Plasma Speaker
I decided to create a plasma speaker after I saw that my high school was getting rid of a bunch of old electronics and equipment. Among those were several CRT TVs which I took the transformer and electronics from to make the speaker.
The speaker is capable of replicating sound files as is, including vocals and instruments, through an aux cable and the arc is in the 10s of thousands of volts. All sound in the videos is only from the arc!
Unmute to listen!
Boulevard of Broken Dreams - Green Day
Working Principle
The driving circuit uses a 555 timer running in astable mode (chip designed by a Northeastern alum in the 70s). The base frequency of the timer is set using the potentiometers and is set to outside human hearing range (>20 KHz). The audio source, either directly through an aux cable or from an amplifier first, is wired to the control pin to create a frequency-modulated signal separate from the base signal. The signal is converted into a corresponding square wave and goes to the MOSFET hooked up to the flyback transformer. There are 8-10 rounds of wire wrapped around the ferrite core of the transformer. The transformer then steps up the 12V AC music signal on the primary windings to the kV range which creates the arcs of plasma at a corresponding frequency to the music!
Initial Testing
The initial tests below are with an untuned circuit. Number of windings and potentiometer positions are different for each flyback transformer. A magnetron magnet from a microwave is attached to one of the electrodes on the output of the transformer to see the interaction between the magnetic field and the arcs. To prevent the MOSFETs from burning out, they are avalanche rated and attached to a heatsink. A RC snubber was also attached to the output to protect the MOSFETs.