Saturday, 9 July 2011

My baby Tesla coil.

I started building Tesla coil by first learning how to build an inverter from DC supply. I found an inverter circuit here made by Joshua D. Wyatt, from this link.

There, he used the inverter circuit to power EL backlights and fluorescent tubes, so the output is about 127 VAC as he claimed. But I want 1kV or more to make at least 1mm purple plasma as Tesla coil usually produce! (30kV is required to make 1cm length plasma). Therefore i use MOSFET IRF 840 as a transistor for high switching rate (also any IRF-named MOSFET will do, such as IRF741 and 630) and also transformer i use before from cracking open a battery charger to step up the voltage to more than 1kV.

Here goes the schematic with specifications following it:
I used:

R1: 100kOhm. Again up to you. Its values controls the duty cycle of the triangular pulses generated at the end of the MOSFET.
R2: 464kOhm or more, up to you ( you experiment it yourself). This resistor controls the frequency so different values produce different sound pitches of the plasma ( it produces buzzing sound depending on its operating frequency)
C1:0.047 microFarad
C2:0.01 microFarad
C3:0.1 microFarad
C4:100 microFarad
Q1: MOSFET transistor N-channel IRF840
T1: step down transformer from battery charger (converting 240AC to 2.8DC). For this project I inverted its function as a step up transformer.

The plasma length is about 2mm maximum, with the output voltage of about 1888V (I think it should be slightly higher since my multimeter couldnt measure it due to its almost broken and internal red light was seen flashing inside! I dont know where the light came from,there is no warning LED there, but my multimeter still survived that thrilling incident).

Here are the photos taken:

Just showing the transformer and red leads ( the plasma producing leads). I hate the circuit since it looks messy on the breadboard ( i hate soldering my projects...haha

The spark is very small, like i said before its 2mm in length. So small, and purple in colour. Cuz this is my 'baby' project before moving into the main one ( i m waiting for my copper wire to arrive to create my own flyback transformer)

Another photo from same angle, booooriiinnggg....

OK, gotta sleep now...bye

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