Saturday, 13 August 2011

Tesla coil; resonance demonstration.

Today i ve nothing new project to post except to just wanna explain my recent demonstration of resonance and wireless energy transfer using mini Tesla coil i ve built recently.

Resonance is the very fundamental concept that enables the functions of most current ubiquitous wireless devices. Radio receiver, handset, radar,satellite and televisions are all dependent on this principle.

Resonance occurs when the frequency of the energy supplied to a system is the same as the natural frequency of the system. At resonance, the system will receive most energy from the energy source, and tend to damage itself, unless controlled.

In Tesla coil, like no other conventional transformers, the secondary coil resonates with the primary coil. Hence, most of the energy supplied by the primary coil will be intercepted by the secondary coil and this in turn increases efficiency. To achieve this, of course (by the definition of resonance) the natural frequency of the tank circuit formed by the capacitor and the primary must be the same with the tank circuit formed by the air-earth 'capacitor' and the secondary. Since the secondary coil tends to damage itself with excessive energy being transferred into it, therefore a spark gap is made at the primary coil to release the excess energy.

Since resonance occurs at the same frequency of energy source and receiving system, i wondered whether the energy received by the secondary coil can be transferred further to a similar system with same or almost same natural frequency. Due to this, i constructed a third coil , which is having same diameter, length, wire diameter in order to make its natural frequency as close as possible to that of the secondary coil. The following diagram shows the secondary coil and the third coil.

Both coils, secondary and third coils.

Current setup. Its the same i ve been using before. The 275ml bottle wrapped in aluminium foil is my homemade capacitor. I chose this one cuz it gives longest spark on the secondary ie it enables the primary ( the yellow wire) to resonate with the secondary.

The system, without the third coil. A strand of corona was pulled by using screwdriver. Its about 1.5cm length.

When putting the third coil in the vicinity of the secondary coil, it resonates and due to this, a 0.7cm can be observed between the screwdriver and the breakout point. How do i prove that it really resonates and not receiving energy from the yellow wire ( the primary coil)? I removed the secondary winding away, and then tried powering the circuit again. And no spark was observed at the third coil. This proves that it really resonates with the secondary coil.

How the resonance is applied in telecommunication? Well, i guess u can contemplate over the experiment. The secondary is the transmitter of the energy while the third coil is your 'handset', television, radio receiver and any type of wireless devices. The differences between resonance observed in my demonstration and the resonance in real application in wireless devices are that the power is transferred at larger distance and higher band of frequencies, and the power is not only bringing itself, it also brings signals ( it is modulated )that will be translated and amplified into perceivable video and audio signals.


  1. You removed the paper. But now you do your experiment on a wool carpet?... Beli mejalah.
    Lagipun wool carpet ada cas statik.

    Coil tu gulung sendiri ke? Sdra mmg rajin hehehe

  2. Yup, the coils were hand wound. It took me about 2hours for each coil. (-.-') so tiring! but it worth a hands-on experience.