This is a little bug-zapper that works with a computer FAN and a CCFL inverter.
The insects will get sucked-in and then get zapped by a 2kV arc :D
It's powered by a 9V battery and is easy to use. The compact design also makes it mobile.
A video of the zapper in action:
Step 1: Requirements
• cutter knife
• hot glue
• computer FAN
• CCFL inverter (paper scanner or screen back-light)
• a 9V battery
• a 9V battery holder (clip)
• some wires
• a push-button
• some bare wire
• electrical tape
• high voltage diode (3kV+) or three times 1N4006 or 1N4007
• high voltage capacitor (500v +) (somewhere between 60nF and 10nF, NOT HIGHER!)
(using a bigger capacitor won't harm the circuit, but it would become lethal).
Step 2: The first cardboard piece
Cut the piece to the length of the CCFL inverter + 4cm (leave some room)
Now put the piece of cardboard around the computer FAN and cut it to length. Again, leave a few cm's over.
Edit: I actually advise to use PVC pipe here now because it's more fire resistant.
If you use PVC pipe, make sure the diameter is just large enough to fit on the FAN.
Step 3: Adding the CCFL inverter
Also add a bridge connection over the blue capacitor on the CCFL inverter circuit board.
You can do this by soldering a wire from one to the other pin.
Without this bridge, the HV capacitor won't charge.