Intro:
This instructable will show you how to make a cheap and simple driver circuit in order to get high voltage arcs out of a component called a flyback transformer.
A flyback transformer, sometimes called a line output transformer are used in older CRT TV's and computer monitors to produce the high voltage needed to power the CRT and electron gun. They also have other auxiliary windings built into them that the TV manufacturers use to power other parts of the TV, so they are usually customised by the manufacturers.
For the high voltage experimenter they are used to make high voltage arcs, which is what this instructable will show you how to do with just a few simple electronic components.
You can get flyback transformers out of older CRT monitors and TV's. They are the ones that have a big heavy chassis. There are also other instructables on this website showing how to remove them from the chassis and circuit board.
Disclaimer
I am in no way responsible if you mess up with this circuit. If you mess up you have no one to blame but yourself.
What you will need:
1x Flyback transformer
1x 2n3055 transistor + heatsink
1x 220 ohm 5 watt resistor
1x 22 ohm 5 watt resistor
(Note: The resistor values do not have to be exact. Say if you had a 33 ohm and a 200 ohm resistor they would still work fine for this circuit).
Some enamelled magnet wire, single core bell wire also works well too for the primary and feedback coils.
A fast diode. Although this is not needed for the circuit to work, it protects the transistor from back emf spikes and can help prolong the life of the circuit. I just used the one I found on the TV board but the UF4007 is an easy one to get hold of in electronic stores if you need to buy one.
+Some way of connecting the components
such as alligator clipped cables or wire and solder.
You may not, except with our express written permission, distribute or commercially exploit the content. Nor may you transmit it or store it in any other website or other form of electronic retrieval system.
This instructable will show you how to make a cheap and simple driver circuit in order to get high voltage arcs out of a component called a flyback transformer.
A flyback transformer, sometimes called a line output transformer are used in older CRT TV's and computer monitors to produce the high voltage needed to power the CRT and electron gun. They also have other auxiliary windings built into them that the TV manufacturers use to power other parts of the TV, so they are usually customised by the manufacturers.
For the high voltage experimenter they are used to make high voltage arcs, which is what this instructable will show you how to do with just a few simple electronic components.
You can get flyback transformers out of older CRT monitors and TV's. They are the ones that have a big heavy chassis. There are also other instructables on this website showing how to remove them from the chassis and circuit board.
Disclaimer
I am in no way responsible if you mess up with this circuit. If you mess up you have no one to blame but yourself.
What you will need:
1x Flyback transformer
1x 2n3055 transistor + heatsink
1x 220 ohm 5 watt resistor
1x 22 ohm 5 watt resistor
(Note: The resistor values do not have to be exact. Say if you had a 33 ohm and a 200 ohm resistor they would still work fine for this circuit).
Some enamelled magnet wire, single core bell wire also works well too for the primary and feedback coils.
A fast diode. Although this is not needed for the circuit to work, it protects the transistor from back emf spikes and can help prolong the life of the circuit. I just used the one I found on the TV board but the UF4007 is an easy one to get hold of in electronic stores if you need to buy one.
+Some way of connecting the components
such as alligator clipped cables or wire and solder.
You may not, except with our express written permission, distribute or commercially exploit the content. Nor may you transmit it or store it in any other website or other form of electronic retrieval system.
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Signing UpStep 1: Mount the transistor onto the heat sink
Mount the transistor onto the heat sink. The heatsink is important as the transistor gets hot. I just bought the cheapest heatsink maplin sell. The 2n3055 is a TO-3 case style.
You can use an insulator pad if you want but I just used a small amount of old thermal grease I had lying around. To mount the transistor to the heatsink I just used some spare screws and nuts I had in the garage.
Make sure that the transistor pins do not physically touch the heatsink and it is screwed in securely.
Q: Can I use a different transistor?
A: Yes you can, as long as the transistor has similar specs to the 2n3055 or better.
Q: Can I use a PNP transistor?
A: Yes, but you will have to reverse the collector and emitter connections in order for it to work. It will also need to have similar or higher specs as the 2n3055 transistor.
Q: Is the heatsink really needed?
A: Yes, if you are wanting to use this circuit for more than a few seconds the heatsink is vital as the transistor will get hot fast.
Q: Can I use a MOSFET?
A: No, a MOSFET will not work for this circuit.
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Try checking for continuity between the coils and rest of the circuit as with magnet wire it is sometimes hard to get a good connection.
If you put a quarter watt resistor in there though it would be a different story (small resistor + lots of heat = flames lol).
Tried 3 different flyback transformers, 2 transistors, two different windings (7 x 11 and 5 x 20), powered from both 2 x 6V dry cells in series and also a car battery, triple checked continuity and resistance on all parts, but.... no spark! Not only no spark, no heating of the transistor, no noise, nothing. Is this a hoax?
How does this circuit create a high frequency oscillation? Why does mine create neither sparks, no noise, no noticeable heating of any component? Components: radio shack 2n3055 transistors, 220 and 22 ohm 5 watt ceramic resistors, tried with and without the diode. Any ideas?
No this is not a hoax, with it working when you first apply power to the circuit current flows through the potential dividers and into the base (which the potential dividers bias it to at around 0.8v). As the transistor begins to turn on current starts flowing through the primary coil (storing energy in the core) into the transistors collector, out of the emitter and then to ground.
But since there is the feedback winding sharing the same core current will be induced onto that too. This is why it needs to be connected in the correct polarity so that the current induced onto this winding turns the transistor off. When it does turn the transistor off the voltage across the primary coil will be now ring up to many times that of the original input voltage, and so will the secondary coil thus causing the HV.
This is also where the fast recovery diode and maybe a small capacitor help to protect the transistor.
Have you checked each individual component out of circuit? A good transistor should show about 0.7v drop between the Collector-Base and Base-Emitter junctions. If you used magnet wire for the coils then check for continuity there as sometimes not scraping enough enamel away makes for a bad connection. Also when winding the coils it can be easy to accidentally scrape of some of the enamel with the core edges and that can create shorts between windings.
Check the current draw too of the circuit and the voltage of your power sources when under load.
Hopefully you'll get it working ( :
Also have you tried reversing the primary and feedback connections?
You could get some small sparks though by manually pulsing the battery through the primary coil (although they would be very small and hard to see).
This circuit self oscillates and gives the primary coil the high frequency pulsing DC it needs to function (plus the flyback "back emf", that is the real reason for the high voltage).
1.I used the same power source as your, 12V, 8 of AA battery
2.I don't know clearly what you mean in this point,I made the same polarity both of the primary and feedback and primary turns are more than feedback.
3.I used to make 20 and 12 turns of primary and feedback respectively and I used the enameled wire about 0.5 mm as the coil.
4.Yes,the voltage dropped quickly after few minutes when i switch on. But in the first, batteries just load,there is a shorter arcs than your.(suppose there is 12V when new batteries just load).
Thanks again for giving a direction
If I used a 110VAC house main, and sent it through a bridge rectifier to change it into DC, could I use that instead of the 12VDC battery? Or would it blow the circuitry?
Or, could I send the 12VDC battery through an inverter, increase the voltage through a step-up transformer, rectify it back to DC, and then but it through the flyback circuit?
Might be a good idea to put a ceramic or film capacitor across the supply rails for decoupling (close to the driver) to help stop any protective features from kicking in if the LOPT/flyback transformer spits out lots of noise on the supply rails.
Many thanks,
- sleepyjz
Did you put the diode the correct way around?
Have you got any spare computer or desk fans lying around? Using a fan on the heatsink will help.
One way of cutting down the back emf pulses is to use something called an "RCD snubber" across the primary coil, however they can be tricky to get right. And putting anything across the primary coil is going to cause a smaller arc since the back emf (this is where the word flyback comes from) is the only reason there is such a high voltage coming out of the flyback transformer.
Perhaps try putting a small film capacitor across the primary coil, anywhere around 0.47uF-1uF. You will get shorter but much hotter and thicker arcs and it should help reduce the MOSFET heating. You might have to play with the values and flyback frequency (adjust the pots) to get the best results.
As for MOSFET temperature, what MOSFET are you using? They can easily survive upto 150C, although that is with a large fan cooled heatsink.
One last thing, which circuit diagram version are you using? The first one I uploaded doesn't allow for fast MOSFET switching becuase of the resistor between the 555 timer and power supply.
Hope this helps.