challenging problem - mosquito kill counter

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pluukkanen

New Member
Hi. I've got this weird project of mine of making a counter to one of these electric racquet-type mosquito swatters. I know it's sort of macabre, but we've got SO many of them around here that it'd actually be fun to know how many have become roast during the summer.

Sanity issues aside I know that they're not toys and do produce a nasty voltage of 1500 V at the business end of the racqeut. Kills a mosquito and gives a sort of a nasty pinch if you touch it yourself.

I'm currently contenplating how to make a safe notion of a "kill". My idea is that if you could measure the increased current drain / drop of voltage from the 2 x 1.5 V volt battery set and somehow convey this to picaxe input. Rest of the electronics would be basic picaxe interfacing which I'm familiar with, but I'm really short of ideas how best to convey the kill data to picaxe. Would it be possible to make a circuit that would notice if there's ANY current drain from the 2x 1.5 v battery set as in resting mode (when there's nothing frying on the grid) it shouldn't consume any electricity.

Any ideas would be appreciated!

Thanks!
 
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demonicpicaxeguy

Senior Member
some of the timers in these pic's can act as a rising edge or falling edge counter, hopefully the voltage drops enough to cross the threshold

the only concern is that when it Zaps somthing there could be a small zap back into the batteries/picaxe, so it might pay to have a diode in there as well
 
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hippy

hippy

Ex-Staff (retired)
I think one would need to know what the circuit of the mosquito zapper is to work out the best way of determining a 'zap', although any glitch or pulse in the system could be amplified enough to be detectable and countable by a PICAXE - I recall a post sometime ago about reading tacho information off a vehicle +12V power line that way.

It's really a case of finding the best place to add glitch detection. With kilovolts around you'll likely want to keep that well away / isolated from the PICAXE and whatever else it's connected to.
 
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Andrew Cowan

Senior Member
How are you going to make the 1500V volts?

I guess the ones you buy use a oscillator and a Cockcroft-Walton generator. These do draw a current (as does the oscillator), even when no fly is present.

Andrew
 
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Dippy

Moderator
Andrew, he's already got the swatter and wants to know how to make a circuit to detect the zap.

Cockroft-Walton? I think someone's been Googling :)

I would imagine the design will be the cheapest design multiplier in existence.
 
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pluukkanen

New Member
OK. Here we go. Here's the inner workings of one of the zappers. As I undersand - from right to left - there's a power led, a transistor, two resistors, converting? 3 V DC to AC for the transformer, after which two diodes to to convert it back to DC and a few smoothing capacitors.

I suppose anything going to Picaxe would have to be taken before the transformer and it should also be a sort of safe to do so. There should be nothing coming back through the transformer, right?

Would it be possible to just split the wire going from the battery to a picaxe analog input and detect the minuscule drops in voltage a) when the key is pressed and the LED comes on b) when the bug is being cooked.

It'd be kind of a handy as well since I wouldn't have to deal with the zapper circuitry at all. Might have to use a different power source for the picaxe though.
 

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hippy

hippy

Ex-Staff (retired)
Presumably the transistor makes for some sort of oscillator, through the transformer then a voltage multiplier and that's the 'dead bug' end sorted.

Without knowing what the current flow and voltage levels are it's going to be hard to say what distinguishes between normal running and a kill. Does a kill even affect the oscillator and battery side ? I'd put a scope or meter across the batteries and see if there is any change as you feed bugs into the afterlife.

With an oscillator and high voltage, monitoring current or voltage anywhere else could be hard. It's an interesting challenge which I don't have any good ideas for.
 
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leftyretro

New Member
You might be able to build a 'wireless connection' to the zapper. I'm sure it puts out a health EMI pulse when it does it's kill and a simple diode detector placed near the unit should be able to generate a small DC pulse on activation. This could possibly, with proper signal conditing, generate a interrupt pulse to the picaxe and increment a counter variable. Displaying the kill count and being able to reset the counter would also have to be designed but that's easy stuff.

Lefty
 
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pluukkanen

New Member
indeed the led does blink a little and the whining noise (no idea where it comes from) that the racquet makes becomes sort of intermittent when the bug is being coooked. i have to check the voltages when i get my hands on a multimeter. It's funny that no one has thought about this kind of a "zapper on steroids" before . I shouldn't be the only odd one out there...
 
hippy

hippy

Ex-Staff (retired)
It's funny that no one has thought about this kind of a "zapper on steroids" before

I suspect few have ever worried exactly how many are being killed, just happy that they are :)
 
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Andrew Cowan

Senior Member
pluukkanen said:
indeed the led does blink a little and the whining noise (no idea where it comes from) that the racquet makes becomes sort of intermittent when the bug is being coooked. i have to check the voltages when i get my hands on a multimeter. It's funny that no one has thought about this kind of a "zapper on steroids" before . I shouldn't be the only odd one out there...
Click to expand...
The whining noise is coming from the oscillator - the pitch of the whine is the frequency of the AC being created.

It sounds like the caps are being charged with a high voltage, low current charge.

As the caps fill up, their resistance increases, so the current decreases until it stops when the caps are full. (However, current on the other side of the transformer may continue.

When you kill a fly, the caps are somewhat discharged, so again current is drawn - you should be able to sense this.

The LED 'blinking a little' is the caps discharging, then recharging.

Andrew
 
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Rickharris

Senior Member
Put a button on the handle to clock a counter up when you hit one. I can't imagine you will be able to find anything measurable in the horrible C$"p the oscillator circuit throws out.
 
hippy

hippy

Ex-Staff (retired)
Replace / parallel the LED with an opto-isolator and that could be a useful switch. Not sure what nosie / EMF problems you'd have though. Probably best to run the entire PICAXE off it's own entirely isolated supply.
 
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Brietech

Senior Member
You could try putting a little loop/antenna of some sort, along with an opamp, and just put it really close to the zapper. If you have a scope lying around, I bet it throws off a decent bit of EMP noise when it discharges =)
 
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manuka

Senior Member
Buzzing death angel mosquitoes are no ones friend, & annually kill millions of humans & animals with malaria & West Nile etc. Tales abound of fresh breeding grounds in abandoned swimming pools once the playground of the US suburbs...

Sorry to spoil the PICAXE fun, but it transpires black-light "bug zapper" type traps are not suited for mosquito control. Some decades back, when based in a sub tropical Pacific mozzie playground,I used an industrial strength version of such a zapper. Yes- it certainly worked, although noise & cooked insects aromas often would keep us awake! But overall it was probably better to consider a "body count" in the morning, as my attempts to monitor the mozzie zap rate revealed several flaws-

1. NUMEROUS other insects were also attracted- especially moths
2. Not all zaps kill the insects- some are just tickled & come back for "repeat treatment".
3. Insects when killed may remain on the grid & receive multiple zaps before cooking/carbonizing & smoking away/falling free.

The night time use these zappers is considered dubious anyway. A frequently cited study, Frick, T. B. and D. W. Tallamy. 1996. Density and diversity of non-target insects killed by suburban electric insect traps. Entomological News. 107(2): 77-82, found that black-light traps do a poor job of attracting the bloodsucking female mosquitoes & other biting no-see-ems, & may attract and kill many more beneficial insect species. Yes- some night fliers actually are our pollination pals! The zapper traps were therefore considered to be environmentally harmful because of damage to the natural fauna. Their best use is day time indoor house fly zapping it transpires- much as often seen in food shops.

Propane-fueled carbon dioxide traps, or even dry ice in a bucket, may be far superior for mozzies, which are very CO2 attracted. See the likes of =>http://www.mosquitokillingsystem.com/ & even the sweet tooth approach =>http://news.bbc.co.uk/2/hi/health/5370110.stm. These are far more selective and don't tempt/harm beneficial species.

In fact a pedestal mount electric fan providing a "blow em away" breeze can be most effective.Try it!
 
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moxhamj

New Member
I'll second those comments, manuka.

But darn this mosquito thread. I'm starting to hear mozzies where I know there are none!

Another way to get rid of mozzies. Don't let your 12 year old son dig a big hole near the house which then fills up with water.

In fact, when my grandma was growing up in Brisbane, it was an offence to have anything in the garden that might collect water that mosquitos could breed in.

I've broken their breeding cycle in summer simply by not watering the garden for a week.

I also like the fan idea. It blows away the C02 and also means the mozzie is like a fighter plane trying to land on an aircraft carrier in the dark.
 
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boriz

Senior Member
The whine is generated by an inverter, the same whine you get from a camera flash. If you measure the current drawn by the circuit it will be highest immediately after a zap. This could easily be 1 or 2 Amps. Within a few seconds the HT side will be fully charged and the load on the battery will have dropped considerably, perhaps to just a few tens of milliamps.

The high current ‘recharge’ part of the cycle can easily be detected with a current shunt, or even a hall-effect device. It will also be accompanied by a brief drop in the terminal voltage of the battery as the current pulse drops across the internal resistance of the battery. I would not be surprised if this drop is several tenths of a volt. More than enough for a PICAXE ADC to detect. The PICAXE should be powered from a separate battery with a higher voltage, 4.5v or 6v through a diode. Then connect the grounds and simply connect the swatters +ve battery terminal to the PICAXE ADC.

You will probably need to take extra precautions to protect the PICAXE from spikes on the power lines and RF pulses.
 
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Dippy

Moderator
Blimey Stan, he's only on about one of those electric fly swatters. Let's not go OTT and spend too much time Googling :)

Therefore he can be selective about what he kills. If it makes a zzzzzssssszztt noise it gets slapped. Frick and Tallamy (who really ought to get out more) needn't be worried.

And after the amount of times I got bitten during an evening tennis match the other night then you can annihilate the whole family as far as I'm concerned. I'm going to make a 3MegaVolt 20 square metre version.

Typical females, if they're not after your blood then they're after your wallet ;)
(Just kidding ladies).
 
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manuka

Senior Member
Dippy-fair comment. However this field was (part of) my educational day job ~10 years back,c/w significant academic footwork, & my awareness of mozzie publications is relevant.
 
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Rickharris

Senior Member
It is well documented that black light does a poor job of attracting mozzies but attracts many benificial insects - to their death)

The BBQ type of black light killer also spreads body parts far and wide so beware of eating your BBQ under one or you might get more on your plate than you think.

Swat, spray if you can stand the smell, I favour a listening post to home in on the blighter and highlight their position with a laser spot - Killing them is not problem - Finding them in the bed room is even if you can hear them.
 
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pluukkanen

New Member
Actually what came to my mind was that it'd be fun to install one of those cheap 5 mW red lasers to the front part of the racquet handle and with a spinner mirror create a very thin cone of laser light, say 30 degrees or so. This would make it very easy to spot the bug in pitch black room as it would leave a marked shadow when you'd hit the bug with the laser. Certainly just as sane as making the counter, but oh, so cool...
 
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Dippy

Moderator
You've met a few in the literal sense?

Do you mean you met them at a Book Convention? Did any of them have a nice soft back? Or were they left 'on the shelf'?

Actually I'll attach a 5mW laser to my tennis raquet just to distract the opposition - I need all the help I can get. (Don't do this at home kids).

I think if I get to the stage of running round pitch black rooms with a raquet and spinning lasers then it'll be time to put me in a Nursing Home! (Oh, there's the white van now.)

Nothing wrong with eating insects Rick. Some Johnnies have been doing it for years.
 
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Dippy

Moderator
I think that may affect the balance of my tennis stick a bit.
I'm sure I can find a picture of a bigger one.
 
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pluukkanen

New Member
www.wickedlasers.com sells green lasers up to 300mW which should be hefty enough to drop a mosquito if it can light a match or pop a balloon. It just gets too complicated to build a guidance system around the laser which would automatically locate the bug and fry it on the wall or in the air. I don't think picaxe wold be up to the job either?

Not to mention that a 300mW will set you off 2000$ and be sort of hard to import as well. Legal limit around here is 5 mW, thus the modest choice of power. And there's the sanity issue as well... .)
 
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Dippy

Moderator
"And there's the sanity issue as well... .)"
- I'm glad you said that :)

Mind you, if you get it to track the Mother-In-Law's earlobes that would be fun.
 
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Michael 2727

Senior Member
Use an optocoupler or Photo Cell as Hippy said to detect
when the indicator LED goes LOW, allow a 5 Sec Delay
for the sukker to get well fried (blah at undercooked critters)
Then in the morning do a head count and compare it to
the Picaxe count.
Picaxe + 1 component + counter (optional) doesn't get much simpler.
 
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Andrew Cowan

Senior Member
If we are talking about effective ways to kill mosquitos, what about some kind of explosive? Destroy a 20 mile diameter circle, and you'll kill any mosquito near you. Problem solved once and for all!
 
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moxhamj

New Member
Sounds like some grafitti I once saw on a bus stop when I was growing up: "Go Ronnie, nuke em till they glow!"
 
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