Anatomy of a flyback transformer

[LiveRock]

Hi

I am totally new to HV. I just brought a 50KV flyback transformer because I need to build a 25KV DC power supply for my N2 Laser. I've searched the internet and there are quite a number of driver circuits but I am lost as which one suits me better and the most important thing, I am not sure what the wires of flyback transformers are for...

My flyback has a label 'Orion A 12.1' and is the cylindrical type.

It has one very think red wire than comes out from the top... what's this?

At the primary core, there is winding with 2 wire, one yellow and one red.

At the secondary, there are 2 wires, one orange and a thicker white.

There are 2 knobs with labels 'Screen' and 'Focus' at the back that can be turned.

At the bottom, there are 3 pins, with one marked as '+'

I am quite confused as what these are and I am really hesitatent to connect this to a driver circuit.... an explosion is not I want :=)

Please, someone shed some light into this wonderful and yet strange device!

Thanks!

 

[LiveRock]

Here are some pictures:

 

[tdwister]

Hello,

I too got a couple of these flybacks.they are not great as far as I can tell. I have tried to get a pin out from them with no luck, (you got these on ebay, right from K&plans) I found the return for the secondary (the big red wires other side or ground for the HV) unfortunately it is one of the cut pins. The 2 pins that are next to each other are the primary winding

View attachment 39906

 

[LiveRock]

Hi tdwister

Thank you very much!!!!

Yes, I bought it from K&plans, eBay. It states that it is able to do 50KV!!
Anyway, K&plans forgot to ship the small board that I also wanted and now I am still waiting for it to arrive.

I must say, your explanation shed more light into this crytic device than what I can gather searching the internet. Many sites assumes you already know where and what the wires are..

Thank you very much!!

I hope I can build something to fire my N2 Laser soon!!

I agree that this is an awesome site!!

 

[LiveRock]

Hi tdwister

I am still a bit confused here after studying my flyback....

My summary:
(a) The BIG RED wire is the HV positive
(b) The WHITE AND ORANGE wires near the BIG RED wire is not used.
© Beneath the flyback, the 2 pins with one marked (+) is the primary side
(d) The coil at the ferrite is not used.

Am I right?

Thanks and regards,
Peter

 

[tdwister]

You have it, I did not use the orange and white wires, but they may be taps off the secondary winding. also the HV ground or return, it is one of the cut pins I marked.

I got much better results winding my own primary winding, I wound 4 or 5 turns of 16 gauge  magnet wire around the ferrite, and used that as my primary, I got about 35kv out of the secondary. with a pulsed 12 volts on the hand wound primary.

I am sure you can get close to 50kv out of it but it will require more than 12 volts  on the primary that is inside the flyback. the board that they are selling, to me looks like it has a spot for a 12 volt reg. the max rating for the 555 vcc  is 15 volts, so I do not see how they are getting 50kv with that flyback and board. In my opnion, anyway.

 

[LiveRock]

Hi tdwister

I just received the small PCB; as what you have said, there are no documentation on it at all....
Thank God for your drawing...
I just need to get at least 25KV out from it. Do you have values for

(a) R1 and R2
(b) Pot 1
© C3
(d) MOSFET. I am thinking of IRF840 (specs http://www.futurlec.com/Transistors/IRF840.shtml)

Since you have already 'done it', I think I just follow whatever you used...

Also, do you think I can do a 'Jacob's Ladder' experiment from the output?

Thanks and hope to hear from you soon.

Cheers!

 

[tdwister]

I think a IRF460 is what worked best for me, it is overkill. with this board using a 7812, you wioo only have 12 volts to play, with that I had to wind my own primary.

You can use a bunch of diffrent values, from what I have read 15k to 20khz works best, but I have not played too much with the frequency. these values will work,

in r1 use near 47k, in r2 use around 22k, and for the pot use 5k or 10k for a cap use .001uf . or use the formula in the drawing  here is an example say the pot is set to 0 ohms  47000 + (2x22000) x 0.000000001C = 0.000091 then take 1.44/0.000091= 15824Hz

I do not know about Jacobs ladders
Be very carefull with this stuff

 

[LiveRock]

Hi tdwister

Thanks!

I shall use the following values R1=33K, R2=22K, 5K POT and 0.001 uf and IRF460.

I will also use 12V too, I just need 25KV.

BTW, how do you measure 15KV!!

Thank you very much.

 

[tdwister]

To measure HV you can buy a HV probe, or I make a voltage divider, then read the v drop across, the or a resistor, use the formula       

    E                          '
-------------
I  x  R

It seems to me, you should probally do a lot of reading, I do not know how much info is on this site, but if it is not here you can find it with google.  this is very dangerous stuff. If you have a nitrogen laser, it probally has some big caps in it, they will hold a charge for quite a while, if you grab a lead, evem when it is disconnected from power you can get it good. (sometimes much more power in a cap than the source that charged it) be carefull. Read Read Read.

 

[LiveRock]

HI tdwister

Thanks for the advise. I have come across zillions of warnings about high voltage stuff and I know it is lethal and mistakes can be fatal. Thanks again for the reminder...

I am threading carefully because there are still a lot of unknowns..

For example,

(a) The HV output from the flyback should be pulsed DC, right? (If if has a built-in diode) I am not sure the one I got from Plans & Kits has one...

(b) The back-emf at the primiary, will it fry the MOSFET IRF460? Some circuit I saw include a capacitor and a diode across the mosfet...

© Can the HV of the flyback be open circuit? Like not connecting to anything; will it get fried.. I am thinking of connecting a 'jacob's ladder' assembly directly to the outputs of the flyback...

(d) Do you know what is the current draw for the 12V? I have a 12V, 2 amp supply but I dun know if this is sufficient.

(e) There is a beefy capacitor in my N2 laser unit. The seller from ebay told me it needs 25KV to self fire. That is why I am building this HV stuff..

(f) I thought of an alternative lately.... I have an electronic hand-held mosqitoe zapper. It is rated at 2000V at the output and runs on 2 nicad batteries. I think if I build a 10 stage voltage multiple (cap & diodes) and connect it to the output, I can get near 20KV. Does my idea make sense or is it just nonsense....

Thanks and hope to hear your insights on the subject again....

Cheers!

 

[LiveRock]

Hi

I have wired the PCB, Flyback all together, soldered all the components but it doesn't work:=(

I am able to see an AC at the primary o/p of the PCB around 7-8 V a.c. (actually pulsed DC) but I can't seem to get anything from the flyback HV output. The MOSFET IRFP460 doesn't even get warm..

What am I doing wrong here??

 

[LiveRock]

It works!!

Hooking the flyback directly to a make-shift jacob's ladder using some copper wire used for decorations, I am able to get purple coloured arcs with hissing sounds...

It is drawing about 1 amp when the voltage is 15 VDC.

The reason it didn't t work was that my previous supply was not able to supply the required power.

Here is another pic:

tdwister is right on the flyback pinouts, capacitors and resisters values... kudos and thanks to tdwister!!

 

[LiveRock]

If I feed the outputs of the flyback transformer to a voltage multiplier made out of capacitors and diodes, will it work?

I still need to get 30-35 KV to fire my nitrogen laser. I have no idea what voltage is generated by the flyback but I think it is still not enough to fire my nitrogen laser.

I read that voltage multplier works only with AC but the output from the flyback is probably pulsed DC so I am not sure.....


anyone out there done this before?

 

[LiveRock]

Hi

New Projects I have done lately:

Building a rack-mount, 3 LCDs Panel to monitor my computers:
http://www.hotsource.net/projects/main.php?cmd=album&var1=LCD/&var2=1

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