Using 3.5mm audio signal to trigger a buzzer

Discussion in 'The Projects Forum' started by Jakey69, Oct 12, 2011.

  1. Jakey69

    Thread Starter New Member

    Oct 12, 2011
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    Hi all, I might be approaching this the wrong way - so I will explain the whole situation in-case you can think of a better way to help!

    So - we have a system in place at work that 'beeps' when a new order comes in to the store. Unfortunately this 'beep' is being drowned out by background noise and it's hard to hear the 'beep'.

    the beep is played through a non-powered speaker through a 3.5mm audio jack.
    Why not use a powered speaker, you ask? Well - we've been told by the software company that we cannot - and yes - we've tried using one anyway and for some reason the beep just will not play through the powered speaker - only a non powered one! crazy right!

    Anyway - what I want to do is wire up a 'buzzer' to the 3.5mm jack and potentially use USB power to power the buzzer, having the 'beep' trigger the buzzer.

    buzzer in question - http://jaycar.com.au/productView.asp?ID=AB3452

    Now I don't suppose I can just daisy chain all three components (buzzer = USB 5v = 3.5mm = buzzer) and expect this to work (5v from USB might fry something going through the 3.5mm jack?) ?

    How would I be-able to wire this up? Or how else could I get this to work?

    Thank-you for any advice in advanced.

    Jake
     
  2. Audioguru

    New Member

    Dec 20, 2007
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    The tiny buzzer will probably not be heard if you manage to get it to work.
    We have no idea of the circuit that can directly drive a little speaker but cannot drive an amplified speaker. Maybe it needs a DC load?
     
  3. Jakey69

    Thread Starter New Member

    Oct 12, 2011
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    well I have no idea either! it's so strange, a powered speaker only makes a 'click click' noise, yet unpowered is a (faint) beep.

    Ahh yes - 79db is that buzzer, definitely not loud enough. Is there anything I should be looking at that can be powered from USB? or should I get a 12v adaptor and run something more beefy?

    This thing doesn't need to provide ear peircing sound levels - but I'd imagine a volume similair to a phone ringing would suffice.
     
  4. Adjuster

    Well-Known Member

    Dec 26, 2010
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    Seems likely enough: quite possibly terminating the signal in a low resistance roughly equal to the un-powered speaker impedance and blocking any DC with a capacitor would allow a powered speaker to be used, but if so I am surprised your suppliers did not suggest this.

    Bear in mind though that you may be held responsible for the effects of any modifications or adapters applied to your employers' equipment, whether using buzzers, dummy loads or otherwise. If anything goes wrong you could be sanctioned by your employer or made to pay damages.
     
  5. Jakey69

    Thread Starter New Member

    Oct 12, 2011
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    so would this work like a daisy chain or am I dreaming? (buzzer = USB 5v = 3.5mm = buzzer)
    supposing buzzer was something louder than a buzzer, of course :p
     
  6. Audioguru

    New Member

    Dec 20, 2007
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    If the signal produces a low sound in a speaker then it certainly will not drive a buzzer.
    Adding 5VDC might not make any difference but the new buzzer might turn on during the first beep then turn off during the second beep.
    Adding 12V might blow up the signal source.
     
  7. Jakey69

    Thread Starter New Member

    Oct 12, 2011
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    would it be difficult to set-up a circuit to make the buzzer pulse while there was a beep?

    edit: would it be hard to set up the USB to power the buzzer and the 3.5mm act as a switch/trigger instead of it being daisy chained? I think this is how a relay works?
     
  8. Butterworth

    Active Member

    May 6, 2009
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    If the signal from the 3.5mm jack is significant enough, why not plug it into an amplifier circuit, something simple that would boost the signal to drive a larger (more powerful) buzzer?
     
  9. Jakey69

    Thread Starter New Member

    Oct 12, 2011
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    Do you care to go into more details please?
     
  10. Adjuster

    Well-Known Member

    Dec 26, 2010
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    The OP has apparently tried a powered speaker without success - see earlier posts. Whether this is for want of a DC return or some other reason, we do not know.

    The OP has suggested some kind of relay (presumably electronic) to drive a buzzer. This may work, but more information is required about this mysterious signal that "won't work a powered speaker". Without such information we can debate this forever.
     
  11. Jakey69

    Thread Starter New Member

    Oct 12, 2011
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    What information would you require? I wish I could give you more details!

    When a non-powered speaker is plugged it is a very faint 'beeeeeep' when a powered speaker is plugged it is a very loud (obviously depending on volume of amplification) CLICK CLICK CLICK (a bit like a gun).

    how would I wire a circuit to use the passive beep as a trigger? or should I concentrate on something else?
     
  12. Adjuster

    Well-Known Member

    Dec 26, 2010
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    Technical information, such as what voltage is developed into an open circuit or high impedance like the input to your powered speaker, and what voltage is delivered into the ordinary un-powered speaker. I realise that you are unlikely to have an oscilloscope handy, and that you may not be familiar with such matters, but even AC and DC readings taken with a multi-tester (DMM) would likely help.

    There is a suspicion that the powered speaker fails to work because it does not supply a sufficiently low resistance return path for DC current. The CLICK CLICK CLICK sound you describe is strongly suggestive of this, but not conclusive. Measurements such as I have described might cast more light on this.

    You could of course try making up a coupling adaptor on the basis of the DC current hunch, say with a 33Ω resistor load (or perhaps 10Ω if you are sure that the un-powered speaker is an 8Ω model). An un-polarised coupling capacitor of maybe 1μF could then take the signal on to an amplifier, but actually this could easily do harm: for instance, once the DC path was completed the signal might be far too big for your amplifier input. It would be best to know how much signal you have before connecting up.
     
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