Stunning Jingle Bells

Idea: Roel Arits (Netherlands)

Christmas is an exciting time, especially when the packages are under the Christmas tree (“that little package on the front left - are the keys to my new Mercedes in there?”). And with this circuit, we increase the voltage a little — up to 30 kV to be precise.

We use that 30 kV to generate sparks. That already looks spectacular in the dark, but in this case, those sparks also play a melody: either "Jingle Bells" or "Mission Impossible." The surprisingly simple schematic is given in Figure 1. (The schematic is available in a larger format for download.)

 

The heart of the circuit is an Arduino Pro Mini. It generates a PWM signal with a fixed duty cycle of 10% (which is actually a normal square wave). This square wave is converted to 12 V and buffered. Then, a high-voltage transformer makes a voltage of around 30 kV, which is high enough to draw beautiful sparks.

A regular square wave doesn't make music yet. That's why the software in the Arduino (which can be downloaded below) varies the frequency at the tempo of the two pre-programmed melodies. The result can be seen and heard in this video by the author.

The structure of the circuit is not critical; only the transformer requires some tinkering. The primary winding consists of 20 turns of 0.7-mm copper lacquer wire on the end of two abutting ferrite rods with a diameter of 10 mm and a length of 80 mm. Pressed tightly together, these two rods fit snugly in the opening of a ready-to-use, 16-kV coil that acts as a secondary (see Figure 2). That coil can be bought here; it is also very resistant to the 30 kV of this circuit!

 

At the time of writing, it is nearly 30º for editing. It is hardly a temperature to get into Christmas mood. Nevertheless, in the November/December issue of Elektor, we come back to this circuit in more detail — right in time for the New Year's holiday.