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A DIY Tesla Coil

Tesla Coil

DC Powered with Plasma Output

The aim of this design was to get the highest voltage (or longest arcs) possible from a single self contained unit.

NEWCheck out the new 1kW Tesla Coil!

 

 WARNING: High Voltage Device!


This coil operates from 12V or 24V SLA batteries. A pair of car ignition coils are used to provide around 20kV for charging the capacitor bank. The ignition coils are driven by a variable frequency square wave from a 555 timing chip and four large transistors (2N3055).

 

Battery Powered Tesla Coil Input Voltage 12 - 24V DC
Power Consumption 250W Max
Max Arc Length 25cm
Output Voltage (approx) 250kV
Primary Transformer 2 x Car ignition coils in parallel - 20kV
Capacitor MMC 20kV
Spark Gap 5x 6mm pipes, Variable
Primary Turns 4.5 (Tuned)
Secondary Turns 850
Secondary Height 40cm
Secondary Width 5cm
Topload 10cm Sphere
Special Features


Plasma / Flame discharge terminal
Battery powered
Fully portable
Variable coupling
Basic power management

A pipe from a hole in the top of the sphere and down the inside of the secondary coil is used to supply gas to form a type of plasma electrode.

Plasma FlameUsing Butane gas and air, a blue flame can be used as an interesting discharge terminal. The heated CO2 emissions provide a low pressure channel to conduct the electricity more easily than air. This produces a large plasma column above the flame. At certain spark gap discharge rates the plasma column can be made to resemble a stable double helix formation. Small quantities of other gasses such as neon or helium can be mixed with the butane to produce slightly different colours and effects. The table below should help you find some of the components needed for this project.

Plasma spring

Component
Max Voltage
Source
Ignition Coils
~20kV
Capacitor Bank
20kV
HV Diode
30kV
Power Transistor
400V
Neon / Helium
n/a
ST Gas
Control Circuit
n/a

More Plasma Photos

 

 

MMC Capacitor Capacitor Bank - The capacitor used in this project was made by combining a large number of lower valued capacitors. By connecting smaller capacitors in series the overall voltage they will tolerate is increased. To obtain a higher storage capacity (capacitance) the capacitors can be connected in parallel. This type of capacitor bank is known as an MMC (Multi Mini Capacitors). The next version of this project will use specially designed large pulse discharge capacitors. These capacitors can be more efficient than an MMC, but they can be expensive and hard to find.
Old Ignition Coil Primary Transformer - Ignition coils (Induction coils) obtained from a scrap yard are used for this design. The old ignition coils provide a very cheap way of generating a high voltage for charging the capacitor. The voltage increase in an ignition coil is not determined by the turns ratio like in normal transformers. The secondary voltage depends upon the rate of change of the current in the primary coil. Older ignition coils such as ones from a scrap yard may not work as well as new ones. Over time the insulating oil inside the casing becomes less effective and can lead to internal arcing. This can damage the transistors and the control circuit, rendering them useless
2N3055 Transistors on Heatsink Control Circuit - The control circuit is based on a simple oscillator provided by an NE555 timer chip. The square wave pulses are sent to a set of four 2N3055 power transistors mounted on a large heat sink. These transistors can switch a good amount of power quite quickly, but they can be sensitive to voltage spikes caused by feedback in the circuit, or faulty ignition coils. The Ignition coil driver circuit shown below shows how the signal from the 555 chip is pre-amplified, so that the large transistor array can be driven effectively. Using 2N3055 transistors in this way is not ideal, but it is what we had available at the time for the project. Modern IGBT transistors are much more effective and less prone to failure from voltage spikes.

Ignition Coil Driver Circuit Diagram

 You can buy a more advanced version of this control circuit in our shop.

 

The output from the ignition coils is rectified (converted to DC using diodes) so that can charge the capacitor bank C1 shown b elow.

Tesla Coil Schematic

Primary Coil

Coils - The primary coil is simply made from 2mm enameled copper wire, wound around a plastic stand. There are six turns in total, but the connection is made at about 4.5 turns when tuned. The secondary coil is wound from 0.4mm enameled copper wire around a plastic drainage pipe.

Safety - Attached to the capacitor is a short circuit switch that is activated by a long plastic handle. This is used to make sure the capacitor is fully discharged, and cannot recharge whilst making any manual adjustments. There is also a switch to isolate power from the ignition coils that is activated using a insulating pull cord.

Topload showing inner tubing

Special Features - This project has several extra features compared to a common Tesla Coil. The topload sphere has a small hole to allow gas to be emitted. A 5mm plastic pipe runs down the inside of the secondary coil, and out of the plastic base.

Plasma and Arc Photos

This allows the gas to be piped in, without interfering with the normal operation of the Tesla Coil.

High Quality Neon and Helium

Future Developments - This project is currently being upgraded. The new design aims to achieve a higher power throughput. By using more ignition coils in parallel it should be possible to increase the size of the spark gap, or to fire it more rapidly. New ignition coils will used instead of the second hand ones for improved stability. The new design also incorporates voltage and power monitoring features. It also has a neat metal finish and multiple outputs so that it can be used as a multi purpose portable high voltage power supply

Click here to see the new project

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