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[NEWBIE] Questions about flyback and 2n3055 circuits

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LAN_403

Unq104

Wed Aug 05 2009, 01:36PM

Registered Member #2264 Joined: Mon Aug 03 2009, 06:45PM
Location:
Posts: 1

Hello people.
Like many of you I happen have an interest for electronics and, recently for high voltage.
So I got my filthy hands on a flyback transformer scavenging it from an old monitor and got working on the driver circuit.

I made the single 3055 circuit on the wiki and, it worked. Somewhat.
The transistor heated up considerably even within 30 seconds of use. Not to mention that the arcs were really short (5-7 mm).

Then I tried the dual 3055, again looking at the wiki. Initially I didn't have much success.
I tried a lot of polarity combinations until I did what was basically two copies of the single transistor circuit. Two feedbacks, two primaries, two transistors, basically the same. Arcs are now 10-15 mm but still look quite weak.

Then I tried to make an improvised jacob's ladder. No luck with that. Although I can get 1 cm arcs, the jacobs ladder apparently doesn't want to start unless i put the two "corners" (closest points) under 4 mm of distance.
I tried:
- Bent clips (sandpapered)
- Wrapped Al-Foil
- 0.5 mm graphite leads
The leads seemed to work a little better but again since I can't bend them it gets a little problematic; and they also don't like to start an arc in the middle of them, just in the extremities.

So here are my questions:
Why the jacobs ladder gives so much trouble?
Why I get wimpy arcs?

I'd be tempted to also ask you why I had problems with the dual circuits, but unfortunately I can't attach a photo right now, i'll see what i can do.

My supply gives 8.5V and 5.65 amps. I once tried using another supply, with higher voltage but less amps (12v x 2.7 amps) I expected to get longer but thinner arcs but instead they're shorter. No idea why.
My resistances are about 27 ohms and 250 ohms.

Dr. Dark Current

Wed Aug 05 2009, 02:24PM

Registered Member #152 Joined: Sun Feb 12 2006, 03:36PM
Location: Czech Rep.
Posts: 3384

Hi, try this:

Zeus

Thu Oct 08 2009, 11:26PM

Registered Member #2316 Joined: Tue Aug 25 2009, 03:04AM
Location: Bendigo, Australia
Posts: 107

If you want more power try a car battery or go to instructables and search how to make a high voltage supply in
5 minutes. I don't have the URL.

Antonio

Fri Oct 09 2009, 01:11AM

Registered Member #834 Joined: Tue Jun 12 2007, 10:57PM
Location: Brazil
Posts: 644

Some facts:
The 3055 circuit is very, very bad. Without protections it will not last more than a few minutes.
Regular flyback transformers, intended to produce no more than 25 kV of output, will not produce sparks with much more than 1 cm.
Without current limiting, a flyback transformer producing arcs will not last.

Dr. Dark Current

Fri Oct 09 2009, 10:13AM

Registered Member #152 Joined: Sun Feb 12 2006, 03:36PM
Location: Czech Rep.
Posts: 3384

Antonio wrote ...

Some facts:
The 3055 circuit is very, very bad. Without protections it will not last more than a few minutes.
Regular flyback transformers, intended to produce no more than 25 kV of output, will not produce sparks with much more than 1 cm.
Without current limiting, a flyback transformer producing arcs will not last.

I have to disagree here. Of course this depends on the part you get, but diode-split transformers can usually output up to 50kV without problems when driven with a flyback-type inverter. Most of my transformers go >60kV, and I have one or two which have no problems starting an arc at ~12cm (~100kV). These diode-split transformers are quite limited in power however, and will not output much over 100W continouosly without overheating.

On the other hand, unrectified transformers from older B/W sets usually get fried at ~30-50kV, but can sometimes put out over 200-300W continuously (which is over 500VA) when driven from bridge inverter.

I had a Jacob's ladder on demo which ran over 5 hours with a transformer from B/W tv and the input power peaked at 400-500W (~1000VA).

Of course, you must know how to drive each type of transformer efficiently and how to get more voltage/power from them without damaging them.

quicksilver

Fri Oct 09 2009, 01:56PM

Registered Member #1408 Joined: Fri Mar 21 2008, 03:49PM
Location: Oracle, AZ
Posts: 679

Dr. Kilovolt wrote ...

Hi, try this:

[Aside from the ZVS driver and a ps with fairly high current range] the above driver is (IMO) one of the best for the broadest variety of flybacks. Transistors that have paid off were the TO3 2N3773 and the T220 mje19003. The non-polarized cap at the power supply end is critical:.However the unit.... IS VERY IMPRESSIVE. Ive built these and ZVS drivers and for a ps with 12v 3A -> this one appears to be a more flexible unit than the zvs. It's really a damn good driver design but does need a quality heat sink. Make both resistors 5w as they will heat pretty significantly during operation also.

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