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I am looking at designing a small bug zapper circuit of the type described in this post: How does this mosquito zapper circuit work?

Here is an approximate schematic of what I am trying to build: enter image description here

I have done some research into how this circuit works and also taken apart a mosquito zapper racket and tested the circuit firsthand. From this I've gain a basic understanding of how the circuit works via self oscillation and flyback.

What I'm confused about is how to correctly source the transformer component. I know I need one with 6 leads, but other than that I'm kind of in the dark. The transformer from the unit I took apart had no distinguishing markings so it wasn't much help.

Can anyone tell me what specifications I need in a transformer for this circuit to work?

Thanks!

Emmett Palaima
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    Cheapest source would be to buy a dollar store mosquito zapper. – Spehro Pefhany Jul 15 '20 at 03:12
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    @SpehroPefhany probably true, but I'd like to source my own part if possible. I'm trying to hack this circuit for an art project, have a lot of bug zappers firing rhythmically – Emmett Palaima Jul 15 '20 at 03:19
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    They're custom made for the product, if you specify the core size, ferrite material and all the winding and taping details, you can get a transformer maker to build exactly what your design requires. – Spehro Pefhany Jul 15 '20 at 03:21
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    @SpehroPefhany Okay, but I'd assume there are some generic options that would work as well. My question here is related to what specifications a transformer needs to work in this bug zapper circuit. – Emmett Palaima Jul 15 '20 at 03:55
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    @EmmettPalaima I'm not convinced that you sufficiently apprehend how the circuit works. If so, you would have written a relatively straight forward summary. I'm also not convinced that you are ready to design such a circuit. If so, you probably would have been able to provide us with a summary of the difficulties you anticipate and asked the question in a more informed and different way. Finally, because of your comment about rhythmically firing a lot of these without how you hope to achieve that nor details about what much be achieved, I'm worried this isn't the right tree to be barking up. – jonk Jul 15 '20 at 08:47
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    Killing a load of bugs for the sake of art is sadistic and cruel. – Andy aka Jul 15 '20 at 10:22
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    Leaving aside ethical considerations, there are many small transformers available from Ali*xpr*s* and similar sites (look for "high voltage transformer" and pick a small one). Just don't expect a specification or circuit diagram - you will have to do some investigation yourself. – user131342 Jul 15 '20 at 11:34
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    @Andyaka i'm not going to be killing any bugs lol. they're going to be set up to discharge harmlessly against a metal plate. it's just for the snapping sound and the visual spark – Emmett Palaima Jul 15 '20 at 19:57
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    @jonk I've tested turning one of these on and off with a darlington transistor in the place of SW1 (took apart a cheap dollar store racket to get the test circuit). It works fine, as the current draw on the 3.3V input is below 1A. As far as apprehending how the circuit works, that's why I asked this question. I understand in a broad sense that the circuit is causing a buildup of charge in the transformer that then jumps the dielectric gap between the two nodes once stored potential (voltage) becomes sufficiently large or an object (like a bug) completes a contact between the two nodes. – Emmett Palaima Jul 15 '20 at 20:05
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    @jonk The type of transformer specifications needed to achieve this behavior do not seem to be documented anywhere online, so I was hoping someone could help me understand this. The "sufficient apprehension" you say I am lacking is what I was hoping the answers to the post would help me achieve. If I already knew what kind of transformer specs I needed I wouldn't have made a post asking about it. – Emmett Palaima Jul 15 '20 at 20:11
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    @EmmettPalaima I'm a self-taught hobbyist, not a professional. So I really do get where you are at. I've been in similar places. And I kind of dislike myself for speaking like some disciplinarian. I'm not. Just the opposite really. But I also can tell you are more than one question away from where you need to be. Most especially because I don't think there is a ready made solution. I think you'll need to wind this yourself. And if you need to do that a lot, it's going to require some preparation and study. Parasitics are going to eat you alive. Both construction and design will be important. – jonk Jul 15 '20 at 21:40
  • @jonk Is there a reason I can't just find a workable component through standard electronics suppliers? There are 11,443 different transformer components listed on Mouser alone, it seems like it would just be a matter of searching out one with the right specs. Boosting a small DC voltage can't be such an esoteric application as to require a custom made component, can it? That really doesn't make any sense. – Emmett Palaima Jul 16 '20 at 03:23
  • @EmmettPalaima I can only claim my own ignorance. I haven't attempted to study 11,443 different transformer components. So I'm ignorant. But I do know some of what's needed to design and build one and I don't think any of those standard components are designed coincidentally for your very specific need. And swatter manufacturers will custom order something, anyway. So it is my ignorance. Nothing more or less. – jonk Jul 16 '20 at 03:32

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