40kV DC high voltage supply
This Supply generates DC high voltage 40kV, with which you can make interesting experiments.
When approaching the grounded terminal to the output of high voltage to about 4-5 cm you can see corona at wire ends
and when you put the wire even a little more closer, you can observe an electric arc.
Experiment 1: Get you hand close to the electrode (about 10-7 cm). You can feel electric wind blowing.
Touch the output. Will feel weak static pulses.
(It's not much worse than when you touch the sweater.) When the second hand grasps eg floors, will
again feel the static. Different light objects (paper, fabric, different packaging, plastic, but
even a plastic ruler) can be sticked to the wall or bottom of the table by the electrostatic forces. Some
objects stick to hand. Human hair can stand up slightly, but not
too noticeable (for that, Van de Graaf generator with a voltage of hundreds of kV is better).
Perform only if you stand on the non-conductive floor
and from all electrical appliances you have at least 0.5 meters away! Negative pole of circuit contact
to the ground.
Experiment 2: Pu two squares of aluminum foil about the size of 10x10 cm on the floor, one connect
to the supply output, the other do not. The gap between the squares leave about 5cm and into the gap put
wooden pencil. Perpendicular to the first pencil put another pencil. When you turn the high voltage ON, the pencil starts swinging.
(Attracted to the opposite charge and when it touches, and on the other side, as the charge equalises ...)
Circuit description: Oscillator with circuit 555 operates at a frequency of about
17 - 21kHz, it can be tuned potentiometers P1 and P2 for the maximum output voltage. Trimmer P1 affects
also duty cycle of oscillations. The output controlls the first transistor (PNP). Schottky diode
prevents its saturation and accelerates switching, but it is not absolutely necessary. The second transistor
is power NPN type. It must have a heatsink with area of least 200 cm2. Voltage is transformed
in the high-voltage transformer, which can be obtained from an old TV set (the transformer without built-in rectifier). HV AC voltage
is rectified and doubled in an circuit with external capacitor and two high voltage diodes. Diodes
are also from an television receiver (the anode of diodes can be identified because it is connected to the
output of high voltage transformer, cathode to the CRT). Capacitor can be made from plastic and aluminium or as a lyden bottle.
Thanks to the ultiplier you get the doubled output voltage 40kV. This high voltage supply is powered by DC voltage of 12-15V supply and draws around 3A.
