Troubling Flyback Transformer Pins

      I'd like to request someone to share their knowledge about their "flyback" knowledge or experiences with me since I'm having trouble finding the primary coil pins with my flyback transformer. I'm constructing my own HV power supply and I decided to go through this tutorial.

      I've read much on the web and found the 0v output pin of my flyback. The problem is .. I couldn't find the primary and secondary since I'm using an analog multimeter and the tutorials on the web are all digital..
      When I test the pins with my multimeter set to ohm range of x1, I do not get a pair of 1 ohm pins but instead I got the result of "Continuity" when I test on following pins, they seems to be connected but none of the pins show to 1 ohm.. and thus I've adjust the Ohm Adjustment.

The results are

Continuity 1 : 1,2,6,8
Continuity 2 : 3,4,7,10
No Continuity: 5,9

Pin no 5 is 0v output..  I've attached the pin number diagram at photos... my drawing and actual pins..

Have you got any idea to find out the primary coil?

I've also attach my driver from CFL..


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A flyback does not have any capacitors inside, so you don't need to discharge them.

Powered by 12V with a ZVS driver a flyback can draw up to 10 amp on the primary side, so considering the higher voltage a CFL of over 50W might work for the purpose but AFAIK not in a way that the flyback gives the full output voltage possible.

Consider the windings for your primary as a resistor, the more windings, the higher the resistance.

For the high frequencies used in a CFL driver you might have to find the right match in terms of turns on the primary coil and maybe even add a small capacitor in series to limit the current.

For fun might be ok to play with a flyback, as a power supply I would prefer a neon transformer or make my own multi stage power supply.

All depends on the power you need...

It is almost fruitless to find the right connection using a multimeter of any kind, better option is to check the circuit board where it came out.

There are several windings connected with diodes and potentiometers that will often fool you.

A much better option is to ignore all this and to add a new primary on the core of the flyback, 10 to 30 turns depending on input voltage and required output, play around with some turns and use what works best.

Be aware that modern flybacks only provide a DC output but no AC.

They are also quite fragile in terms of overvoltage.

If you try to make long arcs for example, every time the arc breaks the coil has to deal with all the energy that goes nowhere, sooner or later it will arc over inside the windings.

Output amps are also quite low and going over the rating of the flyback causes overheating.

Most CFL drivers use the heating filament in the CFL as a resistor for a diode/capacitor voltage doubler and to keep the frequency in specs.

Connecting a flyback directly on such a system does not always work as the circuit fails to swing.

Can make it out on your images but it seems there is a cap on the output, check if there is a diode too and where they connect to the little transformer - you want to connect directly to the transformer if the circuit fails to work in the standard configuration.

Also be awre that a 20W CFL can only deliver 20W!

As the output is around 400V without the cap and diode you are close to the orginal specs of the flyback but have to consider the different frequency.

The lower the frequency, the more stress on the flyback.

As a rule of tumb I say if you can hear the arc the frequency is too low.

For lower outputs a circuit from a disposable flash light camera works great, they produce around 300V from 1.5V and can be driven at up to 5V if you add a heatsink for the transistor, resulting in close to 1000V output.

(author)  Downunder35m2 years ago

Thanks for the info... but the arc haven't come out.. sorry for interrupting, but I think i'm missing out something and couldn't figure it out.Or did I made a mistake?

But the current is flowing until the end of the CFL driver... I'd wrapped up 18 turns on the flyback core and connected the power supply... Did I miss the 0v output pin or Do I need another component to produce arcs?


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I think it is a problem with the driver.

It works with the CFL as the right load and with the flyback on it it fails to swing properly.

You can try to add a small capacitor in series with the coil on the flyback,

start with 220nF and work your way down towards 10nF to check if you can make it work.

The load of the coil is much higher than the CFL.

Coil offers an inductivity while the CFL gives a capacity.

Can you measure a current going into your new coil?
If no current it usually means the CFL driver can't resonate and won't produce any output at all.

The ground pin for the high voltage can be found in a working setup by checking where the arc wants to go - usually it will be only one or two pins that give a good ground.

As we are dealing with quite high frequencies I also use a much thicker wire for the primary, at high frequencies the electricity tends to travel on the surface of the wire instead of going through the entire wire.
If you are after only high voltage, did you consider using a neon transformer instead?
More reliable and they have no problems if there is a short or no load attached.

(author)  Downunder35m2 years ago
Today, I removed the CFL driver and used the circuit from the bug zapper instead and it really works... which shoots about 2cm arcs from the flyback.. Thanks for your help. Now I can use it to supply high voltage power to my other projects.

You are welcome!
In case you need a higher output check ZVS drivers for the flyback ;)

(author)  Downunder35m2 years ago

Here's my working thingie... which only needs a little modification... but since I'm using the rechargeable battery(the small un-descripted one from the photo) from the zapper, the lifetime is too short.Is there a way to make a longer battery lifetime(I have a bigger one-6v, attached in the photo)? And for the 0v output pin from the flyback, how do I identify it? since the arc is going through most pins when I put the big red wire near it (I attached it to the yellow wire in the photo).

And a final Issue.. I have got some hv capacitors and put them in a bank...( the wiring is wrong, i think!!) . Are they able to be used in the circuit somewhere??? How about your idea??


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(author)  2 years ago

And thus, do I need to discharge the electricity inside the flyback again before touching it with bare hands?

(author) 2 years ago

This is my photos...