High voltage experiments: Part 3 - Homemade flyback transformer using ferrite rods

I am still lingering around flyback transformer and never start my tesla coil design since i am too absorbed and keen to know how does the flyback transformer work. For your information, before i got to have the ferrite c cores from the original flyback transformer from CRT tv, i have purchased four ferrite rods from Ebay as i ve planned to made them into my own handmade ferrite core or frame. As the rods were still in my room and i ve got nothing to do with it therefore i decided to resume to this plan, with a hope i will get useful knowledge on how the flyback transformer really works, and also a 'painful' experience in hand-winding the secondary coil of the transformer by myself!

By using the circuit in the previous post i ve tested my second handwound homemade flyback transformer, and surprisingly, it worked and as always, the beautiful blue/purple sparks appeared! I thought it would not working cuz i was just using ferrite rods which may be different from specially engineers-designed ferrite c cores for the original flyback transformer.

Before I move on, here is my current variant of the schematic. Please bear in mind that this circuit is designed by an amateur, so be careful with the high voltage output. This is not my final design and i am still improving it. I ve made my own Mazilli driver but it baked my MOSFETs ( due to minor mistake for not putting zener diodes)! So I retreat to this 555 driver but with separated power supplies cuz the circuit i ve been using before had damaged my 555 chip. Here is the schematic:

click for larger version

Please bear in mind that the value of the capacitances and resistances are not critical. You may change and experiment with other values depending on their suitability on your designed transformer. I m not an expert on this, so be careful cuz u are dealing with high voltage!

Without photos, there is no meaning. Therefore, i prefer speaking with photos accompanying me:

The overall setup. The flyback transformer i ve made with the ferrite rods frame is shown having yellow-taped secondary winding (larger winding) with red-taped primary winding (smaller winding), each wound around a ferrite rod, separated with two other ferrite rods on top ( visible) and at bottom ( invisible, located in the handmade box in white, near to the circular support from cellophan tape, under the transformer). Look at the following photo if u dont understand what ive meant:

Closer view on the circuit.

The flyback transformer. Note the spark gap on the pc cooling fan box.

Sparks were succesfully produced between the gap, but less powerful than those generated from original and homemade using C ferrite cores. I reckon that might be due to larger air gap within the core, and also might be due to saturated ferrite core.

Here are the photos explaining how the overall structure of the flyback transformer was made:

The complete assembly of my ferrite rods flyback transformer.

The top ferrite rod ( external diameter 1 cm, length 6cm, bought from Ebay) was removed from the structure to reveal the assembly. I used four similar rods to create the ferrite frame akin to that made of original double C ferrite cores in the original flyback transformer. Notice there are two other rods arranged vertically, wound with primary and secondary coils respectively. The last rod was embedded at the bottom of the structure, in the square base that will be explained later on.

The primary winding, wound on a similar ferrite rod, was taken apart. I just wound a common single core breadboard wire with about 12 turns, and then concealing the winding with the red PVC tape.

The secondary winding. I used similar method as before, except that i double the number of layer so it became larger and fitted the larger frame due to the dimensions of the rods. I also have changed the enamelled copper wire to smaller one ie 0.4mm external diameter. I dont know the exact number of layers and turns i ve made since its quite daunting to calculate it while u hand winding them. I just made it large enough so its distance from the primary coil is less than 1 cm. For this secondary i ve spent two days, each day i devoted about six hours of my life winding it, giving a total of 12 hours winding time. Thats approximately how much u will get if u produce it without special machines or toolings. I recommend u to make it to learn, since this thing cannot be learned by mere reading. U have to experience it in order to learn it.

The secondary is completely taken apart, revealing the white box that constitutes the base of the device and housing of the bottom horizontally configured ferrite rod.

Secondary winding, closer view on its leads. The yellow wire is carrying high voltage, while the smaller enamelled copper wire (0.4mm diameter) extended from the winding, is the high voltage earth.

Here are the photos of the square base:

The box is made from pizza's box. I cut it into shape desired to form the box that can house the ferrite rod and support two windings ferrite core vertically. The ferrite rod can be seen lying in the horizontal pit within the box. To make it u just simply need a cardboard (pizza box for convenience), tape, and scissors.

One main message that i want to convey thru this entry is that, if u have ferrite rods instead of ferrite C core, u can still make your own flyback transformer without need to spend money on buying such cores which are now becoming rare since most TVs now are using LCD screens. Therefore dont easily give up, just make it. And i have proven it to you that it works!