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Clapper circuit that actually works?

  1. Nov 12, 2012 #1
    Hey guys. I've been trying to make a simple clapper circuit that turns a LED on and off, obviously with a clap. I've tried countless models I have found online and none have seemed to work.

    Has anyone here used an online model that has actually worked for them? Could anyone give me the link to said model?

    Thanks.
     
  2. jcsd
  3. Nov 13, 2012 #2

    Simon Bridge

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    Define "works".

    Though, to be fair, I don't think I've made one off the internet.
     
  4. Nov 13, 2012 #3
    One that actually turns the LED on and off with a clap. None of the models ive tried have done even that.
     
  5. Nov 13, 2012 #4

    Simon Bridge

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    Intreguing - They are all pretty much comparator circuits and some sort of sensor -
    haven't found one that doesn't do it's job. My usual problem is that they are either over-sensitive and go off at the slightest thing or under sensitive and you need to be right near them.

    I'd work on understanding the one you've got rather than look for another one ... though you could buy a commercial one and take it apart.
     
  6. Nov 13, 2012 #5

    NascentOxygen

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    What are the URLs for some that you've tried?
     
  7. Nov 13, 2012 #6




     
    Last edited by a moderator: Sep 25, 2014
  8. Nov 13, 2012 #7

    NascentOxygen

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    Two of these look like they should work without much trouble. (Skip the one that uses transistors.) Are you wanting it to do anything in particular, or just a demo where you'll learn by construction?

    It would be a big help to have a multimeter (voltmeter) on hand while trying to troubleshoot the constructed circuit.
     
    Last edited by a moderator: Sep 25, 2014
  9. Nov 14, 2012 #8
    It is actually a project for my electronics laboratory. We tried all three and for some reason the circuit doesn't work. What it does is just turn on the LED when the batter is connected to the circuit. Maybe I should try different resistors or something of that sort.
     
  10. Nov 14, 2012 #9

    NascentOxygen

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    Many circuits won't work without tweaking, possibly because a component differs a little from the one the original constructors used. You need to test each block to make sure it is working, before expecting them to all work together.

    Have you got one constructed and ready to examine?
     
  11. Nov 14, 2012 #10

    Simon Bridge

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    As the 1st video suggests - putting a pot in the voltage divider (on the comparator) will allow you to adjust the sensitivity. You could also put a pot on the amplifier side to make the signal input to the comparator louder. You should check that each stage in the circuit does what it is supposed to do separately.

    I'm thinking that a common mistake with these things is to swap the v- and v+ pins ... if the sensitivity was low, then the circuit would look properly wired but it won't be. If you increase the sensitivity, the LED will go out when you clap.
     
  12. Nov 14, 2012 #11
    I don't have any circuit set up right now since Ive been going back and forth between the ones I find online, but I'll try again tomorrow. Which one of these models seems more adequate to work? The first one?
     
  13. Nov 14, 2012 #12

    NascentOxygen

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    Yes, the first one looks okay. The third one requires two claps, to first turn the LED on, then off.
     
  14. Nov 14, 2012 #13
    My group and I built the first one without flip flops or timer. We get a tiny little bit of light from the LED with every clap. I assume we should put less resistances so more current passes through them and the LED can light up better?
     
  15. Nov 14, 2012 #14
    Elektor had some designs to do that. What they propose uses to work and be sound.
     
  16. Nov 14, 2012 #15

    NascentOxygen

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    I'd say no, heavier LED current may not be the answer. For an indicator LED it is already powered at about its current limit. It might be the first stage that requires attention. Breadboard it again and we'll take a look at it.

    For claps it will blink on briefly, as in the video. But if you howl or whistle at it, the LED should light for the duration.
     
  17. Nov 14, 2012 #16

    Simon Bridge

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    I'll second that - the peak current will likely be the max the LED can handle. A comparator is usually very sensitive to small changes in input giving an output that switches rapidly on and off. What would a rapidly oscillating signal mean for the brightness of the LED?

    Smoothing out the output signal (hint: negative feedback) should help as will buffering the output and/or just making the circuit less sensitive (so the trigger voltage is well below the small oscillation in the triggering signal. As per post #2: understanding the circuit is the key to getting it to work well: I suspect that is why this exercise was selected.

    (note: the videos you linked actually explain all this to different degrees - and looking up "comparator" online also gets you these details. In a way the exercise is trying to get you to read resources in a special way: so that you realize the implications of what you read.)
     
  18. Nov 14, 2012 #17

    vk6kro

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    I have designed and built circuits that control a transmitter so that it turns on when a microphone detects speech.

    It consists of an amplifier to build the output of a microphone up to 5 volts or so (from 10 mV) and this drives a monostable which has a delay of several seconds.

    So, only a brief pulse is needed to produce continuous output for any desired length of time.

    This would allow a LED to turn on and be easily seen.

    I guess I could find this circuit, but similar circuits probably exist on Google Images. Just look for the monostable (typically a 555 chip or maybe a LM121 chip).
     
  19. Nov 16, 2012 #18

    NascentOxygen

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    If you construct it again, can you remove the microphone and its 1kΩ resistor, then power the circuit and use a voltmeter to measure the voltage at each of these points (referenced to ground): A, B, C, D, and E. Post the values here.

    Then use a short wire to connect the two points x-x and remeasure voltages A, D, and E (again referenced to ground).

    You are using an LM324? Does your microphone element have a manufacturer or part number on it?
     

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