High Voltage generator
Using a TV flyback transformer
Introduction
This HV generator is able to generate a pulsed high voltage which is high enough to draw sparks of more than one cm!
All you need is a TV flyback transformer, two 0.47uF/250V capacitors a diac, a 600V thyristor and some standard resistors/capacitors.
I use a spark gap built with two sewing needles: listen to the sound of the generator in action!
Tip for the real freaks: a nice sound to use as a door bell?
Picture of the generator in action:
Circuit description
The circuit works as follows: (see also schematic below)
The 1N4007 diodes and the 0.47 uF capacitors build a voltage doubler: both capacitors are charged
to the peak mains voltage of about 300 V. As both capacitors are put in series, the rail to rail voltage
will be about 600 V; a good starting point for a primary voltage!
The 2k2 resistor at the input acts as a current limiter.
When the capacitors are charged, the small 100 nF capacitor will be charged through the 1M resistor.
At about 30 Volts on the 100nF cap, the diac will strike: the thyristor will be triggered.
All charge in both 0.47uF capacitors will be discharged through the Flyback primary winding,
this will result in a high voltage peak at the secondary.
When the capacitors are discharged and the mains voltage sine becomes zero, the thyristor switches off
and the cycle will start over again.
High Voltage generator schematic
For the primary I just picked two primary terminals of the transformer which were connected according to my
mutimeter. You can also make your own primary by wrapping about 30 windings of wire around the core.
The thyristor and diac are not very critical; just make sure the thyristor has 600V rating or more.
Also the dimensioning of the 1M/150k/100nF is not too critical. Here it is important that the 30 V trigger voltage
of the diac is reached after the mains capacitors are fully charged to 2 x 300 Volt.
The diac can be replaced by a small neon lamp (without series resistor), these lamps trigger at about 70 Volts
but act about the same as a diac
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components at the
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