I have acquired a flyback transformer from my brother's Broken TV, and I would like to know how to drive it with a VERY simple Circuit, preferably a 555 Timer. I understand the danger's involved, but nevertheless I would still like to complete this project. This is for personal entertainment, not for a class assignment or university. I know that a flyback transformer requires 12VDC pulsed at around 15khz or 25khz, but I don't know how I would build such a High Frequency circuit, since my hobby had consisted of playing with 555's and the occasional MOT fun.

Thanks

 

While Googling, I did find this circuit:



Should I hook it up as a regular 555 Timer in astable mode?

Is there anything else I should hook up to this to improve performance? For the MOSFET, could I use a IRF830?

I am going to try this right now, so anytime between now and well now would be good. Thanks

 

http://www.electronics-lab.com/proje...016/index.html . It worked for me.

Playing with a MOT is not a good idea at all. If you get a shock from a flyback you will be spooked but you will live to tell about it. With a MOT, you will not know what went wrong because you will be on the floor dead.

Good luck!

 

Wow thanks! do you still think that a IRF830 would be useable as the MOSFET?

Here's the website link too:
http://images.google.com/imgres?imgu...tbnw=129&prev=

I just read down and saw this one. I have all the parts, and it sounds better so I will be referring to this image now: (attachment, link wouldnt work )

Attached Images

ET_Flyback_MKII.1-full.jpg (24.0 KB, 25 views)

 

Yeah I think the IRF830 should work. It depends on how much power you are giving though, but it should be plenty fine for some long arcs

 

Hooray! Thats just what I wanted to hear

I will let you know how it worked here in about 1 hour

 

If you want easy, you can't beat this circuit! I have tried it, and it works very well.

Attached Images

flyback driver.gif (6.0 KB, 23 views)

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It worked amazingly well! I was so happy with the performance! I will post a picture later, but the IRF830 Exploded! I replaced it with a IRF540, but I put a ton of fans next to it, so it runs on the verge of too hot. I run it in 10 second bursts.

Thanks guys!

Whats a good Super MOSFET, that Has superior Heat Shedding and power ratings? AKA Voltage, Ampre, thanks.

 

How large a heatsink do you have it on?.

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Would that be Microwave Oven Transformer?

thanks,
Corey

 

It looks like Heatsink No 4. I found it in the TV my brother had. The screen was about 26 inches wide I would guess.

Yes, MOT Does stand for Microwave Oven Transformer.

Nigel Goodwin, I had it running for about 5 minutes straight, so that may also be the reason.

The IRF540 Limits the amount of power that the FT gets, to around 1 amp I Think? It runs nice and cool also, after fixing a few connections that were stray, and recoiling the Exposed Ferrite Core, I am now getting sparks in 1cm+ Lengths. I believe they are around 10kV? If I had more Amps running through the coil, could I get better sparks?

 

I am glad to hear it worked for you! On mine, I didn't have to worry about the FET heating too much because it was rated to 40 amps or so and it was on a massive heatsink. lol it was overkill. I did have to worry about the 10 ohm 10W snubber resistor heating. After about 30 seconds I could have cooked an egg on it.

The FET will limit the average power the transformer gets over time (by PWM), but it won't limit the instantaneous current. The amount of current that will be drawn will depend on your flyback and the voltage you are giving the primary. If you are running it at 12V, I would imagine it would be in between 1 and 2 amps. It also depends on what your supply is limited too. What are you using for the voltage supply for the FT?

To have longer sparks give it more voltage and current. I found that around 15-18V at 2.5A was relatively safe and produced inch long arcs. With 12V at 1A I would only get about a centimeter like you reported.

 

The IRF830 can pass only 4.5A. The IRF540 can pass 33A. A huge difference.
We don't know how much current the flyback draws. If it draws 10A then the IRF830 is in serious trouble and will get very hot. If it draws 20A then if the TRF830 is used you should run for cover.

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Thank you guys! So it appears that my choice of replacing the IRF830 with an IRF540 was a good choice (and my only choice).

As for pumping more current in, what should I use as a power supply? I was using a wimpy 1.5A 12V Wall Wart, but I want to give it a ton of power, around 30V with several amps. What is a good choice? (for a power supply)

Thank you, it has been a true pleasure!

EDIT: I have seen them turn a PC power supply into a 30V Power supply. How can I do this?

 

Most flyback driver circuits have a trimpot for frequency and a second trimpot for duty-cycle. If the duty-cycle is low then a huge current is for only a moment and the voltage produced by the flyback is very high but the average current heating the Mosfet and drawn from the supply is low.

So try adding a trimpot for reducing the duty-cycle and add a big capacitor across the little wall-wart's output to store enough power for those momentary high current pulses.

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