circuit to a beep with a switch is pressed

Discussion in 'The Projects Forum' started by jjarosz, Oct 19, 2011.

  1. jjarosz

    Thread Starter New Member

    Oct 19, 2011
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    Hi Everyone,
    I've looked through many of the threads on this and think a 555 might be the way to go, but haven't seen anything exactly like what I am looking for.

    Basically, I'm looking for a circuit to make a short beep (maybe 1 second or a half second) when a switch is pressed each time. The switch I'm using is a push on-push off switch..so basically, I want a short beep when I turn the power on, and also short beep when I turn the power off..

    I'm hoping that makes sense...any help is appreciated.

    Joe
     
  2. KMoffett

    AAC Fanatic!

    Dec 19, 2007
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    The circuit want is an "edge detector". What is the power source?

    Ken
     
  3. MrChips

    Moderator

    Oct 2, 2009
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    Ok, you have asked for three different things:

    1. A short beep (half-second) when the power is turned on.
    2. A short beep when a button is pressed.
    3. A short beep when the power is turned off.

    Is that correct?

    (Keep in mind that for #3 the power is off).
     
  4. Bernard

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    Aug 7, 2008
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    Use two 555's, one for length, other for frequency. A 1/10 sec @ 1 kHz makes a nice chirp. Use a large cap to supply power for off chirp.
     
    Last edited: Oct 19, 2011
  5. KMoffett

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    Dec 19, 2007
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    I think this will give you what you were describing. The operation will depend on the tone module (Sonalert) and voltage of the host circuit. Adjust C1 and R1 for the desired effect.

    Ken
     
  6. jjarosz

    Thread Starter New Member

    Oct 19, 2011
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    Hi Ken, the power source is 3 AAA batteries, so 4.5vdc.
     
  7. jjarosz

    Thread Starter New Member

    Oct 19, 2011
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    Probably my bad explaining it. The button is the on-off power, so when you push the button (which turns the power on) it makes a short beep. Then when you push the button again (which turns the power off) it makes a short beep. So essentially an audible tone when turning on or off via a switch. Sorry it wasn't clear earlier.

    Joe
     
  8. MrChips

    Moderator

    Oct 2, 2009
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    Joe, sorry, my mistake. I did not read your post carefully enough.

    OK, it can be done. What kind of beeper do you plan on using?

    It can be:

    1) a typical 8-ohm loudspeaker
    2) a piezo transducer
    3) a 5V buzzer (maybe 4.5V)

    How loud does the sound have to be?
     
  9. jjarosz

    Thread Starter New Member

    Oct 19, 2011
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    I would be using a piezo. thank you for the help....
     
  10. KMoffett

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    A discrete Piezo element (requires an external oscillator) or a Piezo sounder? And what is the current drawn by the load that the switch is used to switch on and off?

    Ken
     
    Last edited: Oct 20, 2011
  11. Bernard

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    Is the switch SPST or SPDT. IF double throw it would make life much easier.
     
  12. KMoffett

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    I think a DPST.

    Ken
     
  13. jjarosz

    Thread Starter New Member

    Oct 19, 2011
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    Hi Ken, not sure why I didnt get a notify on your response, apologies for the delay..

    I would use a discrete element. The draw is minimal. Essentially just used to switch on and off an LED which is used as a visual indicator.
     
  14. KMoffett

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    A discrete Piezo element will require additional components for an oscillator to drive it. How loud must the tone be? Can you use the DPST switch, or are you limited to an SPST?

    Ken
     
    Last edited: Oct 23, 2011
  15. KMoffett

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  16. jjarosz

    Thread Starter New Member

    Oct 19, 2011
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    it doesnt need to be all that loud. a DPDT is fine also
     
  17. ElectroDFW

    New Member

    Sep 2, 2011
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    Hi,

    This circuit has been helpful to me.

    Note: this is not my own design, i received it from a very helpful member on the electronic-circuits-diagrams.com forum from member 'pebe'.
    here is what he told me about the circuit:
    ---------------
    BEGIN QUOTE
    ---------------
    This circuit should do what you want. Only one of the four XOR gates of the CD4070 is used. Its logic is that if the two inputs are both high or low, then the output is low. But if one of the inputs changes state then the output will go high.

    With SW open, points A, B, and C will all be high and the output will be low. C1 will be charged via R1.

    When SW closes, A goes low. B will go low but C will stay high for 1/2 sec until C1 discharges. During that time the output will go high. As soon as C1 has discharged so B and C are both low, the pulse will end.

    The same thing will happen as the switch is opened again.

    Tie the 6 unused inputs to either 0V or V+ as convenient. Leave the 3 unused outputs unconnected.

    Check on the data sheet for pin connections and chack the gate will supply the current you need.

    Best of luck.
    -------------
    END QUOTE
    -------------

    What I found when hooking it up is to power it in parallel with your main circuit and a circuit that sounds whatever alert you want to use, *if* it triggers with a positive pulse. If you need a negative pulse, use the other circuit. if you need a longer or shorter pulse, play with the resistor/capacitor values to achieve the desired timing.

    Regards,
    David
     
  18. KMoffett

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    Dec 19, 2007
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    Both circuits are dual-edge detectors. You will get a pulse out on both the positive-going and negative-going edges of the input. They do differentiate whether you get a high or low pulse at the output. However if jjarosz wants to use this with a power switch, it has to be powered from the battery all the time.

    Ken
     
  19. jjarosz

    Thread Starter New Member

    Oct 19, 2011
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    now that I read this, that point about being powered all the time concerns me a little. I'm assuming that means it will consume battery all the time while its waiting for the trigger, shortening battery life, am I correct on that?
     
  20. KMoffett

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    Dec 19, 2007
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    Yes. Depending on the capacitor leakage and the quiescent current for the IC it can be very small. But...it will be a continuous drain.

    Ken
     
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