ultrasonic mosquitoes repeller

[BPNGUYEN]

Hello every one;
I would like to build a mosquitoes repeller. I did some researchs and come up with two promising circuits. One is use NE555 OpAm and can use 9 to 12V battery. The second circuit is use a phase locked loop (CMOS4047) wired as a 22kHZ osillator. The output is amplified by a pair of NPN transitors and drive a Motorola 3.25 inch Piezo. Current drain of this circuit is about 120mA and has to use an external power supply which is I don't realy like to do. > Do you have any recommend about this? Do you know at what frequency the mosquitoes hate the most? ???
Best regards
Ben Nguyen

 

[GPG1]

LM/NE555 is not an opamp, CD4047 is not a phase locked loop.
A 555 will drive the piezo directly. Use a CMOS vesion for lowest current draw. There is no evidence that these devices actually repel mossies.

 

[audioguru2]

Hi Ben,
Welcome to our forum.
The ultrasonic sound from the piezo tweeter might actually attract mosquitoes, if they can hear that high, because they might think it is a nice warm bat that is making the sound. But they probably know what bats do with mosquitoes (their dinner), so will be repelled. Who knows? Try it and see.
If the circuit doesn't draw much current, then its output power will be low and it won't have much range. A piezo tweeter is a small capacitor and needs a high voltage swing to provide any power output. A 4047 by itself with its outputs used as a bridge will produce twice the voltage swing of a 555, and still operate fom a 9V or 12V battery.
Attach or link to the circuits that you've found and we'll check them out for you.

 

[darrins]

I don't know that these ultrasonic devices are effective at repelling mosquitoes. An alternative that I've heard about uses low frequency sound to ATTRACT mosquitoes. The theory is that the low frequency sound mimics a heartbeat.

http://www.sonicweb.com/

 

[audioguru2]

Hey Darrin,
Instead of buying that expensive gadget that makes heartbeat sounds that they say are, "inaudible to humans", why not just loop the beginning of Pink Floyde's, The Dark Side of The Moon rock song?
Feed the 16Hz heartbeat into a high-power amp and a big subwoofer. Then if you don't hear it, you'll surely feel it. ;D

 

[darrins]

audioguru,

Sounds good to me. If it doesn't work on the mossies, you can crank it up and scare the hell out of the neighbors, especially that part right after the heartbeat ends. 8)

Darrin

 

[audioguru2]

Yeah man, that's cool.

 

[trigger]

I have disassembled a cheap mosquitos repeller. it just use 2 transistors, a few R and C, and a piezo buzzer....

May be later, I trace and draw the circuit out....

 

[audioguru2]

Hi Trigger,
Welcome to our forum.
You've found a product with a very simple circuit.
Before you took it apart, did it actually repel mosquitoes?

 

[trigger]

........... ah......... who knows...... just it comes with a pack of batteries as an add-on gift

but I will try check its output frequency

 

[trigger]

Here is the draft circuit diagram of the repeller I have.
Hmm.... it just buzz.... and I heard the sound.......
I can't guarantee it works on repel mosquitoes...... it is just for fun only..... and I haven't rebuild one myself......

The NPN transistors are SMT components which marked L6, I haven't check its part number but I believe it is from On's Semi.

The coupling capacitor C is 1000pF where I haven't put its value in the schematic...

And the switch is for select high or low buzzing frequency....

So if any of you have build it and test with a mosquitoe, then let us all know about its performance.

8)

View attachment 35788

 

[surajbarkale]

I tried about the same transistorised circuit a few years ago. It worked successfully for a day or two & then mosquetos got used to it . What the hell i tweaked the RC values to change the frequency (by how much i don't know ) but no avail. Hope it works for you. ;D

 

[Dido]

Here Is the circuit I`ve been using for one year.The mosquetos can`t got used to is because I`t changes It`s frequency all the time so the mosquetos can`t get used to it It`s efficiency is better in dark areas.

for the beeper you can use beeper 400ST - a 40Khz working frequency

for the repellant

D1D4 - 1N4001.
R1 - 3.3 М, R2 - 680 к, R3 - 10 к, R4 - 3 к, R5 - 4.3 к, R6 - 4.7 к, R7 - 5.1 к, R8 - 1 к, R9 - 15 к, R10 - 910 к, R11 - 1 к, R12 - 9.1 к, C1 - 330 nF, C2 - 150 pF, С3 - 100 F/25V.

For the PSU

R13 - 360 к, R14 - 56 /0.5 W, C4 - 330 nF/400 V
D6 - Д814В.

All you need for making this project is in the zip


Insect.zip

 

[Dazza]

I have a circuit for a mosquito repellor, in a book for getting started into Electronics. I haven't tried it so I don't know if it works. I will scan it and post it.

 

[Dazza]

mosquito repellor

View attachment 35798

 

[audioguru2]

Hi Dazza,
Thanks for posting your circuit.
Do they still make unijunction transistors? I haven't seen one for nearly 40 years!
I worry about how little sound output that an ordinary loudspeaker will produce at 22KHz. Most expensive hi-fi tweeters have difficulty reaching 20KHz.
The impedance of the loudspeaker will be much higher than 8 ohms because of its inductance, causing a poor match to the transformer.
Will that transformer pass 22KHz? It has capacitance on its windings creating a filter.

 

[ante1]

Audioguru,

The mosquitos have much better hearing than you and I so there is no need for 120db for them to hear it. ;D ;D

 

[Vedran1]

??? :

Mosquitoes as i learned in school just sense what we breath out (CO2) and they cant be disturbed by any sound no matter how many db is sound you are playing to them ;D ;D ;D

I watched that on some documentary film also.... if I am wrong ok....

Vedran

 

[audioguru2]

Hi Vedran,
Yeah, those expensive propane-powered mosquito catchers produce a huge cloud of CO2 and suckin the mosquitoes that are attracted to it.
I think that they are also attracted to our heat and odour, so that they don't try to suck blood from the chairs that we are sitting in. The experts say that they are also attracted by bright, coloured clothing.
If mosquitoes are deaf, then who came-up with the crazy idea of repelling them with an electronic ultasonic circuit that feeds its sound from a speaker that can't produce it, through a transformer that doesn't match the speaker nor pass the signal?