to make a ultrasound speaker

[walid ahmed]

How to make an ultrasound speaker that'll produce above 20khz frequiency to repell mosquitos???????any great idea

 

[davenn]

How to make an ultrasound speaker that'll produce above 20khz frequiency to repell mosquitos???????any great idea

you need an oscillator at the required frequency and an ultra sonic speaker
these are readily available online ... do some googling and ebay searching

 

[shrtrnd]

I used to make them when I lived in places where mosquitos lived.
There are a lot of simple circuits free on-line.
The critical part is a piezo speaker, that's the only way you get to the high frequency needed.

 

[unclestan]

Interesting. I need to look at ebay for that piezo speaker.

 

[hevans1944]

You should look at this Google result first. You may be able to build your own "ion tweeter" or "plasma tweeter" that could be more effective than a piezoelectric transducer. If you can do that, throwing together an ultrasonic oscillator/amplifier is a "piece of cake" as us electronic project bakers put it.

You might also want to consider other routes to mosquito control: infrared source to attract 'em, small fan to "suck 'em in" and an electric zapper to finish them off. Here in Florida, the county periodically uses foggers, spewing forth lethal chemicals, in an effort to control the mosquito population. Not sure how well that works, so it's a good idea to rub on some DEET before venturing out in the evening.

 

[kellys_eye]

Here on the West Coast of Scotland we have plagues of 'midges' (noseeums to many) and use dedicated machinery based on scent production, CO2 emission (yay!), warmth and a vacuum device to suck the bleeders out of the air.

Basically it's a mechanical cow......

Place is (in)famous for them:

http://www.dailymail.co.uk/news/article-4779094/Walker-trapped-tent-midge-attack-Scotland.html

 

[Audioguru]

Many piezo tweeters "claim" to produce frequencies to 27kHz but they lie about it. They fall off above 18kHz.
Here is a typical piezo tweeter:

Look at "Does an ultrasonic repeller repel mosquitos?" in Google and many answers are NO.
Mosquito zappers were sold with a propane flame making CO2 that mosquitoes think comes from the breath of a mammal. Then the attracted mosquitoes are zapped with a high voltage. Now my city puts lavacide in ponds and drains (it is safe for birds and animals) so most of the mosquitoes are gone and also the bats that used to eat them.

 

[shrtrnd]

Audoguru has a point. If you go with a peizo speaker, a lot of manufacturers don't live-up to the specs they claim.
There are some other good ideas in this thread that I haven't heard before.
When I selected the peizo speakers I used way back when, I made sure I got ones that were good at 20Khz.
My application was for use in a confined, enclosed patio. I didn't think what I built would work in an outdoor application. Some of the other ideas I've read here might be better for you if you intend an outdoor application.

 

[Audioguru]

A proper specification of frequency response says how much the output level deviates from being flat. +/- 3dB is audible but the cheap piezo tweeter specifies 4kHz to 27kHz without saying how much deviation. Maybe it has a huge notch of -30dB at 22kHz? Maybe 27kHz is at -60dB?