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Ash Small

Sun Apr 05 2015, 11:12PM

Registered Member #3414 Joined: Sun Nov 14 2010, 05:05PM
Location: UK
Posts: 4245

The 2N3055 does need a big heatsink.

I'll post some pics of some of my heatsinks tomorrow.

I think what's required here is a TO220 or TO247 package that can be bolted to, say, a CPU heatsink (if you tap and drill a hole), or some similar solution.

Gregary Boyles

Mon Apr 06 2015, 04:23PM

Registered Member #9039 Joined: Wed Dec 26 2012, 03:31PM
Location: Epping, Victoria, Australia
Posts: 117

Try this driver circuit by Steve Ward:

If you are using a battery to power the thing then you don't need to bother with the bridge rectifier/transformer bit at the top.

And you can vary the 555 part to a stock standard extended duty cycle astable configuration and add audio modulation to it based on this circuit:

The part to the left of and including the BC549 transistor. It forms a class A amplifier that drives pin 5 of the 555 timer with an amplified audio signal from an ipod or what ever. The result will be that you will hear music emanating from the high voltage arc.

It is really cool - you should give it a try.

The first time I tried it, while I was learning, I just fed the audio signal directly into pin 5 with no amplification, but the sound from the arc tends to be faint. This above method gives a much stronger audio from the HV arc.

Also I did not use a half bridge the first time around which means you have add a snubber network to dampen the kick back from the primary coil. Which in turn means you waste a lot of power. I was also using the newer flybacks that have a rectifier in the high voltage output which means they wont work to well with a half bridge driver anyway.

But you can get flyback transformer from ebay that do not have rectificiers on their HV output and that will work with a half bridge driver:

Patrick

Mon Apr 06 2015, 10:01PM

Registered Member #2431 Joined: Tue Oct 13 2009, 09:47PM
Location: Chico, CA. USA
Posts: 5639

Maybe he should be using and iggie first? it wont require phasing, which is where hes stuck, i think. but its more complicated from the circuit point.

Thu Apr 09 2015, 06:58PM

Registered Member #54664 Joined:
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Posts: 0

For the third time I disassembled the circuit, replaced the transistor with a good one, reassembled the circuit, connected it and once again it didn't work. Furthermore, the new transistor broke too after this attempt. There *must* be something wrong with the circuit since it's damaging every transistor I try to use. I'm very annoyed. Unless I find what's wrong I'll give up.

Ash Small

Thu Apr 09 2015, 07:32PM

Registered Member #3414 Joined: Sun Nov 14 2010, 05:05PM
Location: UK
Posts: 4245

Have you tried a ten turn primary and four turn feedback winding?

Also, try adding a light bulb in series with the primary to limit current during testing.

mister_rf

Thu Apr 09 2015, 10:38PM

Registered Member #4465 Joined: Wed Apr 18 2012, 08:37AM
Location: Bucharest, Romania
Posts: 145

In my opinion you need to give more details of the various stages of circuit testing.
In that respect you need to provide some pictures of the complete circuit, all the wiring included, to help us to understand where may be the issues. Anyway, if you are using a powerful supply and thereâ€™s no current protection implemented in that power supply, you have a big chance to destroy more transistors. Read my above suggestion about such simple current limiter circuit to be used in your experiments.

Ash Small

Fri Apr 10 2015, 12:03AM

Registered Member #3414 Joined: Sun Nov 14 2010, 05:05PM
Location: UK
Posts: 4245

Personally, I think you probably need more turns on your primary, espacially if the ferrite has a smallish cross section.

As RF points out, some photo's of the whole setup would greatly assist us

teravolt

Fri Apr 10 2015, 01:17PM

Registered Member #195 Joined: Fri Feb 17 2006, 08:27PM
Location: Berkeley, ca.
Posts: 1111

hi jaggions when you get tired of building that circuit try this

Mazilli ZVS is the best. I just pined 3 good sites and there are others on google and youtube

Fri Apr 10 2015, 06:19PM

Registered Member #54664 Joined:
Location:
Posts: 0

These are some photos of the whole setup. I hope you can understand something out of it, since there are many cables crossing each other and it's quite messy. By the way, thank you all again for your help.

Ash Small

Sat Apr 11 2015, 09:33AM

Registered Member #3414 Joined: Sun Nov 14 2010, 05:05PM
Location: UK
Posts: 4245

Ok, I'll have a go.

It looks like it's wired up correctly. Heatsink is a bit small, so here is what I propose.

It's good practice to twist together (as far as possible) the two wires that go to the primary. The same for the two wires that go to the feedback winding, and the two wires from the power supply.

What power supply are you using?

It also helps to keep all wires as short as possible. (the above is to minimise EM interference)

I'm guessing that either the primary or feedback winding (or maybe both) are 'back to front' (it is important to get the primary the right way round when using a DC flyback)

I propose, for testing, that you obtain a 2 volt 21 watt brake light or indicator bulb from an auto supply shop or garage and wire this in series with the primary. This will limit current to less that 2 Amps, which should be safe, even with a small heatsink.

If the circuit is just switching the 2N3055 on, the bulb will be bright (as bright as if it were just connected directly accross the power supply), if the 2N3055 is not switching on, the bulb will be off.

If the circuit is oscillating correctly, the bulb will light up, but will not be any where near as bright as if it were 'on' properly.

If the circuit is wired wrongly, tjhe bulb will prevent the 2N3055 from blowing.

You can then re-arrange the connections to the primary and feedback winding in all four possible configurations, without risking blowing the 2N3055, untill the bulb lights, but not as brightly as if it were connected directly to the power supply.

When the bulb is lighting up, but not fully, the circuit will be correctly wired up.

If you have any further questions, don't hesitate to ask.

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