555 timer mosquito repellent

Thread Starter

Malimujo

Joined May 26, 2013
8
Hello,
I am building a mosquito repeller from 2 different circuits using a 555 timer and ultrasound, through a tweeter. I have a high school degree in electronics so I know a bit on it but not enough. The repellent is from this web page http://www.electronicshub.org/electronic-mosquito-repellent-circuit/ and im adding a transistor to be used as a switch (tip 122 or tt2194 ) like in this schematic http://circuitdigest.com/electronic-circuits/transistor-tester (the " A B C " part only). And it wont work I used a led and 0,1 uF capacitor to lower the frequency to 8 Hz so i can see if the circuit is working but the led constantly stays on so guess it does not work. For measuring equipment i have only a multimeter no oscilloscope to measure frequency.

I would be grateful for any advice on what to do or change in the schematic.

Thank you =)
 

jpanhalt

Joined Jan 18, 2008
11,087
Without seeing your actual circuit, it is hard to guess what's wrong. However, the circuit you post uses a 0.01 uF timing capacitor for 38 kHz. Increasing that to 0.1 uF will not reduce your frequency to 8 Hz. You frequency, if working, is more like 3.8 kHz.

John
 

Dodgydave

Joined Jun 22, 2012
11,284
Your resistor R2 is in the wrong place, it should be between pins 6,7.

For astable operating pins 2,6 are joined pins4,8 are positive, pin 1 negative supplies, with the resistors shown try a 100uf cap across the 0.01 on pins1,2. this should give a frequency of 3.8hz which should make the led flash.
 

AnalogKid

Joined Aug 1, 2013
10,986
Even though it is drawn very very badly, the transistor tester schematic is correct. The mosquito schematic is wrong, but the text description underneath it is correct.

BTW, there is almost zero valid data to indicate that ultrasonic repellents actually work outside a laboratory environment.

ak
 

wayneh

Joined Sep 9, 2010
17,496
BTW, there is almost zero valid data to indicate that ultrasonic repellents actually work outside a laboratory environment.
A lack of evidence is not evidence of lack. But yeah, I don't think these things actually work. They'd be much more widely used if they did.
 

AnalogKid

Joined Aug 1, 2013
10,986
Let me rephrase - over the last 30 years, no credible test facility has been able to produce repeatable, consistent, useful, positive results in outdoor conditions.

ak
 

DickCappels

Joined Aug 21, 2008
10,153
I live in an area where many people sleep under mosquito nets and dab themselves with chemicals but I have never seen any electronic mosquito repellents for sale. Why could that be?
 

Alec_t

Joined Sep 17, 2013
14,280
Have you calculated or measured the current drawn by your speaker? If you're using a PP3 battery as your power source I suspect its life will be disappointingly short.
 

Thread Starter

Malimujo

Joined May 26, 2013
8
Dont know the power draw, its a small 2,5 cm or 1" sony tweeter and I am planing to run it off a 9v battery for start maybe 9 v adapter later
 

Willen

Joined Nov 13, 2015
333
Hi Malimujo,
You have to investigate little in Google before making the mosquito repellent device. Some modern searchers found that the hearing ability of female mosquitos is not higher than 2 or 3KHz which pretty low in frequency than human being. If that's true, entire untrasonic mosquito repellent made around the world are just a wrong perception!
 

GopherT

Joined Nov 23, 2012
8,009
I live in an area where many people sleep under mosquito nets and dab themselves with chemicals but I have never seen any electronic mosquito repellents for sale. Why could that be?
I'm guessing a cultural thing. People in Thailand might shun all the possible audio frequency radiation and those nasty secondary harmonics required of electronic solutions in favor of safe, proven chemical remedies like methyl-ethyl-death. Also, those four poster beds used to support the net lets them feel like royalty.
 

Willen

Joined Nov 13, 2015
333
Around my village, houses and rooms are pretty open. Even I closed door and windows, there are many opening still. :) If I used chemicals evaporator or burn mosquito coils, chemical or smoke goes elsewhere from the openings and is not effective for repellent. So just one effective idea is to use net.
 

GopherT

Joined Nov 23, 2012
8,009
Around my village, houses and rooms are pretty open. Even I closed door and windows, there are many opening still. :) If I used chemicals evaporator or burn mosquito coils, chemical or smoke goes elsewhere from the openings and is not effective for repellent. So just one effective idea is to use net.
It seems like Dow Chemical may not be advertising this in your neighborhood.

 

shortbus

Joined Sep 30, 2009
10,045
I live in an area where many people sleep under mosquito nets and dab themselves with chemicals but I have never seen any electronic mosquito repellents for sale. Why could that be?
Because you guy's are smarter? Or your mosquitoes are hard of hearing and the 'electronic repellents' don't work on them? :)
 

wayneh

Joined Sep 9, 2010
17,496
"He said studies have shown ultrasonic devices do not repel mosquitoes and may even attract them."

From a Scientific American article linked to the Zika thread in the Off Topic forum.
 
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