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.


-   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.
works great
<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>Why transistor is used in tesla coil?</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>Works great. Not good at lighting up two bulbs. Will probably add heat sync so I can turn up the volts.</p><p>Nice project :D</p>
<p>I followed all the instructions and have made it :)</p>
tell me how to connect (i)coil of PVC pipe to the head coil (ii) the head coil?????
The head is not made of coil, its aluminium foil. just wrap the coil on pvc pipe precisely (connect one end of coil to the point given for it in circuit and the other one to the top load).
sir....hlp how to made power suplyr..
In this Tesla coil we are giving 9v DC supply and how we are getting output Ac at secondary ..please tell me
in the circuit digram we use such components like used in ups to convert DC into ac
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.!
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>I'm not very familiar with slayer exciters but want to build one which air core diameter is 4 cm, using 0.25 mm (30 AWG) thick enameled wire as in this instructable, but using 850 T on secondary. Will it have a better range if I use more windings on the secondary? And I don't know how many turns on the primary should there be if I put 850 turns on the secondary, is there any equation for this ratio? Thanks! </p>
<p>I did everything as told &amp; my transistor, diode &amp;resistor are heating up but my coil wont work. My science fair is in 2 days so i need HELP!! fast.</p>
If everything is warm to the touch but not hot then that's a good indication that the driver circuit is working properly. Try flipping the ends of the primary coil around and if that doesn't work, try changing the top load.
<p>I did everything as told &amp; my transistor, diode &amp;resistor are heating up but my coil wont work. My science fair is in 2 days so i need HELP!! fast.</p>
<p>Everyone please, mine is not working :(</p><p>I'm new on electronics and also in instructable.</p><p>So i followed exactly like in the diagram (except the switch), so at first i am confident mine will works too..</p><p>need for my project, am i doing something wrong?</p><p>1) Whenever i have just done connecting the wire to the battery, i touch the driver circuit, and the transistor was hot! I don't know why but i haven't switch it on.</p><p>2) I am getting panic. So i release all of the wire i've just connected.</p><p>3) I just want to know why its not working, so i added them again and checked it with my lamp (it's not working)</p><p>4) Try with LED , still not working</p><p>5) Touch the transistor, is not getting hot anymore.</p><p>Really appreciate any recommendation, don't know how to fix this..</p><p>Then, is my driver circuit right? Really i have no one here to ask for.</p>
<p>Transistor might dead.Try to swap the primary's connection and also Double check your connections.Hope this help. Good luck and Happy building. :D<br></p>
<p>When i connect top load my coil wont work, it works without it.</p>
This thing does'nt works <br>I dont understand how to arrange tge circuit on breadboard.<br>Please help, this is my first time on instructables and electronics too.
<p>Hi, i am willing to try to help, do you have a specific problem that you know of, or is it not just working?</p><p>Also, a solderless breadboard isn't the best way to due this as many are rated for relativly low amperage.</p>
Mr. Fixes<br>Are there any altranatives for the length and thickness of the wire for the coil.
Mr. Fixes<br>Are there any altranatives for the length and thickness of the wire for the coil.
Are their any replacements for the thickness and length of the wire<br>
Hiii iam Febin....sir please help me...I'm confused with specification of primary coil
<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>Use UF4007, they are ultra fast.</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>
My cfl glows sometimes and sometimes not.. Whats the problem? Using all fresh parts!
<p>If your theory was correct, than the circuit would still oscillate if the primary was replaced with a light bulb. infact, the bottom of the secondary provides <em>negative</em> feedback, and this is what switches off the transistor.</p>
<p>I've been trying to build one these and I'm finally towards the end of it and I'm have a dilemma on types of wires, I have 30 awg but with out any enamel, and 26 with enamel which should I use? The primary is either going to be 22 or 20 awg if that helps.</p>
you need the uncoated wire, and the fact that it is 30 awg is a plus, because the more turn s on your secondary, the more efficient it is.
<p>What is the range of this ?How far can I light up a light bulb ?</p>
I made this circuit, and it works very well!! :)<br>
<p>Hello! I am a high school student and I am researching topics to do for my science project. Slayer Exciters (and tesla coils) intrigue me and I would like to know if you could explain how they work exactly before I consider it as a choice. You stated that: &quot;A Slayer Exciter is an air-cored transformer that steps up a very low DC voltage to a very high AC voltage.&quot; Would you mind explaining what that means (like what is DC voltage and AC voltage)? </p>
<p>I don't mean to sound condescending; I want to help. If you don't know what AC and DC is, then explaining pretty much any part of this instructable isn't worthwhile because you wouldn't understand. </p><p>My advice is to use google. You can read, learn about, and teach yourself anything and everything you want through google searches.</p><p>So, first google Alternating Current and Direct Current (the AC and DC.) Read up on all the articles related to and linked in the AC and DC articles; everything related to electronics. Transformers, resistance and resistors, capacitors and capacitance, transistors, diodes, etc. Maybe get yourself an electronic starter kit online and follow the directions and play around. Once you have a base knowledge you can come to instructables like this one, instantly understand what you're dealing with, and have a good time doing it yourself.</p><p>I used to have no knowledge of electronics either, and believe me, projects like this you cannot do without an understanding of electronics. This isn't something that you can just follow the instructions and finish with a working product. In addition to knowing what the steps are, you need to know why you're doing each step. </p><p>Google and read as much as you possibly can and have fun!</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>
Hello everyone, i want to make this as my science project. But i am confused. I can't seem to understand the need for two diodes in the circuit. What is the function of two diodes?
<p>***Please reply. This is an EMERGENCY***</p><p>Hello! I have been trying this circuit for a while now but I haven't succeeded in making it. I have used all the components you have mentioned and also tried replacing them with other equivalents but it just doesn't seem to work.</p><p>I get no voltage across the primary even when taking the input voltage up to 18 volts. And even when I do get a little voltage at times there seems to be no induction between the coils. I have used a 22 AWG coppoer wire for the primary (4-5 turns) and a 30 AWG wire for the secondary. The secondary is roughly 7-8 hundred turns (diameter of the secondary being roughly 1 inch and the length being roughly 7-8 inches).</p><p>I have been used a MJE3055T and also TIP41C transistors but didn't get any results.</p><p>I suspect there is a problem with the coils because it seems I have been doing everything correctly except for the coils.</p><p>Please help! I have to present this project on Sunday, Feb 1.</p><p>Thank you! </p>
when you're running it at 12+ volts does the transistor heat up? Did you try flipping the leads on the primary coil? Did you try running it without a topload?
<p>Thank you very much for the reply! I appreciate it a lot</p><p>Well, I have been using a heat sink with the transistor that could be why it doesnt really heat up. But the heat sink does get slightly hot after turning the circuit on for a while.</p><p>Yes, I have tried flipping the leads on the primary. I also tried the circuit without the topload. </p><p>The problem is that I dont get any voltage or oscillations across the primary.</p><p>But an LED lights up pretty nicely when it is connected in the place of the primary coil, i.e. to the positive rail and collector. So i assume that the transistor is working fine.</p><p>I also tried using a thicker wire for the primary but I still get no voltage across it.</p><p>I would really appreciate your help! Thank you! </p>
<p>The transistor heating up is a good sign and it sounds like the driver part is wired correctly (not necessarily working correctly though), especially with the LED test. Since you're using a slightly higher rated transistor, I would lower the value of the base resistor. Try 10k ohms, maybe 5k ohms (monitor the heating of the transistor when you do this). I'm thinking the transistor isn't being allowed to switch on/off. <br>Have you tried measuring the voltage from the top of the secondary coil?</p>
<p>Thank you so much, Chip!!!! The circuit is finally working!!! I got CFLs and Fluorescent tubes lighting up upto 3-4 inches away from the coils! It seems that once I replaced my old primary with a thicker one and the secondary with a nicely made non overlapping one, all I needed to do was check if the CFL was lighting up when brought near.. but I had failed so many times doing this that I just kept trying to measure the voltage and oscillations across the primary. Just as you said, I should have measured the voltage from the top of the secondary. Later when I was fiddling around with the circuit I found that there were sparks when any wire was brought to close to the secondary. As soon as I saw this I brought a CFL close enough to the secondary and VOILA!!! The lamp lit up! Thank you so much! Wouldn't have been possible without your help! The range has to be increased though.. you have any suggestions? Thank you! ^_^ :D</p>
<p>Oh good! Glad to hear it! Yeah the secondary coil is a critical part. </p><p>To increase the range, make a larger secondary coil with more turns and increase the input voltage.</p>
<p>i can't find awg enameled wire in here(or maybe i haven't searched enough), but i find something that called as &quot;insulator wire&quot;(the wire used in insulator) and the diameter should be about 0.2 mm. Will it work if i used this cable instead of awg enameled wire ?</p>
<p>sorry, i mean inductor wire( the wire used in inductor)</p>
<p>What does a top load function as? </p>
It acts as a capacitor between ground and the top of the secondary.

About This Instructable


397 favorites


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 »
More by Chip Fixes: LED Pong Creative Valentines Gift How to Build a Slayer Exciter
Add instructable to: