage windings have to be done with care - as you found they can break if the insulation /winding is not right. I only managed it winding thin wire in individual layers with insulated (waxed) paper like the old days, not "piled" as most coils are currently.

cheers
John
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Old 25th February 2011, 07:30 AM   #16
Elvee is offline Elvee  Belgium
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Quote:
Originally Posted by vasko View Post
I made new transformer. Secondary with ~2500 turns now. Now it glows on 1.5V battery.

But there is not much power. I guess that on ~50 kHz transformer that size could give 30-40W instead 1.5A that I have on 3V now.

It seems like you can't have both. Safe start and power.
I suggested a 40% increase in the number of turns, you went for a five-fold increase!.
Sure, it will strike any tube at any supply voltage, but the current will be reduced in the same proportions.

You have to be reasonable, choose a number of turns that will comfortably trigger your tube, even at a reduced power supply, and then select a secondary ballast capacitor to adjust the power level.

And good, high current transistors like the ZTX are a must if you want high power at low voltages.
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Old 25th February 2011, 02:10 PM   #17
vasko is offline vasko  Czech Republic
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Is there some program for transformer calculation (fast transformer ~xxkHz) that I could use?

I'd use that in NI Multisim to see if it suits well.
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Old 25th February 2011, 02:18 PM   #18
vasko is offline vasko  Czech Republic
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Also I'm wondering if I could use 2 windings in secondary, one for start and another for powering? To put some small capacitance on ignition winding...I don't quite know how should that be...

I'll use ZTX753 or 2SA1315.
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Old 25th February 2011, 07:41 PM   #19
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SIMetrix now has a transformer model which you can select some pre-defined ferrite cores or put in manual data for core size. YOu can account for an air gap by changing the effective permeability.
But to choose the core size, check the size of wire needed for the current, etc, you may have to use standard transformer equations!
cheers
John
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Old 3rd April 2011, 12:52 AM   #20
vasko is offline vasko  Czech Republic
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Quote:
Originally Posted by john_ellis View Post
I published a 6V, hot-cathode tube driver based on this (using Zetex transistors) in EPE magazine March 2008

can someone give me link of this article?
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