This is an electric fly swatter, or racket zapper,
made for killing flies. But it also makes for a very cheap,
though limited, high voltage power supply.
Here it’s powering a Franklin’s bell. And if you just want to make some sparks,
it does that too. You can find them in stores like Walmart,
Home Depot, Maplin and many others,
for under $8.00 or 4 euros, and also online.
This one uses two AA batteries. It has a switch on the side
that you have to hold pressed for the high voltage. Here’s a closeup of the high voltage side.
It’s made up of three meshes. An outer mesh here,
a middle one with smaller holes, and another outer one on the other side.
Here I connect to the two outer ones. When I turn it on, there’s clearly no spark.
That’s because the two outer meshes are electrically connected together.
The high voltage exists only between the outer ones and the middle one.
To prove that I wrap some non-conductive tape around most
of the end of an alligator clip. That’s so that I can clip to the middle mesh
without electrically connecting the outer mesh.
The other wire is still connected to the other outer mesh.
Either one will do. This time I get sparks. And here I’ve set up a Franklin’s bell.
In the middle of the two cans is a ball of kitchen aluminum foil.
I couldn’t get it to work with a soda can top though.
It seems to need something rounder. But there wasn’t much else I could get working
with it. There wasn’t enough current to ionize enough
air for my ion wind rotor. And also not enough current for my big corona
motor. And I know it wouldn’t work with a lifter,
or a smoke precipitator, so I didn’t even try those. Here I’ve set up my oscilloscope
and Fluke 80K-40 high voltage probe for measuring the voltage.
You can see it’s relatively low, only around 1400 volts. And finally, time to open it up and see what’s
inside. I even pry apart the racket section
to see where the wires go to the three meshes. One outer mesh is connected to the circuit
via this yellow wire, the middle mesh is connected via this red
wire, and the other outer mesh is connected via
this other yellow wire. And looking more closely at the circuit board
we can confirm that the two outer meshes are electrically connected together,
right here where the two yellow wires go to the same place. I then unscrew the circuit board.
You can see where the positive of the batteries goes to the switch
and from there to the board. While the negative of the batteries goes directly
to the board. And for those really curious,
here’s the schematic I made from analysing it.
It’s almost the same circuit as this joule thief circuit I used
to power this compact fluorescent lightbulb. There’s just an LED and current limiting resistor
added to tell when it’s turned on.
And on the output there’s a diode to turn the output into DC,
and a capacitor for smoothing. There’s also a bleed resistor,
to get rid of the high voltage when it’s turned off.
Plus another resistor right here. But other than the LED and the modification
to the output they’re both the same blocking oscillator
circuit. And that’s the electric fly swatter, or zapper
racket. Well, thanks for watching! See my youtube channel, rimstarorg for more
neat videos like this. That includes one all about the Franklin’s
bell that I demonstrated. Another on making a much more powerful
30 kilovolt high voltage power supply. And one all about my compact fluorescent lightbulb
powered by the joule thief circuit. And don’t forget to subscribe if you like
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