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Step 2: The Driver Circuit

This design is very simple and only uses four components! It is also very versatile and the input voltage can be as low as 5 volts or higher than 18 volts if the transistor is attached to a heat sink.

------THEORY OF OPERATION------

-   5 to 18 volts is fed into the circuit, a resistor (R1) is placed before the Base pin of the transistor in order to limit the amount of current the pin receives. If too much current is allowed into the Base pin the transistor can produce excessive heat and fail.

-   One end of the secondary (L2) is connected to the Base pin of the transistor in order to feed it with oscillations. The two diodes (D1 and D2) prevent the oscillations from going directly to ground. (Learn more about oscillations and why they're important, below).
 
-   The transistor is made up of three pins: the Collector, the Emitter, and the Base. If you were to think of the transistor as a garden hose spigot (See picture 2), the Collector would be the reservoir of water. The Emitter would be the hose and the Base would be the valve that would allow water from the reservoir (Collector) to the hose (Emitter). The valve (Base) is in the closed position (no water flowing) until it is given a little nudge. When it receives a nudge, the valve opens and a lot of water is allowed to flow from the reservoir through the hose as long as the valve is still getting a nudge. However, as soon as the nudge goes away the valve will close, cutting off the water from the reservoir to the hose until the valve gets another nudge.

-   When the Base receives a little bit of current, it closes the circuit and electricity is allowed to flow through the primary coil (L1). However, electricity likes to take the path of least resistance so when the electricity is allowed to flow from the collector to the emitter (~0 ohm resistance) it will stop flowing to the base because there is 47,000 ohms of resistance there. When the electricity stops flowing to the base, the base will open up the circuit again until the resistor offers less resistance than the Collector-Emitter path. This cycle repeats itself many times a second.

-   The primary coil collapses when the electricity stops flowing through it, when this happens, the secondary coil picks up the magnetic field and converts it back into voltage which gets stepped up to around a thousand volts in the process. The top load acts as a capacitor and increases the output from the secondary causing electrons in the air to become excited.

-   Finally, the oscillations from the secondary coil are fed back into the transistor in order to 'tune' or achieve maximum output from the Slayer Exciter.
<p>Can a 1&quot; wooden dowel be used instead of a PVC pipe? Can I use thicker gauge wire and a bigger top load to compensate?</p>
<p>It is a nice design. I used a 2.5 cm tube with 9 turns of 0.8 mm primary and 400 turns of 0.3 mm wire for the secondary. The coils have inductances of about 2.7 uH and 725-750 uH. Thanks for posting!</p>
<p>what is the value of the resistor that you used because i used 47k ohm resistor and i get only little spark and it was so tiny!</p>
I use a 47k as well. I do not get a spark. The idea is to light the TL tube. I have build a full Tesla Coil but that is quite a step up from something like this...
<p>unfortunately,mine stoped working i didn't know what's the probleme ,i tried fixing it by using other transistors like D304X,13003B, BUl128d but non of them worked i think the C5027s transistor works great ! :(</p>
<p>no it's working now better then befour i replace the transistor with pnp A1129 and remove the led and flip the connection of the battery and now i am getting juicy sparks that burns my finger instantly!</p>
I actually run this on 63vdc 1amps awesome arcs but I use 3watt 47kohm and a big npn transistor
<p>Nice build, and thank you for providing us with details of your build.</p><p>By chance, have you measured the power draw?</p>
<p>Hey, this is an amazing creation and i've tried to build the same.</p><p>I've used same components, the only difference is that my pipe is 1.18&quot; diameter. </p><p>I've 340 turns on my secondary and i've tried between 2 and 8 turns for my primary, but this isn't working :(</p><p>I've already tried to invert the primary after reading the comments, and i've tried with and without a breadboard ...</p><p>My transistor heat a bit but it's not very hot.</p><p>I need some help, thanks in advance !</p>
<p>I had similar problem. my transistor was getting heated up but output was not as expected. i was using a 9V battery and the problem got solved when i used 12V battery instead of 9V. </p>
<p>hey, helo, plz help me brother, i want to know how to increase the range and output power of this type of tesla coils. i've already searched the whole google. there is very less information on the google about the concept, principle and working of the tesla coils. i want to know that how this coil light up's the bulb'b without any connection to the bulbs. plz tell me the mathematical equations showing relationship between all of the parameters of the tesla coil. thnk u........</p>
<p>Thank You So Much Chip Fixes and all those who commented. I was able to make a S Layer Exciter with all the information you guys gave. Thank a Lot :)</p>
<p>I used d667ac transistor and it works.</p>
<p>Hello, I am trying to understand the calculation behind the circuit, are the primary and secondary work like a transformer or better like Ruhmkorff induction coil ? Can i so apply the following equations... (N1/V1=N2/V2) and (V1*I1=V2*I2) ? </p><p>Also how can I calculate the frequency? Thanks for your time.</p>
Help. I build one with 4 turns of 1mm copper wire nd used 2n 3055 transistor nd also used 10k ohm resistor. The secondary is 7 cm around 1/2 inch pvc. Nd is of 29awg gauge wire. My tesla coil does'nt work. I did swap the primary connection still with no success.can u help me make it work??
<p>The instructions say 5 to 15 turns on the primary. His PVC is 1 inch diameter and 6 inches long (2.5cm by 15cm), significantly larger than yours. This will put the self-resonant frequency much higher, perhaps too high for a 2N3055 to oscillate.</p>
<p>Check diode direction? Are you using ultrafast recovery diodes? Doublecheck the transistor pinout.</p>
<p>Check diode direction? Are you using ultrafast recovery diodes? Doublecheck the transistor pinout.</p>
Hi,I use TIP31C circuit<br> primary coil 4turns,<br> secondary coil 900 turns,<br> 12V UPS battery.<br>But,it can support one or two lamps with very low brightness.<br>It produce loo small spark.<br>Please,help me.How can I fix it.
<p>The instructions say 5 to 15 turns on the primary.</p>
<p>Hi! Thank you for your instructable, it's amazing =) . I have a really big problem. With the Physics Lab Assistant, I made the secondary coil and the first coil. I made the circuit with a NPN BC337 Transistor, a 10K Ohm resistor and a Red Diode (I don't remember the part number). The power passes through the resistor and the Diode, the Voltage inside the transistor and the primary coil is good (similar to the transformer input), but the secondary coil's Voltage is locked to 0,7 V and the experiment doesn't work. I don't know what I must do to make it work. The copper wire used in the secondary coil is a 1mm with no case (but, on top of it there is a sort of insulating paint, I don't know why), the primary coil have the similar wire with case. Please, help me as soon as possible. =( Thank you in advance.</p>
<p>Do you mean that your secondary wire is enameled wire? That is what you should be using. By &quot;case&quot; do you mean insulation? The enamel on the secondary wire is insulation, used instead of a plastic insulation because the enamel is so much thinner.</p><p>Without that insulating coating, the secondary is not a coil but just a pipe and it won't work.</p><p>1mm is pretty thick wire for the secondary. It means fewer turns, which means higher frequency. Perhaps it is resonant at too high a frequency for the transistor. If you cannot get thinner enameled wire, you might try winding a much longer coil.</p><p>Enameled wire is also called magnet wire.</p><p>Do you have two ultrafast recovery diodes in series, in the proper direction? A 1N4007 won't work as it is too slow. A single red LED has been used by others instead of the fast diodes. An LED switches pretty fast, and a red LED drops about 1.5V, which is about what two silicon diodes drop.</p><p>It also will only light up if the circuit is oscillating.</p>
<p>chip I have used a 24 AWG wire else I followed all other instructions properly but I am not able to get the result.</p><p>My transistor(2n2222) gets heated up and I used a 22k resistor.</p>
<p>A 2N2222 is a pretty small transistor, it can't handle much power. Also, the pinouts vary by manufacturer. Perhaps you are not connecting to the correct pins.</p>
<p>Why transistor is used in tesla coil?</p>
<p>It acts as an amplifier. There is feedback that is inverted so it is 180 degrees out of phase, if the coils are connected in the correct direction. The transistor itself amplified and inverts, so the feedback is amplified and it oscillates. The frequency is determined by the resonant frequency of the secondary, which is determined by the inductance and the parasitic capacitance between windings, from the windings to ground, and the self-capacitance of the ball on top.</p>
<p>It acts as an amplifier. There is feedback that is inverted so it is 180 degrees out of phase, if the coils are connected in the correct direction. The transistor itself amplified and inverts, so the feedback is amplified and it oscillates. The frequency is determined by the resonant frequency of the secondary, which is determined by the inductance and the parasitic capacitance between windings, from the windings to ground, and the self-capacitance of the ball on top.</p>
<p>Hello I really want to build this and I have been trying to get this circuit to work for some time, i <br>used all the same parts as you did except for the diodes I used 2 LEDS. When <br> I tried it the circuit LEDS didn't light up and got no voltage in the <br> <br> secondary i already tried switching the primary leads, I am using a 15v <br> supply and have used many different resistor values without success and <br> the transistor does heat up please help.</p>
<p>Try using one red LED. A single red LED drops about 1.5V, which is about the same as two silicon diodes in series. The diodes (or LED) is there to prevent the Base-Emitter voltage from exceeding the reverse breakdown voltage, which is quite low depending on the transistor. It must be a fast switching ultrafast reverse recovery diode. The 1N4007 is NOT suitable. An LED will switch pretty quickly.<br><br>I know this is 8 months later, but please let us know if you got it working, or if my suggestions help.</p>
Bro help me plz<br>i made this with all new parts and under your supervisions but my CFF bulb lights in the the begining and my transistor gets hot but its not a major problem but after sometime my bulb doesn't glow i found that my transistor is not working properly so i changed it with new one and again starts working but same problem happend again i changed 5 transistors but problem is happening i also used heatsink with my all transistors.<br>help me plz beacuse i don wnt to change transistor again and again
<p>What voltage are you supplying it with? You may just need to give it less voltage. It sounds like the power level is burning out your transistor. Are you using the proper UF4007 ultrafast reverse recovery diodes? A 1N4007 is NOT the same thing. I see someone else here used one LED in place of the diodes. LEDs switch pretty quickly and a single red LED will drop about 1.5V, about the same as two silicon diodes.<br><br>If you don't use the diodes, it may be slowly destroying the transistor by exceeding the reverse breakdown voltage of the Base-Emitter junction, causing the transistor to have high leakage current, heating it up.</p>
Pretty cool. I substituted the diodes with an led. Does that affect the output power in anyway.!? I wouldnt think so but this is the first one of these ive made. Also mine didnt work at first and all i had to do was swap the wires on the primary, guess i had it backwards.! I now want to make a real tesla coil and get some arcs.!
<p>LEDs can switch pretty quickly. That is probably the most important part of those diodes. They are there to protect the base of the transistor from reverse voltage breakdown. A red LED drops about 1.5V, about what two silicon diodes drop. Great! I am going to build one of these, now I want to try it with an LED as you have done.</p>
<p>I used 24 AWG for the secondary coil. How will this effect the results ? Will it not work as well ? Also does the size of the &quot;Top Load&quot; have any effect on the power ? I used a larger ball for the top, it looked better.</p>
<p>A larger ball lowers the frequency. Thicker wire with fewer turns raises the frequency.</p>
<p>hey, </p><p>i arranged the circuit as you said but couldn't get UF4007 diodes..i used 1N4007 instead..is there any difference?? is it not working because of these diodes??</p><p>please help..or else can u suggest any other series of diode</p>
<p>They are the same just made by a different plant more than likely in china </p>
<p>No, they are NOT the same. UF4007, as SohaibH says, are ultrafast reverse recovery diodes. 1N4007 are fast to turn on but very slow to turn off. At the frequencies here, they will act more like a resistor than a diode.</p>
<p>Use UF4007, they are ultra fast.</p>
<p>guys please!!!!!!! help me and please tell me about the problem but the tesla coil i tried to make is not working i used 28 awg wire as secondary coil and 23 kohm resistor ,</p><p>2n2222a transistor . 30 awg primary coil (blue wire). PLEASE help!!!</p>
<p>You probably would need quite a few more turns for the primary coil, from the picture it seems you only have 1 or 2 turns. Also, could you show a picture of it not working? Also, your transistor seems a bit too small to handle the 18V you're putting in, it may be dead, try checking if it still works. Also, try checking all of the connections (with a 3V source and a LED, if you have those on hand) to see if there are any broken connections.</p>
<p>You probably would need quite a few more turns for the primary coil, from the picture it seems you only have 1 or 2 turns. Also, could you show a picture of it not working? Also, your transistor seems a bit too small to handle the 18V you're putting in, it may be dead, try checking if it still works. Also, try checking all of the connections (with a 3V source and a LED, if you have those on hand) to see if there are any broken connections.</p>
<p>dude !! i also faced the same problem earlier...</p><p>try inverting the smaller coil and see if it work .. in my case it worked!! </p><p>cheers!!</p>
<p>It's still not working, can you please check if there is any mistake in circuit . and can you please send me some pictures of your model.....</p>
<p>oh and i forgot to mention that my circuit operates at about 2MHz!</p>
<p>I love this circuit! i replaced D1 and D2 with an inverter microwave diode. I was able to push the circuit to 30V (0.5A) for about a few minutes until the heat sink hit 60 degrees C. I didn't want to bring the tip31c higher than 30V because that's about 1/3 its rating. thanks for the upload!</p>
<p>I built a slayer exciter but I'm having trouble with it. I may have made it too small. I used a 1/2&quot; inch PVC pipe which then has an outside diameter of .625&quot;. I used 350 turns of 30 ga magnet wire and then just used 2 turns for the primary (tried more and less and this was the only way I made it oscillate). Now the rest of the circuit was the standard with a 2n2222 transistor (ended up using two in parallel to keep the heat down) and a 22,000 ohm resistor. Now it does oscillate, because I can bring the probe of my oscilloscope near it and see the waves on the screen at 4.5 MHz. I also found that it had to be oscillating because the led lit up and also I can remove the base resistor completely while it's running and it doesn't change anything. My problem is that it won't light anything - no flourescents, LED's, little neon bulb or anything and the oscilloscope indicates it is only cycling at maybe 15V p/p on the top. I'm getting about 87ma (RMS) to the primary. I even put two in parallel to cut the load to each. I've tried different transistors with higher current but they wouldn't oscillate. I've tried different numbers of turns on the primary both tight wrapped and loose and slid up the secondary and down in different positions. Can anyone help tell me what I may be doing wrong. Everyone on the internet that builds one makes it seem so simple.</p>
<p>OK I got it working for those who are interested. The basic problem was that I had it breadboarded as you mentioned below. I didn't think that would matter since it seemed to oscillate even on the breadboard, but when I soldered it up just to try, suddenly it worked! So thanks to those below who suggested that. I also had a problem using my one homemade power supply apparently because it had a ripple interfering with the pulses from the secondary. Anyway, small as it is, it works, even if it doesn't have much power (uses just 57 ma now that it's soldered). Thanks again for all the little helps throughout the site.</p>
<p>Hello,</p><p>I have followed the instructions as best as possible, but I am having a problem.</p><p>My voltage at the top of the secondary is the same as the input voltage. Any ideas? </p><p>Thanks!</p>
<p>The problem is that you are using a breadboard. Breadboards have a capacitance between each row and this is a high frequency circuit (up to the order of gigahertz) and this capacitance messes with how the circuit operates. I hope this helps.</p>

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Bio: Working with electricity has been my hobby since I was 8 or 9. I have always loved to take stuff apart and redesign it in ... More »
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