A Hand Held Tesla Coil Battery Powered ‘Plasma Gun’

The design for this Tesla Coil is based on the larger battery powered DIY Tesla Coil project but with the aim of getting a much smaller and portable device. A Power Pulse Modulator circuit is used to drive two small high voltage ignition coils wired together in an ‘anti-parralel’ configuration. The output is rectified and used to charge the tank capacitor of a small spark gap Tesla Coil.

WARNING: This project uses dangerous high voltages!

This project is quite old now. Check out the new, more powerful DIY Plasma Gun!

The device is packed into the casing of cheapo cordless drill from a DIY store. This drill used an 18V battery and comes with a charger which made it ideal for the project. The ignition coil driver circuit used takes a direct 12V – 30V input which is connected using the original switch from the drill.

This video clip shows the plasma gun causing a nearby light bulb to light up as if it were a plasma globe.

The high frequency, high voltage from the plasma gun causes the Argon gas in the light bulb to become ionized. This creates streamers that are attracted to the fingers holding it.

The device draws about 6 amps from a well charged 12 V battery which makes the total power consumption to around 72 watts. Unfortunately this low power means the plasma arcs will be limited in size, but since it is hand held that’s probably a good thing. The typical length of the output arcs is between 5 and 7cm

A Multi-purpose power pulse generator capable of driving Tesla Coils and other high power coils. This device is based on the Homemade Tesla Coil project and uses an improved version of the ignition coil driver circuit to generate high voltages.

This unit quite simply can generate high current pulses of variable frequency and pulse width. This unit uses the Square wave frequency generator shown in the DIY Devices section for the main signal source but any other signal source can also be connected to it. The input signal is amplified using an array of nine 2N3055 power transistors (T2) which is capable of switching huge amounts of power.

WARNING: High Voltage is used in this project!

A switch allows power to be sent to external coils for low voltage applications, or the internal ignition coils can be powered for charging a large HV pulse discharge capacitor.

The low voltage circuit in this device is similar to the driver for the Homemade Tesla Coil, but with some important differences. The high current pulses from the Lead Acid Batteries makes the signal generator unstable in the original design. The new version uses a completely independent signal source with its own battery to minimize the interference. There is also an extra buffer circuit to protect the 2N3055 Transistors from voltage spikes caused by the inductive kickback from the auto ignition coils.

All the power electronics are housed in an Aluminum case finished with panel meters, IO ports, and switches. The signal generator circuit is housed in an independent unit with its own 9V battery. This can be connected to the main unit via a shielded cable allowing it to be operated from a safe distance.

The high voltage output from the ignition coils is rectified using some large high voltage diodes (D2) designed for X-Ray machines. The rectified output is connected to a large capacitor (C1) for smoothing the DC output. From the smoothing capacitor an inductor (L1) and an additional ‘de-Q-ing’ diode (D3) have been added to the charging circuit to block the AC ringing from the TC primary coil from reaching the the smoothing capacitor. These also help to protect the the rectifier from short circuits, arcing currents and possible back EMF or transients.

The connectors used here are just standard banana types. They are not designed for high voltage use and will therefore leak a little energy by ionising the air nearby.

The main high voltage front panel on the box has sockets for HV DC output, an internal HV pulse discharge capacitor, and an internal spark gap. This allows the high voltage circuits to be configured in a number of different ways without having to re-wire any internal components.

The image on the right shows how the panel is wired to drive a Tesla Coil. The spark gap can be adjusted using a handle on the side of the case. Depending upon the resonant frequency of the TC being driven, it may be necessary to adjust the capacitance. This can simply be done by adding more capacitors in parallel, or using a separate one.

This image shows the interconnected outputs of the ignition coils. The ignition coils are wired in parallel to give a higher output current.

All the high voltage cabling inside the box is placed inside flexible plastic tubing for added insulation. You can see here that the low voltage connections to the ignition coils are also covered with tubing for added protection.

The case is grounded by connecting a thick wire to a long metal spike driven into the ground. All of the ground connections for the internal circuits are also connected to the case.

Connecting the case to the earth spike is essential when using the device to drive Tesla coils. This is because a Tesla Coil (TC) will generate radio frequency (RF) currents that would otherwise become present throughout the circuit. Without a good RF ground you would probably receive little shocks from the controls when operating a Tesla Coil.

Internal Variable Spark Gap

This new spark gap is made using three spherical electrodes in a high K dielectric casing. The double casing of the spark gap reduces the overall noise and allows the airflow to be doped with other gasses.The anode and cathode are spaced further than the voltage could jump and the third sphere can be moved in and out of the gap via a long glass fibre rod. This allows the spark gap to be adjusted smoothly anywhere between short and open circuit whilst it is active.

A pair of 12V DC brushless fans are installed to improve airflow through the spark gap. This is not to improve quenching, but it will reduce electrode corrosion from Ozone buildup in the spark gap casing. A further filtering capacitor has been added across the fans connectors as this type is sensitive to voltage spikes

Controls

The control circuit used for generating the driving signal is made using a 555 based circuit. This circuit can be found on the DIY Devices Page and is titled Signal Generator with Pulse Width Control. This circuit is housed inside a small hand held box with a 9V battery. It can be connected to the Power Pulse Generator by a jack plug on the end of the cable from the unit. You can buy an advanced version of this signal source here.

Different ignition coils or transformers will have different resonant frequencies. Using this circuit allows the Ignition coils to be tuned and driven at their resonant frequency.

External transformers, coils, or solenoids can also be driven at any desired frequency within the range of the 555 timer. The pulse width modulation capabilities of the control circuit are used for power level control for transformers and other coils. This feature also allows large or small DC motors to be powered with variable speed between 0% and 100%. These can also be tuned to their resonant frequency.

This device is capable of powering a multitude of experiments and is great for any researcher experimenting with pulsed power or resonant applications. You can see experiments we have done with Tesla Coils using this device on the Tesla Coil Experiments page.

DIY Plasma Gun II

The DIY Plasma Gun II is an improved version of a compact, portable, spark gap Tesla coil which can create jets of high voltage plasma and even doubles as a flame thrower! This updated version of our hand held Tesla Coil has been optimized for improved efficiency and gives a larger output than the previous one. It is also now even easier to build! You can find the old version on the original Plasma Gun page. We decided to stick to a spark gap type Tesla Coil for this plasma gun as it is considerably easier to build and more reliable than solid state controllers. We will however produce a solid state version in future.

This page should show you all you need to know about how to make a plasma gun like the one shown here. Hopefully it will also teach you the science behind it so that you will know how it works. Remember that this is a dangerous high voltage project and should not be attempted by inexperienced people.

What does the Plasma Gun do?

This plasma gun is essentially a small battery powered spark gap Tesla coil. Its inteded purpous is more for education, than an actual function. We hope that is is a fun and interesting project and that you will learn something from it. If you make your own plasma gun, please post a picture below!

The plasma is made by ionizing air around the output terminal of the Tesla coil. The high frequency, high voltage electricity is able to form streams of plasma that can be made to spread out, or be directed forward along a flame or stream of gas. This directed plasma channel can actually have a useful function in some industrial processes known as “plasma surface treatment”. When the jet of plasma is directed at a surface such as a plastic bottle, subtle changes will occur in the structure of the material on a very thin surface layer. Typically these changes will make the surface more porous, or easier to print onto.

Anyway, enough of that, we know you really want it just becasue it’s cool, and you want to build your own plasma gun! On to how it’s made…

Warning: This project involves dangerous high voltage electricity!

How it’s made

High Voltage Inverter
For converting the low battery voltage into high voltage for charging the primary capacitor.

This part of the plasma gun does the main power conversion by pulsing a high voltage ignition coil. Pulsing the spark coil will step up the voltage from the battery to about 20kV which is used to charge the main capacitor. This capacitor is later discharged into the primary coil of a Tesla Coil to further increase the voltage.

For this we used a Power Pulse Modulator (PWM-OCXI) as it is really simple to use and will give a really powerful high voltage output from an ignition coil. The PWM-OCXI is considerably more powerful than the PWM-OC10A which was used in the original plasma gun project and therefore improves power throughput significantly. This circuit was mounted in the back end of a cordless drill casing so that the control pots and LEDs were accesable from the back. At the side of the drill casing a small switch was mounted that could be used to switch the circuit on and off. This serves as a safety to power down the plasma gun when not in use.

The power to the ignition coil was fed directly from the drill battery via the original trigger switch, into the L- connector on the OCXI. By connecting like this, the control circuit and its cooling fan stays active between times when the plasma gun is fired. 

It is neccesary to add a high voltage diode to the output of the ignition coil so that a capacitor can be charged. For this, the rubber end of the ignition coil was removed, and the diode connected to the spring inside the tip. The tip was then filled with epoxy resin so that the high voltage would not flash over the body of the diode. This also helps to cool the diode by absorbing heat from it. The cathode wire is left protruding from the resin so that it can be connected to a small inductor. This inductor serves as a choke to protect the diode from the high frequency currents in the primary circuit.

Primary Tank Circuit
For storing energy in a resonant circuit to be rapidly discharged in pulses.

The primary tank circuit here consists of a high voltage capacitor, spark gap, and a coil of wire (an inductor) known as the primary coil. When the capacitor becomes charged to a high enough voltage, the air between the terminals of the spark gap will break down with a loud bang and a bright flash. During this very brief flash, the energy in the capacitor will be moved into the primary coil and then back again over and over at about 1,000,000 times per second! This frequency of 1MHz is determined by the sizes of the capacitor and the coil and is know as the resonant frequency. The resonant frequency of this inductor capacitor combination can be calculated as follows;

Primary Circuit Resonant Frequency

f = 1 / (2 x π x √(L x C)) = 1,000,000 Hertz

Where f = Resonant frequency, L = Inductance and C = Capacitance

The value of the capacitor is fixed, and the inductance of the primary coil is determined by its size and the number of turns of wire used to make it. 

The capacitor used was chosen for improved efficiency over the ceramic capacitors used in the original Plasma Gun. By using a quality polypropelene capacitor with a low ESR and low ESL, the losses in the high frequency resonant circuit are reduced significantly. This means more awesome sparks!

When choosing the values for the components a number of factors must be considered. Some factors are fixed, while others can be varied. The table below details some of the points which must be considered.

Secondary Coil
Self resonant circuit which magnifies the primary voltage so that it can discharge as plasma streams.

By using 0.25mm wire there is a reasonable amount of copper for conducting current through the coil but due to the small size, only 750 can be fit onto the coil. Without a discharge terminal (topload), the resonant frequency is around 1100kHz. Such a high frequency introduces losses so we can reduce this frequency by adding a larger topload. The toroid used brings it down to a more reasonable 900kHz.

Due to the high electrical stresses, it is important to insulate the coil well with multiple layers of varnish. Although this introduces more dielectric losses, it is essential for preventing sparks flashing over the surface of the coil and for protecting the windings.

Breakout Electrode
For concentrating the electrical discharge in a focused place.

By using a large topload, the electrical field is spread over a large area and will not break out in to arcs until the voltage is very high. While this is advantageous for increasing arc length, it also increases the chances of the arc discharging back towards the coils. The breakout point creates a localised area of intense electric field which will ionise the air more easily and force the discharge away from the end of the plasma gun.

The electrode is fitted with a pipe so that gas can be ejected from the the tip. Some gasses such as Argon or Carbon Dioxide will ionise more easily than air. When ionised it will provide a conductive path, allowing the plasma to reach further from the coil. If butane is used as the gas, it will ignite and also conduct the electric currents. One difficulty with this is that as the arc length increases, it lowers the resonant frequency of the secondary coil causing it to drift away from the resonant frequency of the primary circuit. 

	PARTS LIST: You can buy most of the parts from us directly. You will also need other parts such as the drill. Below is a list of parts available in our shop.
	Power Pulse Modulator (PWM-OCXI)
	1000uF Power Capacitor
	HV Pulse Capacitor (20kV, 10nF)
	HV Spark Coil
	HV Diode (30kV, 100mA)
	Choke (390uH)
	Small Bolt (for choke core)
	Adjustable Spark Gap
	Silicon Cable (for primary coil and other wiring)
	Secondary Coil
	Toroid
	HV Insulators

Tuning
Precise tuning of the resonant circuits for max output.

There are two resonant circuits in the Tesla coil part of the plasma gun which must be tuned to the same frequency. If the frequencies are not matched, the energy transfer will be very poor and your plasma gun will be little more than a noisy spark gap. The secondary coil’s resonant frequency is pretty much fixed. It is possible to make small adjustments by changing the size of the topload, but this is not very practical to do. Instead, it is simpler to choose a primary capacitor, and then adjust the number of turns of the primary coil to get the right resonant frequency. This can be done with a little calculation and then trial and error, but can be quite time consuming.

We used a signal generator and osciliscope for tuning the plasma gun, but it is possible to do it with a little circuit such as a Telsa Coil Tuner although it is not easy. Even after tuning, you may want to tweak the number of turns on the secondary coil to achieve maximum output. When tuning the secondary, keep it away from yourself or other objects as the proximity may alter the resonant frequency.

Once tuned you can also adjust the Power Pulse Modulator so that you get some good resonant charging of the capacitor. At certain frequencies the system will be more efficient o by slowly adjusting the frequency when it is running, it is possible to find the best setting. While making the adjustments, the spark gap firing rate is observed until a setting is found where the maximum firing rate is achieved.