Building the Poor-mans Mini Tesla Coil ( Slayer Exciter)

A slayer exciter is basically a small solid state tesla coil, usually a one transistor design. The circuitry for it is simple. One of the first things anyone who has built a joule thief will notice, is that the circuitry is very similar. The biggest difference is that the small transformer or inductor has been replaced with a primary/secondary tesla coil configuration, and that the feedback is capacitively coupled. (There is a good abount of capacitance between the 'top' of the coil, and ground.)

There are many awesome thing these exciters can do!
they can:

► WIRELESSLY Light up:

neon lights!-----------------------------------------(several feet away)
florescent tubes!----------------------------------(within about a foot)
CFL's!-----------------------------------------------(within about a foot)
EL wire---------------(it does not work well for me. If anyone tries it, please tell me your results!)
LED's!-----------------------------------------------(across the room if done right)
and even small incandescent lights! -------(with an L3 coil)
paper with pencil markings -------------------(before it catches fire!)

► Burn and ignite:

candles
wood (pencils)
human flesh (now my fingers smell burnt)
paper

► Destroy:

crappy / half dead LED's
bacteria
sensitive electronic equipment (phones, computers, SD cards, CD's, blu rays, flash drives)
someone else's stuff

► Create:

ion wind motors
the coolest lantern or light on earth
fires
plasma cutter

►Make following electronic equipment go crazy:

calculators
watches
digital clocks and alarms
devices with capacitive touchscreens (PlayStation VIVA, smartphones, feature phones, tablets)
UHF remotes

► Transmit wacky sounds (loads of EMI) to:

AM radio
FM radio
shortwave radio
HAM radios possibly
TV interference

Here is how to make a my version of the more powerful exciter (These videos were made awhile after this intructable, so the only issue with it is thermal management.)Please do not get the instructions in this video confused with the instructions for the later TO-92 one in the further steps. Different bias resistor values should be used for either of these 2 versons.

Step 1: A Rundown of My Experimentation

I did modify the circuit a LOT before I was happy with the results. Sadly, I did not take pictures of my circuit on the breadboard.

The first picture show first circuit. I could not get to work.

The second picture shows my first working design. I chewed through many transistors, and it was not very stable, but it worked.

In hopes for better performance and reliably, I tried a darlington pair. It put out about the same amount of power, but did not kill my transistors. I believe this is because it increased the gain and the feedback from L2 was enough to sustain the oscillation. I think this is because it did not latch up and pop my transistors.

I realized after running the circuit for awhile that I wired it wrong on my breadboard but it worked anyway. I decided to "fix" it, and ended up burning out my last 4401. From then on I had to resort to 2n3904's. This darlington pair test was inconclusive due to my mistake of not having the collector from the first transistor connected to anything. I learned that if it ain't broke, don't fix it :P

I finally decided to revert to my original circuit, except this time with all 3 remaining 2N3904's all in parallel. (collector to collector, base to base, emitter to emitter.) This worked exceptionally well, and I haven't killed any transistors since then! Now, I even get plasma shooting out the end! If you decide to build this, use that configuration, but use more powerful transistors, like 2N2222's or 2N4401's. They can handle more current.

[UPDATE, March 2014] Later on I then decided to use a MJE3055 transistor instead of the weak TO92 transistors, and started to get much better performance. I upped the voltage from 9V to 12V, and replaced the 1Mohm resistor for a 10K resistor. You can get the instructional details in the video.

[UPDATE May, 2015] I have now began work on a MOSFET version of the slayer exciter, and with 50V and a computer heatsink, I can achieve results that border a small SSTC!!! (Solid State Tesla Coil) Unfortunately the complexity of the circuit did increase, due to the need to drive the gate of the FET with buffer to allow fast switching. Luckily it is ultra stable when tuned correctly, and can deliver much more power with more supply voltage. I increased the size of the heatsink compared to what I used in the first slayer exciter video, and have active cooling fan giving some airflow. Now I can let it run indefinitely at 24V and beyond! :D Note: The topload is still critical, if it is too large, performance will decrease. Also I can draw up to 3 inch long, incredibly hot arcs, and get corona that is about an inch long!!! I have even managed to "burn out" a screwdriver from the inside-out! Where the shaft is encapsulated in clear plastic, the plastic began to experience dielectric breakdown and began to melt, and eventually the electricity burned a carbonized hole all the way through the plastic to my fingers, Ouch! The electricity must really love me! :P.

Step 2: Dangers

The output of the Slayer Exciter is high frequency high voltage. (I measured about 100KHz for those interested) Although the arcs are small, it's still able to catch things on fire and give you (admittedly very small) 3rd degree burns! These are safer than many other high voltage projects, and thus make a good starter projects along with static electricity and Van De Graaff generators. Just make sure to exercise caution when fiddling around with this circuit.

Also, Obviously, this thing is a fire hazard. I have managed to catch matches, pencils and wood, candles, and other flammable materials on fire. Without proper precautions, safety measures, and supervision, that can lead to an uncontrollable fires. If you plan on attempting that, do so far away from flammable furniture or housing, and materials and gasses.

Remember: I do NOT express any responsibility or liability of any kind, explicit, or implied. If you destroy your own stuff or someone else's stuff, do not come crying to me!

Step 3: Things You Will Need:

700-800 feet of enameled magnet wire.

NPN transistor (if you plan to buy them, buy them in bulk. Likely, you will pop a few while working on the circuit. I recommend a high power transistor, they just work better.)

Here is a list of the transistors that should work. The one's I have used are italicized along with others who say that they work.
- TIP3055 (works well @ 12V, just make sure to use a heat sink)
- MJE3055T (works just as well as the TIP3055 does, and has proven to be the most reliable.)
- 2N3055
- TIP31C
- TIP41
- 2N3904(needs least two of them in parallel for reasonable output)
- PN2222 (variant of 2N2222, just in a newer case, the TO-92)
- 2N4401
- unlabeled transistors from a camera flash circuit
- many others. If you know of one that works well, post it in the comments!

clean PVC pipe to wind the coil around (I used a paper towel roll, but this is not ideal, especially in humid environments.)

PCB to solder everything to (or a breadboard for temporary builds) (I do not recommend sloppy builds, as this is high frequency AC stuff we are dealing with. So the sloppier the thing is built, and the longer the wires connecting things are, the more prone to failure it will be and the worse it will perform. Keep wires short, and take the time to build the circuit carefully and be neat when winding the L2 coil.)

Step 4: Tools Required:

Good soldering iron w/ solder and flux (if you plan on making this permanent)
variable power supply with current limiting options
L2 winding jig (Recomended)
Camera (optional)

Step 5: Optimal But Recommended:

Small signal diodes

many LED's of various colors and types

a few fluorescent bulbs (larger ones will glow brighter.)

christmas lights and other flashlight bulbs w/ several feet of wire

junk parts to fry

electronic equipment to drive nuts! (radios, calculators, remotes, and someone else's phone and computer)

candles and things to destroy!

Step 6: The All-important Schematic and How to Build It. (small TO92 Version)

There is not much to this circuit. Above are all the graphics and pictures. After you gather all your materials, take your transistor and wire it up. (Note, these instructions ONLY apply to the schematics shown below. NOT the video version of the circuit using a MJE3055T.)

1) Connect the emitter of the transistor to the common or ground.

2) Connect the base of your transistor to one end of the resistor, as well as to the bottom of the L2 coil. (this creates the differentiated negative feedback, which allows the transistor to oscillate.)

3) This is a little tricky. I have made a graphic to illustrate this step visually. If the winding's of your L1 coil run around the L2 coil in the same direction, (where both winding's run either clockwise or counter-clockwise), then the end closer to the top connects to collector. If the winding's go against each other, (One goes around counter-clockwise while the other is clockwise and Vise-Versa) then the bottom end connects to the collector of the transistor. If you have this incorrect, you may damage your transistor. If you are not sure when about to apply power, use current limiting, or a low enough voltage.

4) Connect the other end of L1 to the positive rail.

5) (Optional) Connect the negative end of the LED's to the base. (They are wired in series, so test them to make sure both light up when connected to a 6V power supply w/ current limiting resistor.) The side with the flat ridges or longer terminals if they are brand new LEDs should face the transistor such that the terminal nearest the flat ridge is connected to the base

6) Now attach the capacitor between the positive and negative rail. I found the best type is a high value film or ceramic cap, or the largest electrolytic capacitor you can source. Now the circuit is done, click the next step for testing and troubleshooting.

Step 7: Testing and Troubleshooting (TO-92 Small Slayer Exciter)

Here is the troubleshooting guide for the first variant of the circuit I built, it is for the versions using a 2N2222, 3904, 4401, etc:

It may be tempting to connect your circuit directly to a 9V power supply or battery, but this is a bad choice. That's how I burned out most of my transistors during my experimentation. After you have built your circuit check over everything and make sure it is wired correctly, and if it was done on a PCB, make sure there are no solder bridges.

First, after paying close attention to the polarity, power the project with 4.5V-5V, or 3 AA batteries to the rails and see if the leds light up, or if you can get a neon lamp to glow next to the output L2 coil. Keep a close eye on the transistors, and make sure they stay cool to the touch. If they are becoming really hot, with no neon bulbs glowing, then you have a problem. If it all checks out, increase the power. At 6-7.5V (or about 4-5 AA batteries in series), I found that the circuit can can output enough radiant energy to make a fluorescent light glow. Adjust the number of winding's for the best performance. I found 9 turns on less than 9V works best. Now, power the exciter with 9 volts, from a power supply or 6 AA batteries in series. (avoid using a 9V battery for this circuit, especially a heavy duty garbage battery!!!! They will die quickly and have a really high ESR). If it seems to work, hold it on for a few seconds. Keep your fingers on both the kill switch and the transistors. Make sure they do not get hot.

**Failure modes of operation, and how to fix them:**

IF the transistor gets HOT, and it does not work well or at all judging by the neon lamp test:

90% of the time, this means that either:
- A) The value of the bias resistor is too low, (try a higher value resistor, maybe 4.7k-20k)
- B) The polarity of the L1 coil may be incorrect. (try switching the polarity)
- C) The number of windings is way too low, it should be more than 3 at least.

IF the transistor is COOL to the touch, and does not work well or at all judging by the neon lamp test:

The polarity of the L1 coil incorrect. (try switching the polarity)
The bias resistor is too high a value. (try less than 1 MEGohm.)
You have incorrectly built the circuit, (check and recheck the wiring)
Too many turns for the L1 coil causes poor performance (try less windings for the primary)
You screwed the pooch and killed your transistor

IF the circuit works, and the transistor is getting warm, borderline hot, but still does not function as well as mine:

Adjust the number of turns on the primary, or L1. I find 9 turns work will for less than 9V operation.
Adjust the bias resistor value, if it is too low, the transistor gets excessively hot. Too high, the circuit does not work well.
Notice that the version shown in the video uses a larger transistor, not the small TO-92 ones:
- You have the cravings for LOTS of radiation, so try a BIGGER and BETTER transistor!!!!!

Using transistors of higher current gain and power dissipation will be better.

Step 8: Testing and Troubleshooting (Larger TO-220 Version Shown in Video)

Here is the troubleshooting guide for the version of the slayer exciter shown in the video this guide is for the more powerful 3055, TIP31C, TIP41, etc.

After building the circuit and realising it does not work, first, make sure you power supply can deliver 12V at 1.5A minimum for best performance. I found that the circuit will draw as much as 3A at 20V, so if you plan on using such high voltages, make sure the supply can deliver the current.

It may be tempting to connect your circuit directly to a 12V 1A power supply or SLA battery right away, but this is a bad idea. After you have built your circuit check over everything and make sure it is wired correctly, and if it was done on a PCB, make sure there are no solder bridges. First, after paying close attention to the polarity, power the project with 6V, or 4 AA batteries to the rails and do the neon lamp test. Keep a close eye on the transistors, and make sure they stay cool to the touch. If they are becoming really hot, with no neon bulbs glowing, then you have a problem, and you may need to add a really big heatsink. If it all checks out, increase the voltage to 12V with a lamp in series with the power supply if it is not current limited to 2A. (as is the case if you use a SLA battery). It should still work, but perhaps poorly. Adjust the number of winding's and the bias resistor for best performance. I found 3-5 turns for 12V works best. (For this variant, DO NOT EVER EVER use a 9V battery, especially a heavy duty garbage battery!!!! They will die quickly, do not store much energy, have really poor power density, cannot deliver more than an amp, and they are just really bad. I would not be surprised if the battery leaks or explodes after using it for this circuit.). If it seems to work, hold it on for a few seconds. Keep your fingers on both the kill switch and the transistors. Make sure they do not get hot.

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**Failure modes of operation, and how to fix them:** IF the transistor gets HOT, and it does not work well or at all judging by the neon lamp test:

This 90% of the time means that either:
- A) The value of the bias resistor is too low, (try a higher value resistor)
- B) The polarity of the L1 coil may be incorrect. (try switching the polarity)

IF the transistor is COOL to the touch, and does not work will or at all judging by the neon lamp test:
- The polarity of the L1 coil incorrect. (try switching the polarity)
- The bias resistor is too high a value. (try less than 10k.)
- You have incorrectly built the circuit, (check and recheck the wiring)
- Too many turns for the L1 coil causes poor performance (try less windings for the primary)
- You screwed the pooch and killed your transistor

IF the circuit works, and the transistor is getting warm, borderline hot, but still does not function as well as mine:
- Adjust the number of turns on the primary, or L1. I find 3-5 turns work will for 12V operation.
- Adjust the bias resistor value, if it is too low, the transistor gets excessively hot. Too high, the circuit does not work well.
- Try a different transistor, or one from a reputable brand, like Linear Technology, STmicroelectronics, Texas Instruments, ON semiconductor, or the ones you find on Jameco, radioshack (now bankrupt :( ) Digi Key, mouser, etc. Avoid the too-good-to-be-true deals on eBay. Often you will get hung-wan-low quality garbage, or old used and recycled transistors that have been cleaned up and the old part number of an inferior transistor scrubbed off and a new one printed on. Obviously you do not want that garbage.
- You have the cravings for LOTS more radiation and EMI, try build a proper tesla coil! That is the next logical step up! :).

Introduction: Building the Poor-mans Mini Tesla Coil ( Slayer Exciter)