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Old 10th December 2011, 12:55 PM   #1
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Default Centre tapp transformer

I am building a cercuit to produce a high power 20MHz sound to stop a neighbours dog barking. I have tried a commercially available device and it is useless. I need to build a transformer with the following characteristics:

Primary 150 turns 28 SWG
Centre Tapped
Secondary 40 turns 24 SWG
Core ferrite U type.

My question is where can I find a suitable core and does anyone have instructions of actually how to build it. Any advice on how to increase the power outpt appreciated.

According to the circuit diagram I have the output needs to be connected to a 5W tweeter.

Many thanks for any advice, the dog is driving us mad !!!
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Old 11th December 2011, 07:52 AM   #2
Mooly is offline Mooly  United Kingdom
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I don't think a tweeter has much response at 20Mhz

Why do you need a coil/transformer to drive a 5 watt device ?
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Old 11th December 2011, 03:19 PM   #3
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Location: Lakewood, Ohio
I'm sure that the the "20Mhz" was a typo and he meant kilo.
But I also think that Chris is in over his head and there are other easier ways of building this type of unit.
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Old 12th December 2011, 01:46 AM   #4
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Hi Guys, thanks for the replies. Yes it is KHz

I will see if I can post the circuit diagram.
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File Type: jpg circuit diagram.jpg (279.6 KB, 32 views)
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Old 12th December 2011, 08:57 AM   #5
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Who designed that circuit? It would be easier and cheaper to do a complementary/mock complementary - hey, you don't care about the distortion, use a switching circuit, drive square waves into it, and assume the harmonics are not going to be reproduced by the driver. A five watt amplifier is not that difficult (finding a tweeter that can take five watts of 20k continuously might not be as easy as it seems), although you might have to bridge it to get the power into a medium impedance tweeter from twelve volts. Still cheaper than building the output transformer; that's tube mentality.

But, in my experience, dogs start to bark when they hear high frequencies, not stop. If you had a bark detector circuit, which applied an aversion shriek every time it heard the dog, I could understand the philosophy, but as it is, just "turn it on and make the beast unhappy", I don't see how it can learn that it's its own actions that are triggering the discomfort.

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Old 12th December 2011, 09:17 AM   #6
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The circuit was from a web site but I can't remember where. It is not on continuously but will be linked to a detector and relay (like a clap detector) so the circuit will only emit a high frequency in response to the barking. The idea is that the frequency is not liked by the dog so the dog is conditioned - provided it is not deaf of course. Sorry for not making it clear.
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Old 12th December 2011, 10:19 AM   #7
Mooly is offline Mooly  United Kingdom
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