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Variable frequency sound emitter

Discussion in 'General Electronics Discussion' started by taylor, Jul 3, 2012.

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  1. taylor


    Apr 12, 2012
    Hi all,

    Part of a circuit I'm working on now for a model rocket launcher ignition system has 1 buzzer that sounds when the launch button is pressed. I'm thinking about adding another buzzer that sounds at two different frequencies back to back (low -> high) when the system is started.

    here is my circuit as it stands:

    I would like to have the 2 tone buzzer sound after the first switch (key switch/S1 in the schematic) is closed to signal that the system has started. What would I need to accomplish this? Would it have to be some kind of logic gate that allows 2 different voltages to flow to the buzzer? I'm very new to electronics so forgive me if I sound markedly uneducated :p

    As you can see the supply voltage is 12v.

    edit: in case you're wondering the load resistance at the end is the ignition load
  2. KJ6EAD


    Aug 13, 2011
    There are many ways to do it. I might try to use two 556 dual timers or even a single 558 quad timer. That would give a total of four timers. The first timer would be configured as a monostable to set the duration of the sound by enabling/disabling the second timer which would alternately enable/disable the third and fourth timers that are configured as astables (oscillators) to produce the high and low tones.

    For more information, research the 555, 556 and 558 timers.
    Last edited: Jul 4, 2012
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