Fly Killer

[mirel]

My father needs a fly killer for his meat store in the market. It must be for 12V. I took one of 220V and changed the 4oooV transformer with my circuit. I also changed the UV lamp to UV LED. The transformer is from the spark in our old car and the diode is from old TV. I can get only 2000V but I need 4000V. Can you help?

 

[alec_t]

My guess is the pulse rate is too high to allow the inductor current to ramp up to a sufficient value. You could try increasing the resistor value (e.g. double it) to reduce the pulse rate and hence prolong the ramp. However, increased inductor current would also mean a higher back-emf spike when the FET switches off. Your FET is rated for only 200V. Ignition coil spikes are typically higher than that, from what I read.
Do you know the coil's primary inductance? Do you know the diode's voltage rating?

 

[audioguru]

I agree that the fairly low voltage rating of the Mosfet is clamping the voltage spike.

 

[moty22]

Put a little shower in front of the HT wires, wet fly will die from 2000V only.

 

[cowboybob]

Put a little shower in front of the HT wires, wet fly will die from 2000V only.

Probably impractical, but I DO like your thinking .

 

[audioguru]

2kV will probably kill me, why won't it kill a little fly?

 

[moty22]

Thank you guys for supporting and the liking my "practical solution".
Another solution: from experience I know that the ignition transformer have a turns ratio of about 1:30 , it means that the high voltage can come from back emf only. I also know from experience that the mosfet will explode the first time the voltage will go over 200V.
My suggestion is to revers the diode. The reason is that we can't tell the direction of the winding and it could be that the negative spike caused by back emf is higher in amplitude.
If that doesn't work then it likely to be what alec_t said.

 

[debe]

Use a TIP152 transistor to drive the IGN coil, they are an ign switching transistor ive been using. You should get around 20KV from an ign coil. TIP152 transistors are quite cheap from China on Ebay. I purchased 10 from China on Ebay & they work fine in IGN circuits, they were marked as made in the Philipines.

 

[audioguru]

Why does the fly killer use a diode to make DC? A car ignition circuit does not use a diode so the polarity of the high voltage does not matter.

 

[debe]

This is a typical mains Bug Zapper & its bascicly a HV AC transformer.

 

[debe]

This one is an inverter type using a tripler type circuit for the HV. This is one of those racket type bug zappers.

 

[gary350]

I use a funnel and quart mason jar to catch flies. Drill a hole in the lid then solder or glue a funnel to the hole. The funnel spout needs to go down about 2" down into the jar. Put 3 day old small piece of meat in the bottom of the jar then screw on the lid. Flies walk down the funnel to the inside of the jar then can not get out. It is amazing how many flies this will catch. One time I took about 10,000. flies to work and turned them loose in the bosses office. It looked like a gray smoke cloud in his office. LOL. Everyone joked him all day about how he attracts flies. I gave a friend a box of flies for his birthday gift. LOL. I use to have fun leaving a lunch bag full of flies in the work lunch room, thieves use to steal the lunch bags. Use to put other things in the lunch bag, 2 week old french fries, dehydrated hamberger, aluminum foil wrapped dog poop. LOL. You can have a lot of fun with a large bag full of flies.

If you put a jar full of flies in the refrigerator after 30 minutes the flies can not move. You can pour them into other containers. 30 quart jars of flies are a lot of flies.

 

[mirel]

Hello.
You gave me many good ideas to try, thank you.
I tried what alec_t said. When the 555 output is high for 80% the HT is 3.5KV.
I tried reverse the diode and the HT now is -4.5KV. Now I can kill dry flies too.
My father likes very much the idea of the jar and the funnel, he wants to try it. He think it must be true because he has 3 days old meat in his store and in the summer he has more than 10000 flies.
Maybe I will try to put shower like your joker, moty22, say.
Maybe I will try TIP152 if I can buy it.
I have multimeter and no oscilloscope. When I put diode and capacitor on the HT I can measure it with a probe I made. It is voltage divider by 10 from 10 resistors of 1Mohm.
My friend in Caen have oscilloscope. I think one day I will exchange his oscilloscope for a bottle of vodka. I will give him the vodka and when he is drunk I will run away with his oscilloscope.

 

[dr pepper]

You can buy bug killers that look like a tennis racket really cheap, I got a couple from the pound store, there is a circuit inside that generates 6kv from batteries, a bit of a heatsink on the trans would make it run for longer periods.

I used a 20n60s5 mosfet to pulse a ignition coil as part of a hf start for a tig welder, it seems to be reliable enough.

Sorry debe, I just realised you allready mentioned tennis racket type bug killers, I didnt mean to steal your thunder.

 

[kinarfi]

If you look at the circuit for those tennis racket bug swatters, there is a bleed down resistor for the capacitor that feeds the grid, remove it, makes it work a lot better, but it does hold it's charge for quite a while,

 

[dr pepper]

I spotted that on the couple I have, I spose they dont want you zapping yourself.

 

[audioguru]

I guess they use DC so that a capacitor can slowly be charged by the very weak electronic circuit then it can deliver plenty of current to zap a fly.

 

[debe]

You are quite right audioguru, only mine doesn't have the bleed resistor. I modified one to use as a gas lighter. As long as the button is held down there is a continous arc.

 

[flat5]

Some cheap high voltage modules here.
https://www.banggood.com/buy/High-voltage.html
I have used
https://www.banggood.com/DC-3_6V-6V...r-Module-High-Voltage-Generator-p-915426.html

Using 2 AAA cells It can arc >8mm.

 

[audioguru]

Can anybody understand the broken Engrish from the Banggood ad? When they make an English ad then why don't they hire an English-speaking electronics-educated person to do it??

I saw a tennis racket fly swatter high voltage zapper at a new huge ultra-cheapo store. It was selling for $3.00. I didn't buy it but I bought a multi-color multi action LED module with three button battery cells instead for $1.25. The controlling IC and three LED chips are inside the 5mm LED. It is very bright.
I was thinking of all the expenses and profit of the manufacturer, importer and store. Then the stuff must be made VERY cheaply.