About aphasic

May 2, 2016
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  • aphasic commented on Biotele's instructable MAKE A HIGH VOLTAGE SUPPLY IN 5 MINUTES4 months ago

    Wow, this Instructable has a lot of very low quality comments.Anyway, thanks to Biotele for the neat idea.I opened a 15W CFL and turned it on. It wasn't a problem to measure it with my AC voltmeter, which is rated for 300V. I measured the frequency, it was about 54kHz. I measured this with a Radio Shack digital voltmeter with a frequency function, using only one probe - the other was connected to nothing, but the readout was steady. I also noticed that when I connect one end of the AC voltmeter to one of the right two pins of the CFL bulb, and the hold the other in my hand (even without touching the probe metal), the needle goes way up - just from the capacitance in my body. I can touch both ends of the CFL bulb while it is powered, without a problem. It starts to burn my finger after a while but no heart attack. I tried first with two fingers on the same hand, just in case. When the bulb isn't fully connected, or is partially connected, then I get a shock, so be careful.The bulb was connected to four pins as in the pictures Biotele shared. I connected the outer pins to the transformer and got a 1/4" to 1/2" arc, but only after bringing the high voltage wires close together and drawing them slowly apart. The arc melted the ends of the wires a bit. Disconnecting the bulb from the pins, so that only the transformer was connected, did not seem to produce a stronger arc. The transformer primary effectively shorted out the bulb - i.e. the bulb did not light up when the transformer primary was connected across the outer pins. Moreover, the circuit was oscillating at 82kHz with the transformer in parallel like this, so I think the presence of the transformer affected the properties of the circuit. Also, one of the transistors in the CFL circuitry began to smoke.I tried connecting the transformer in series with the bulb. This worked using either of the outer pins. I could create an arc of about the same length as before, but this time the bulb stayed on - except when the arc got to its maximum length, and then the bulb started flickering and the arc made a buzzing sound.I didn't know very much about flyback transformers before this project. Apparently they are so named because they capture energy from the deflection coil in the horizontal "carriage return" movement of the electron beam between scan lines in a TV.I didn't look for a schematic, but followed the linked instructions for identifying the pins of my transformer (it came from a big HD color TV). It was interesting that there is a 20-30V drop when DC is applied to the high voltage secondary of the transformer, I guess this means that the rectifier consists of many diodes in series. I also could have identified the high voltage ground by process of elimination - it was the only pin on the base which was not connected to some other pin on the base. Selecting the primary was done by attaching to the various pins a 24 VAC, 1.25A power supply with a 22 ohm resistor in series, and looking for the biggest AC signal at the secondary (it wasn't very big).

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