Very sorry to bump such an old thread but I've been looking EVERYWHERE for information about the frequency emitted by the wings of insects in flight and how ultrasound disrupts them, and this was the only relevant thread that I could find!

Has anyone uncovered anything else about this bizzare phenomenon? Apparently it's a tried and trusted method of keeping flying pests away but I want to understand more about it before I invest in one.

Many thanks.

 

That was an old thread, indeed - http://forum.allaboutcircuits.com/showthread.php?t=6403&page=3

Welcome to the forums. Good luck finding your information.

 

Gee, that brings back memories.

An ultrasonic mosquito repeller project was my first attempt at making a PCB, many years ago. I didn't know what I was doing at the time, and changed the circuit. It used a piezo earphone as both the emitter and as the C in an oscillator circuit; and I tried sticking an amplifier stage in there - of course it didn't work.

A couple of years back, I bought a 3-pack of battery powered ultrasonic pest repellents from Harbor Freight (I think) for a few bucks. They seemed to work pretty well, and they were very inexpensive - but they don't seem to carry them anymore.

 

They actually worked? Wow, everyone else seems to deem them a big fat waste of money.

I'm still at a total loss of how these products supposedly work, I guess you could say I'm fascinated! The only plausible theory I've stumbled across is related to the mosquito - the ultrasonic repeller emits a 50 kiloHertz sound that fools mosquitos into thinking there's a bat around, which is a natural enemy of the mosquito.

So by this rationale, if the deviceis capable of repelling flies (which so many claim to do) then it would need to replicate the (non-existant) ultrasonic emissions of a spider? Or if it were to repel rodents then a cat?

I find the concept behind these products a tad inplausible!

 

These were briefly popular when I was a young 'un; about the same time as the fad for reducing travel sickness induced through static electricity by trailing a chain from the rear bumper of one's car. Both were a triumph of marketing over actual functionality.

IIRC, the ultrasonic mozzie repellers were supposed to work by imitating the male mosquito, and given that only the pregant female bites the bothersome ones shy away from males. Of course, that might all be made up (IR not an entomologist), the key is to make it sound plausible.

I bought one of those electronic water limescale inhibitors a couple of years back, and naturally the first thing I did was reverse-engineer it. Most of the circuit is concerned with flashing some lights on the front panel, but I fitted it regardless. Besides, there were strict, and plausible-sounding, instructions on winding the antenna wires in just the right way. I have noticed no appreciable softening of my water supply, and now I just feel slightly foolish.

 

I have a device here that will soften your water and repel ALL forms of unwanted pest. Mosquitoes, Rats, Mice, Daughters dates, salesmen, and milkmen.

$199.95 + $59.95 s/h.

It is built around the WORLD FAMOUS '555' chip. The LEDs blink to show its working.

Tech Support Call:

Us - "Thanks for calling 'All-Away'! How can I help you?"

You- "Um, I bought your all-away device, and It doesn't seem to be working!"

Us - "Ok sir, are the lights flashing on the front panel?"

You- "Yes. Yes they are."

Us - "Well Congratulations, sir! Your 'All-Away' is working at full power!"

You- "There still seems to be bugs and such around."

Us - "Oh. I see. You may have the RARE insects in your area that have nano-dna particles that make them immune to the 'All-Away'. What you need to do, is buy 2 more 'All-Away' devices and set them up so the signals intersect at 1.33 feet in front of the device at an angle of 30 degrees. This will confuse the nano-dna particles and keep them away. We take all forms of payment."

You- "I knew I HAD to be doing something wrong. Thank you. I should pick up a few more for friends and family!"

See, at All-Away, everyone ends up happy!

 

From what I read ultrasonics (or high frequencies in the 18Khz -22Khz) works better on teenagers than bugs. I suspect the cats and dogs will climb up your front and stand sideways on your chest figuratively saying "MAKE IT STOP! MAKE IT STOP!!".

A 555 works very well making these kinds of sounds. Done that, it was funny.

 

My government got rid of mosquitoes by putting anti-larvacide tablets in all the storm drains and ponds. Now most bats are also gone.

 

This is an old thread. In the circuit Ultrasonic Pest Repeller
http://www.electronic-circuits-diagrams.com/audioimages/6.gif
Can I use 555 ic as a low frequency square wave generator which is less expensive than CA3130 used in the circuit above. Is there any reason why CA3130 was used instead of 555 ic?

 

The very old circuit is missing an important supply bypass capacitor so adding another 555 oscillator will mess up the supply voltage without having a supply bypass capacitor (the 555 draws 400mA from the supply for a moment each time its output switches).

The circuit might scare away dogs but will not affect mosquitoes.