Saturday, 23 July 2011

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:

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!

Tuesday, 19 July 2011

High voltage experiments: Part 2- Homemade flyback transformer.

As i ve said before, in this second part i will show you my high voltage experiment using my own hand-wound homemade flyback transformer using the ferrite core from the original flyback transformer salvaged from old cathode ray tube (CRT) television monitor.

Before I move on, here are the photos taken and descriptions:
The overall setup. I ve changed the power supply from stacks of battery into regulated laptop power supply (indicated by black wire on the left) that can safely adapt power from the mains for project purpose. It supplies 9VDC at 3.16 A. I ve been using same inverter circuit i ve always been using before, except that for R3 i use 500 ohm, R1 at 3kOhm, and 10k potentiometer for R2 for easily varying the operating frequency ( pin 7 of 555 is connected to swiper, pin 8 to one of the end pin while the other end pin is left unconnected, so this potentiometer is modified into varistor rather than potential divider). Also to protect the mosfet i ve put a snubber diode 1N4148 in series with 464kOhm resistor, across the primary winding of the transformer, between the supply line and the mosfet's drain pin.

Closer look on the circuit. I use copper heatsink ( the finned chunk of brownish thing) for protecting mosfet from overheating.

Closer look on the left side.

Closer look on my homemade handmade flyback transformer

This is the original flyback transformer from old CRT tv monitor.

...and this is how the double C ferrite cores are dismantled from the transformer.

The primary winding. I made it to be fitted enough into core. First I take an old pamphlet paper ( since its not too hard) then i rolled it around the core, and I retained the cylindrical shape of the rolled paper using common tape. Then over the cylinder, i rolled one layer of PVC tape, and the purple wire. I added another layer of common tape so the purple wire coils firmly positioned on the red PVC tape. Notice i ve used 15 turns, but its up to you to use any number of turns as its only affects the amount of current u 'll get on the secondary.

Bird eyes view of the primary

The secondary coil. Same method with the primary ( also made to be well fitted on the cylindrical structure of the ferrite core), except that i used 25SWG ( about 0.5mm diameter enamelled copper wire) for the winding, with about between 30 to 40 turns per layer, and i ve had about 10-12 layers for that ( I dont quite remember), so there are about 350 to 400 turns overall. I am still using PVC tape and common tape for each layer. More on this design of secondary can be found here.

Bird eyes view of the secondary.

The components ready for assembly.

And it really works...

See ya next time.

p/s: after several times using the power supply, the 555 chip was damaged and i have to replace with new one. This maybe due to high current surge since i m using 3.16 A. Therefore I recommend you to put resistor (for example 500 ohm) between the supply line and any direct input from the supply into the 555 ( pin 4 and 8). To date, i connect pin 4 and 8 together, and link the node to the supply with a 500 ohm resistor. Though the spark becomes shorter, this method may prolong the 555 lifespan and u may still have fun with the spark.

Sunday, 17 July 2011

High voltage experiments: Part 1- Flyback transformer

I admit that i am a very detailed learner and experimenter, who appreciate the fundamentals more than going straight to the target or subject i want to study. Thats why, you will see several experiments before i move on to making my own version of Tesla coil.

One of them that i ve been planning is two high voltage experiments using flyback transformer; one is salvaged from old television ( part 1, which is this entry) and one made by myself ( the ensuing part 2)

Flyback transformer is a special resonant transformer invented to generate high voltage, high frequency current. This transformer is mostly used to control the horizontal deflection system in any visual devices such as television and pc that are using CRT or cathode ray tube. That is why if you want it, as an alternative to buying from retailer or internet, u can also salvage it from old aforementioned stuffs.

Nowadays, its getting harder and harder to find old television and pc that has this kind of transformer since most of nowadays tv and pc are using LCD screen, so flyback transformer has no market at all ( msot companies stop producing CRT-based tv and pc from 2010 onwards, see wikipedia). Therefore, if u manage to get one, value it! I was so lucky yesterday when i was wandering around the rag market in the town searching for a used television, an old man was having it and sold it to me for about 10 pound. Besides flyback transformers, I also got other useful components for my other projects from the old tv such as speaker, electronic components and the second-most wanted stuff: the cathode ray tube ( so I can play with high freq voltage on it!)

By using the previously outlined circuit that used battery charger transformer to get sparks , i just substituted the transformer with the flyback transformer I got from the old tv. The pinout of the transformer is as follows:


I got longer blue/purple sparks between the electrodes of the transformer's secondary, which is between 1cm to 3cm. Since my multimeter could not load high voltage thus i just reckoned that the voltage is about between 10 to 20 kV. Here are the photos taken:

Overall setup. The battery pack is actually 12V, there are other five cells under the three. The black bulky object with medium length fat wire is the so called flyback transformer. The fat wire is the outlet of high volt high freq current. Notice there is a 10k potentiometer. I substitute it for R2 in the 555 timer inverter diagram before. There is also heatsink where the MOSFET is attached to ( MOSFET cant be seen in the photo). The purple wire stretching out from beneath the transformer is the ground of the hi volt outlet. Please ignore the yellow wire in the picture,including the one wound on the transformer.

Purple wire is lengthen ( using additioal wire, thin yellow wire in the photo, now ignore the thick yellow wire wound on the transformer) to a spark gap, where the fat wire is also attached to its other end. The black rod is just fix the fat wire and the spark gap wire together and serves no other purposes. Two thin yellow wires from beneath the transformer are linking it to the main circuit on the breadboard.
Two medium size wires from the upper part of the transformer are not used.

Ready for experiment.

Closer look on the spark gap, where the spark will be observed.

and here are them:

Next post will be using my homemade flyback and better kind of power supply for more powerful spark.

Saturday, 9 July 2011

My baby Tesla coil.

I started building Tesla coil by first learning how to build an inverter from DC supply. I found an inverter circuit here made by Joshua D. Wyatt, from this link.

There, he used the inverter circuit to power EL backlights and fluorescent tubes, so the output is about 127 VAC as he claimed. But I want 1kV or more to make at least 1mm purple plasma as Tesla coil usually produce! (30kV is required to make 1cm length plasma). Therefore i use MOSFET IRF 840 as a transistor for high switching rate (also any IRF-named MOSFET will do, such as IRF741 and 630) and also transformer i use before from cracking open a battery charger to step up the voltage to more than 1kV.

Here goes the schematic with specifications following it:
I used:

R1: 100kOhm. Again up to you. Its values controls the duty cycle of the triangular pulses generated at the end of the MOSFET.
R2: 464kOhm or more, up to you ( you experiment it yourself). This resistor controls the frequency so different values produce different sound pitches of the plasma ( it produces buzzing sound depending on its operating frequency)
C1:0.047 microFarad
C2:0.01 microFarad
C3:0.1 microFarad
C4:100 microFarad
Q1: MOSFET transistor N-channel IRF840
T1: step down transformer from battery charger (converting 240AC to 2.8DC). For this project I inverted its function as a step up transformer.

The plasma length is about 2mm maximum, with the output voltage of about 1888V (I think it should be slightly higher since my multimeter couldnt measure it due to its almost broken and internal red light was seen flashing inside! I dont know where the light came from,there is no warning LED there, but my multimeter still survived that thrilling incident).

Here are the photos taken:

Just showing the transformer and red leads ( the plasma producing leads). I hate the circuit since it looks messy on the breadboard ( i hate soldering my projects...haha

The spark is very small, like i said before its 2mm in length. So small, and purple in colour. Cuz this is my 'baby' project before moving into the main one ( i m waiting for my copper wire to arrive to create my own flyback transformer)

Another photo from same angle, booooriiinnggg....

OK, gotta sleep now...bye

Friday, 8 July 2011

LM386 is godsend.

LM386 is very fun. It is a multi-purpose power amplifier 8 pin chip designed to amplify small power. I ve used it to amplify small signal from my crystal radio receiver and it works marvelously! It can even power up an 8 ohm speaker, to the sound level of mobile phone speaker.

This amazing chip i bought from Ebay for GBP 3.17 , and got ten of them. To use it as crystal radio amplifier, just Google the circuit schematic. I ve used the following schematic from


Is LM386 only amplifying audio signal?? Nope. Like i said in first line, it is a MULTI PURPOSE POWER AMPLIFIER. Therefore, I deduced if I can amplify sawtooth signals generated from ubiquitous 555 DC pulse generator chip (another chip, not to be confused with LM 386), and further amplifying the resulting pulses with transformer, then I can get high frequency, high voltage, low current alternating current. Lets see...

The overall view. At the very left is the 12V DC battery power supply. Note two chips on the breadboard. The first one is 555 timer while the second one on the right side is the so called LM386. At the very right lies the so called transformer. I cracked open a battery charger to get this transformer, which its original role is to convert 240V AC current from mains to about 2.8V DC for battery charging purpose. I inverted its role as a step up transformer, by connecting its secondary to the circuit on the board. By applying 12V to the circuit ( where 4.3V goes to the primary of the transformer that linked to the circuit), I got 183V, 66mA alternating current at the very end of the transformer's secondary ( the red wire at the end of the transformer, see the magnified view below).

The close look on the transformer. The red ends are carrying high voltage between them (183 VAC), high frequency (about 200Hz) low current (66mA). When you touch it, you will feel a zap, but more pleasant and less painful than conventional shocking pen. I touched it many times becuz it felt great. :P

What amazed me the most about the high voltage high frequency current circuit above is that when I touch the two red ends, I felt the same impulse i ve got when I touched the shocking pen few years before but less painful and more fun. Back then, I wondered how did the shocking pen (shown by my friend to me) can gave such a very painful shock, now i manage to build the circuit myself! Haha. But poorly, this big circuit never ever fit any pen. Maybe its miniaturization will become my next project.

The ensuing photos explains more than words can do...

The circuit...actually the LM386 parts ( the power amplifier circuit) is just the one being depicted before. The 555 part can be Googled anywhere, it generates spike signals. I used spike signals rather than square or sinusoid since spike gives more intense impulse to our fingers. :D

The overall circuit. I dont know how to rotate it, you do it yourself.:P

Next project, small Tesla coil. Gotta work, see me in the next post.