A Jacobs ladder is an arc that forms between two upright electrodes that are wider at the top. The arc starts at the bottom and rises with the heat of the arc becoming progressively larger until it “breaks” at the top. It then reignites at the bottom to start over again.
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This is my earliest use of electronics to drive a solid state Tesla coil using SIDAC’s in place of a spark gap. It is a proof of principle coil rather than a big performer. “Continue reading” for more details and photos. Continue reading
The second version Tesla Coil 4-inch in diameter is driven by 4 microwave oven transformers (MOT’s) and puts out 4 foot sparks.
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A Tesla Coil is a high voltage device that makes big sparks. It was pioneered by Nikola Tesla over 100 years ago. This is an introduction to my many Tesla coils and their effects.
More technical explanation: In its simplest form it is an air cored transformer driven by discharging a high voltage capacitor (eg 10 kV) through a few of the primary turns. A resonance occurs with this capacitor and the few primary turns (eg 100 kHz). This induces current in the tall secondary with many turns (eg 1000). A high frequency resonance of the same frequency occurs between the inductance of the tall secondary coil and the capacitance of a rounded metal object (typically a donut shaped toroid). A very high voltage (eg 200 kV) results in electricity (streamers) directly into the air or sparks to nearby objects. Best results occur when the number of primary turns makes both resonances equal in frequency.
A Tesla coil such as the one above with sparks of 8 feet equates to perhaps 250,000 Volts. It is very hard to measure this voltage directly.
A simplified circuit diagram of one of my Tesla coils is shown below with various filter circuitry and safety spark gaps to prevent the very high voltages from wreaking havoc with the lower voltage side. It uses 4 microwave oven transformers (MOT’s) driven by a variac. These take 240 V AC mains and supply about 8 kV to the primary coil, capacitor and spark gap. This circuit is resonant at about 100 kHz and drives the secondary coil and toroid which are resonant at the same frequency.
Tesla coil in a briefcase. This is my latest easily portable mini coil which gives 2-3 inch sparks. These are great fun and are generally safe due to the low power.
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My first Tesla coil using a neon sign transformer with a ferrite cored secondary giving 2 inch sparks. I developed this idea with an old transformer from a dumpster which in retrospect was an old unpotted NST (neon sign transformer). I used a single static gap with a 12 inch ferrite cored coil of 11 primary and 100 turns secondary giving 2 inch sparks with 26 small ceramic capacitors with 2 strings of 13 x 10 nF at 2.5 kV each. It ran nicely for about 20 years! This photo is a mock up with most of the original parts.
I developed this from my first “Tesla coil” discovery while doing a spark spectroscopy project. Years after I made it I heard that Tesla had beaten me to that discovery by quite a few years! This photo is a mock up with most of the original parts.
It now has new life as a Jacob’s ladder.
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Photo Date: Jan 19, 2003
The SSY1 laser was used as a range-finder laser on an M1 tank as I understand.
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I have held regular Home Open Days where I did demonstrations for people by invitation.
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