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Registered Member #2099
Joined: Wed Apr 29 2009, 12:22AM
Location: Los Altos, California
Posts: 1716
We have one of those high-voltage flyswatters. Not just a novelty toy, it's very effective against little brown pantry moths in the kitchen, without making moth-colored spots on walls or food containers.
While it was open to fix mechanical damage (somebody had dropped it), I took the opportunity to trace the circuit and make some electrical measurements.
The circuit is familiar from disposable-camera-flash and Joule Thief applications.
Short-circuit output current is about 2.3 mA, and open circuit voltage is about 1700 volts. I was reminded that my favorite analog multimeter has a higher input impedance than a standard DMM: 20 megohms on 1000 VDC range. But final measurement used a 40kV EHT probe with benchtop multimeter.
It's worth noting that the HV capacitor has a nameplate rating of only 250 VAC. But in addition to many national safety-agency seals, it's labeled as an X2-class capacitor. Class X capacitors are very conservatively designed for permanent connection across the mains, with minimal risk of fire or explosion if they fail. "Class X2 capacitors are intended to operate safely even in the presence of spikes on the mains supply of up to 2.5 kV" according to
Registered Member #72
Joined: Thu Feb 09 2006, 08:29AM
Location: UK St. Albans
Posts: 1659
The output on those things is so low that it can be difficult to tell whether the wasp has been hit or not. I've been thinking of replacing the circuitry to give perhaps 5kV, backed up by 2uF, (supply in a "ghostbusters" belt, wouldn't fit the handle) then you'd be able to tell when it hit. The problem would be that my wife then wouldn't let me use it with anybody else in the room.
Registered Member #191
Joined: Fri Feb 17 2006, 02:01AM
Location: Esbjerg Denmark
Posts: 720
I've read somewhere that some guy upgraded the circuit for wasps. He mentioned something about needing a higher voltage(kVs) to punch thru the exoskeleton, and a lower voltage capacitor(hundreds of Vs) to provide the energy.
Registered Member #1408
Joined: Fri Mar 21 2008, 03:49PM
Location: Oracle, AZ
Posts: 679
Where did you buy it? I'd like to get one also. The schematic looks right but I id a breadboard and I didn't have a transformer that worked. I tried a very small OLDfashioned flyback but it didn't spark even with 15v 3A I used a MJE13009 transistor and a variety of caps - no go.
Registered Member #2376
Joined: Mon Sept 21 2009, 05:13AM
Location: Brisbane, Australia
Posts: 14
Being in the sub-tropics one these would come in handy indeed!
The transformer at least bears quite a resemblance to those found in those 12V fluoro ballasts used to power a little 8W tube for a mechanics lead light... I wonder...
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HV flyswatter and safety-rated capacitors
