3

REGULAR

Direct From Shenzhen

Right

We only

managed to

secure the coil

by taking the

glue to the edge

of the board

DIRECT FROM

SHENZHEN

T

Make music with lightning

Tesla coil

speaker

By Ben Everard ben_everard

he basic principle is very simple:

an audio signal goes in, it’s

amplified, and then sent to a

wire that’s wrapped a single time

around a large coil. This single

wrap is a rudimentary primary coil

and the varying electrical flow in this (being created

by the music signal) creates a much larger voltage

in the secondary coil. This secondary coil is finished

with a loose wire that sticks into the air, and a

sufficiently large voltage is created in the secondary

to produce a spark. This spark heats the air around

it, so as the spark comes and goes with the pulsing

electrical current, this heating causes a vibration

in the air. This vibration is the same frequency as

the audio signal going in. In other words, it’s an

elaborate speaker system.

The tesla coil speaker – also known as a

Zeusophone or a Thoramin, after the Greek god

of lightning and the Norse god of thunder – is

widely available in kit form from direct-from-China

electronics sites. We got a kit from Yi Ma Trading

Company Ltd on Ali Express, though identical kits

are for sale elsewhere. Our test kit cost just £4.96,

including postage.

Our kit came as a PCB and a handful of through-

hole parts. The instructions were in Cantonese,

but it was easy enough to follow along as all you

really need to know is which part goes in which

holes in the PCB, and they were labelled in English

on the board. There are heat sinks for two power

transistors, but again, these were easy to attach.

We’ve seen some similar kits advertised as coming

with thermal paste, though ours didn’t, and it

doesn’t get very hot under moderate use.

The only thing that the kit didn’t come with was a

power supply. It takes a 15-20 V barrel adaptor (the

same shape as an Arduino Uno). This can also be