Mosquito Zapper - Different approaches, and circuit diagrams...

Hello,

I'm in the process of designing a mosquito zapper. I tried to gather as much details as I can about their theory of operation and popular circuits. I have also a bunch of them here and I have already opened some to take a look at their inner workings. Well, as an embedded designer, I do not get involved a lot in analog circuitry. However, I believe mixing the two distinct domains one can come up with a much better and improved design over what's offered out there.

From what I noticed so far, some of the cheaper designs had their circuits built around HV caps, diodes, etc. No transformers or ballasts used. A bigger device has more powerful circuitry, transformer-based design, and a ballast for the CFL.

Now the question is; what are the best practices available today to design such a device? What is the advantage of the transformer-based design over the other one? Is there any way to achieve same results (output power for the arc) without the transformer? How about miniature transformers?

If you can share some circuits, it would help a lot!

Thank you!

Really cheap Chinese made ones use simple voltage multipliers using a chain of diodes and capacitors. The CFL is a normal inductive ballast. Although there is some voltage in each stage of a voltage multiplier, driven from mains AC they can still produce several KV with only a few low cost components.

Brian.

Hello Brian,

Thank you. Well, this is one of them I got off the web:



[Found at electronicsforu. com/ wp-contents/ uploads/ 2016/ 05/ EC5_1. jpg]

It's a cheap one built with simple discrete components. However, the output arc of such a circuit doesn't fry all mosquito and some of them escape the mesh after getting shocked. What do you suggest to increase the output voltage, adding more stages to the ladder or replace caps with higher rating ones? If I can achieve better results without the transformer, I would prefer to go that route.

Thanks

By the way, it would be great if you can elaborate more on the CFL circuit and how to make it power different CFL, say 18W, 24W, or smaller ones like 4W.

You can increase the voltage by simply extending the diode/capacitor chain. For example adding a duplicate of C5,C6, D5, D6 to the end of the existing ones. It doesn't give you something for nothing because the voltage isn't exactly doubled and the current that can flow is also reduced but I doubt a mosquito would care much about that!

For the CFL, the biggest improvement would be to change from a white to UV tube. It wouldn't look much brighter to our eyes but insects can see further into the UV spectrum where the light seems brighter to them. If you really want to increase the tube power, the most satisfactory solution is to use a choke and starter as in domestic fluorescent fittings or a an electronic starter for normal lamps. You can try changing the value of C7 but it isn't a very predictable way to do it. Increasing the value will cater for more powerful lamps. you probably don't want to change D7 or R6 as these make a crude starter circuit which should work for almost all lamp ratings.
The value of C7 decides it's reactance '1/(2 * pi * f * C)' which roughly equates to the value of an equivalent resistor doing the same job. 'f' is in Hz and is your AC line frequency, C is in Farads and the result is in Ohms.

Brian.

Thank you Brian!

By the way, the schematic says the caps C1~C6 are 630 VAC. That means it is rated @ 1 kVDC. Do you think this value is correct?

AC and DC ratings are not quite the same thing but for low frequencies if you multiply the AC rating by 1.414 (square root of 2) it will give a minimum DC rating that should be safe. So 1KV rating should be fine. Increasing the voltage rating just gives a wider safety margin, it doesn't make the voltage itself any higher.

Brian.

I think 630VAC is a typo. Each capacitor gets charged to slightly more than 300V DC , so 630V DC which is a common easy to find rating already has an adequate margin.

I've taken apart several Wal-Mart bug zappers and they
all had just an inductor (ballast) and the horseshoe UV
tube, and that's it.

The UV tube is always what goes out. Might suggest
you split the problem into two parts, attraction and
punishment. UV LEDs up through UV-C can be had.
Whether any UV source really does the job is a real
question. I live in a very "buggy" locale and get a lot
of "by-catch" but the mosquitoes seem to mostly
hover around, but not encounter, the grid. Many
commercial zappers add an expendable attractant
now (octenol?).

You can make a deadly voltage and then some with
any sort of chopper switch and a car ignition coil.
I would keep the chop rate down and the "on" pulse
width narrow if you want battery powered. The dwell
time doesn't need to be huge to get kV out. I'd put
a HV rectifier at the coil output and let the grid
self-capacitance hold the voltage up. A mosquito
doesn't take much charge / current to kill.

If you free yourself from 50/60Hz power then you
could make a solar powered zapper that works when
it needs to (sunset to just after) and can be located
such that it draws bugs away from, rather than
toward, the house. Just need enough battery to
work for the couple of hours of "prime time" - cast
off NiCd / NiMH might do for this, they are more
tolerant of "dumb charging" (so are gel lead acid)
at C/10 - charge the batteries all day and then "live
within your means" for a few hours until run down.