Using PWM for a horn circuit

Discussion in 'General Electronics Chat' started by Popnfrsh24, Sep 24, 2010.

  1. Popnfrsh24

    Thread Starter New Member

    Sep 7, 2010
    5
    0
    Hey everybody,

    So I am needing to incorporate a horn on my RC car. I want to make it as simple as possible, so I was planning on using my PSoC micro and using a PWM output to drive a speaker. I don't need a very "clean" output so I heard that this is the way to go.

    I am getting confused on how to hook this circuit up. From what I have read, you take the PWM output and take it through a low pass RC filter. Do you then drive this speaker from the output of the RC filter? Does this low pass filter just get rid of the sharp transitions of the PWM output and make it more smooth?? And, since this PWM output varies from 0 - 5 V, wouldn't the DC voltage destroy my speaker? I really am looking for a solution that doesn't require a negative voltage. Here is the speaker that I am using

    http://www.mallory-sonalert.com/specifications/PB-2015W.pdf

    Also, what frequency should I set this PWM output as? Should I set it as the audible frequency that I want to hear coming from the speaker?

    Thank you,

    Joey
     
    Last edited: Sep 24, 2010
  2. Audioguru

    New Member

    Dec 20, 2007
    9,411
    896
    The little Sonalert speaker is not loud and produces only a high pitched beep of 1500Hz. It sounds nothing like a lower frequency car horn (but I remember that an old VW Beetle made a high pitched beep).

    The modulation is the frequency that you hear and this little speaker is tuned to produce only 1500Hz. The PWM frequency is much higher.

    Why use PWM? The little speaker can be driven from a little transistor with a 1500Hz square-wave input.
     
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