555 timer mosquito repellent

Discussion in 'The Projects Forum' started by Malimujo, Jul 27, 2016.

  1. Malimujo

    Thread Starter New Member

    May 26, 2013
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    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 =)
     
  2. jpanhalt

    AAC Fanatic!

    Jan 18, 2008
    5,676
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    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
     
  3. Malimujo

    Thread Starter New Member

    May 26, 2013
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    Here it is the schematic. And if it is 3,8 khz i would still have to be able to hear the speaker beeping
     
  4. Dodgydave

    Distinguished Member

    Jun 22, 2012
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    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.
     
  5. Malimujo

    Thread Starter New Member

    May 26, 2013
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    COuld you edit my schematic plz i am not shure what are you thinking ?
     
  6. AnalogKid

    Distinguished Member

    Aug 1, 2013
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    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
     
  7. wayneh

    Expert

    Sep 9, 2010
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    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.
     
  8. AnalogKid

    Distinguished Member

    Aug 1, 2013
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    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
     
    wayneh likes this.
  9. absf

    Senior Member

    Dec 29, 2010
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    Just remove the blue wire and add in the red wire...

    555 mosq.jpg
    Allen
     
  10. DickCappels

    Moderator

    Aug 21, 2008
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    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?
     
  11. Alec_t

    AAC Fanatic!

    Sep 17, 2013
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    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.
     
  12. Malimujo

    Thread Starter New Member

    May 26, 2013
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    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
     
  13. Willen

    Member

    Nov 13, 2015
    138
    12
    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!
     
  14. GopherT

    AAC Fanatic!

    Nov 23, 2012
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    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.
     
  15. Willen

    Member

    Nov 13, 2015
    138
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    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.
     
  16. GopherT

    AAC Fanatic!

    Nov 23, 2012
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    It seems like Dow Chemical may not be advertising this in your neighborhood.

     
    Willen likes this.
  17. shortbus

    AAC Fanatic!

    Sep 30, 2009
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    Because you guy's are smarter? Or your mosquitoes are hard of hearing and the 'electronic repellents' don't work on them? :)
     
  18. wayneh

    Expert

    Sep 9, 2010
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    "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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