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The inaudible audible alert — Parallax Forums

The inaudible audible alert

trookstrooks Posts: 228
edited 2014-01-02 22:06 in General Discussion
I bet few here remember when Eisenhower was pres. For that reason few here will be having trouble with the little speaker thing that goes on a BoeBot. Sight gets blurred and hearing gets dimmed with age. For that reason I would like very much to have buzzer instead of the high pitched low volume pizeospeaker to signal me at various points in a program. Does anyone know of such a device that can replace the 'Barbie & Ken' speaker that came with the BoeBot? If all else fails I will simply reprogram and use an LED as my signaling device.

Comments

  • LoopyBytelooseLoopyByteloose Posts: 12,537
    edited 2014-01-01 08:46
    A buzzer can be powered pretty much the same as a relay coil with a 2n2222 transistor driving the transistors base. That should boost the power enough, and if the buzzer requires a higher voltage the 2n2222 acts as a level shifting interface.

    Personally, I have gotten weary of fiddly tiny 1/2 watt audio amps and such. If I want to do anything audio with the Propeller, I just drive a TIP120 Darlington that is connected to an 8 ohm 5 watt speaker and I get a blast of not so perfect.. but certainly loud enough audio.

    If one dislikes the tone, one can insert some low pass filtering to eliminate the high frequency harmonics of the square wave input.

    It is a down and dirty quick build, but I love it.

    Peter J recommends using an Max232 to drive a piezo electric speaker as it ups the overall power and you actual have several channels left over for an RS232 interface. That is another interesting option.
  • Phil Pilgrim (PhiPi)Phil Pilgrim (PhiPi) Posts: 23,514
    edited 2014-01-01 10:01
    For its size, the SoundPAL is pretty dang loud and requires no additional circuitry to use.

    -Phil
  • ercoerco Posts: 20,256
    edited 2014-01-01 12:14
    I like these 5V beepers for many reasons. Cheap, loud, small, self oscillating, just hook them to a micro pin and make it high. No freqout!

    http://www.ebay.com/itm/New-Arrival-Applied-Industrial-10-Pcs-5v-Active-Buzzer-Continous-Black-Color-Hot-/301021506088?pt=LH_DefaultDomain_0&hash=item461647aa28
  • LoopyBytelooseLoopyByteloose Posts: 12,537
    edited 2014-01-02 08:38
    Let's see a 5 volt beeper at 30ma is 0.15 watt of audio power versus my TIP120 and a 5 watts 8 ohm speaker that can provide 5 watts of audio.

    I don't think anybody really needs 20 watts or more, but 5 watts does allow you and a whole room full of people to hear the sound. I advice a volume control on the input side.
  • Phil Pilgrim (PhiPi)Phil Pilgrim (PhiPi) Posts: 23,514
    edited 2014-01-02 08:53
    What makes a bigger difference than the power output is the acoustic chamber the emitter is housed in. A 0.15W beeper in a suitable housing may well be louder than an unhoused 5W speaker.

    -Phil
  • ercoerco Posts: 20,256
    edited 2014-01-02 09:14
    @Loopy: Sometimes less is more. Those tiny beepers are surprisingly loud at 5VDC, like smoke detector loud. I usually leave the "remove after washing" sticker on or else I get complants from the family. But when powered directly by a micro pin, the impedance drops the volume to a more manageable level, I measured 11 mA draw when driven by a PIC run at 5VDC.

    IMO their best feature is they are self-oscillating. No freqout or overhead required. Just give them a high signal to turn it on and let your program get back to more important things.

    Heck, for just 18 cents apiece, I say give 'em a try. Free shipping, too.
  • LoopyBytelooseLoopyByteloose Posts: 12,537
    edited 2014-01-02 09:37
    Less is more, and more is less. -- Ludwig Mies van der Rohe

    http://en.wikipedia.org/wiki/Ludwig_Mies_van_der_Rohe

    And sometimes, more is more. It is just fun to have it loud. That little beeper may work fine, but a really loud sound will impress kids in a class demonstration.

    Maybe I am just loosing my hearing in my old age.

    I have some of the beepers here already. What I really like to have my Propeller make a sound like the bird in a coo-coo clock.... and loudly. People's eyes light up and they laugh.
  • ercoerco Posts: 20,256
    edited 2014-01-02 15:47
    BTW, I used that beeper here, driven directly by a 5V Picaxe pin, BTW: http://www.youtube.com/watch?v=ICAyUKGNldY

    I just got a wild hair to try tonight: putting a flashing LED in series with a beeper going to 9V. I'm hopeful that the beeper should either warble or toggle on/off with the LED. That combo would be useful as an easy "device active" warning alarm for the many flamethrowers I build and give away as gag gifts. I'd really hate for anyone to be accidentally surprised (God forbid harmed) by an accidental triggering.
  • ercoerco Posts: 20,256
    edited 2014-01-02 22:06
    erco wrote: »
    I just got a wild hair to try tonight: putting a flashing LED in series with a beeper going to 9V.

    It works, giving a click instead of a beep. Quick & dirty. I'll use this as a "power on" indicator in future flamethrowers, currently I use just a flashing LED.
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