High Voltage Fun
866 views · Published 26 April 2013 · 2:02 · Indexed 11 October 2026
Channel: Paul Nathan · 2013 · Science & Technology
Here I got a 240 to 12V centre-tapped transformer to resonate using a transistor. The base of the transistor was controlled via one half of the split secondary coil that acted as a sense coil. So when the magnetic field on the primary collapsed, it sent a spike to the base of the transistor (NPN TIP 31C) via induction on the sense coil which then sent a burst of current through the other half of the secondary which upon collapse induces current into the primary and the cycle continues at the system's resonant frequency. This was run off a 21V DC power supply and was drawing about 0.8A. The spark length reached around 6mm max. which, assuming standard air, implies a voltage of 19.8kV - rather dangerous stuff :-))) As you can see, I was easily amused by this.... The buzzing sound you can hear is not a warning buzzer but is actually the transformer core buzzing due to magnetostriction. The changing magnetic field is so strong that it squeezes and expands the iron core such that it makes sound! This is the same phenomenon that gives you the high pitched whine from a charging camera flash circuit.
