High-voltage experimenters have been using automotive ignition coils to generate impressive sparks in the home lab for decades, and why not? They’re cheap, easily obtainable, and at the end of the day, producing sparks is literally what they’re designed to do. But that doesn’t mean there isn’t room for improvement.
In his latest Plasma Channel video [Jay Bowles] revisits this classic experiment, bringing to bear the considerable high-voltage experience he’s gained over the last several years. Building on an earlier setup that used a single Honda ignition coil, this new dual-coil version can produce up to 60,000 volts and is driven by a cleaner and more reliable circuit based on the iconic 555 timer. A pair of potentiometers on the front of the driver can adjust its square wave output from 1 to 10 kilohertz manually, while a commercial Bluetooth audio receiver tied into the 555 circuit allows the output to be modulated by simply playing audio from a paired device.
As [Jay] explains, wiring up a basic ignition coil is very simple. Usually there are just three terminals: the positive and negative inputs, and a high-voltage output. But in this case since he’s driving two coils, he’s actually wired one backwards. Bolted into a nice acrylic holder and with banana plugs to provide the roughly 18 – 25 VDC input, you’ve got a compact and reliable high-voltage source. The driver itself is an evolved version of a circuit he’s used in past projects, and beyond the addition of the Bluetooth audio input, now features a snubber circuit to help keep the 555 from getting cooked.
So what’s the result? Well a lot of gorgeous sparks, for one thing. But with audio playing through Bluetooth, the arc between the dual coils will act as a plasma speaker. The output is clear, but not terribly loud. According to [Jay] that’s because the ignition coils weren’t meant to be driven at such high frequencies, with the result being reduced output voltage. But as demonstrated at the end of the video, it turns out there’s more than one way to get audio out of this rig; with an antenna connected to the output of the coils, the system becomes a radio transmitter.