circuit with timer or other way?

Discussion in 'The Projects Forum' started by nathanimate, Nov 22, 2007.

  1. nathanimate

    Thread Starter New Member

    Nov 22, 2007
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    Hi all.
    I have a project to do but got really confused so I am looking for your precious help.

    An mp3 is connected to speaker(s). The mp3 must always be on so it is powered by its own battery. The portable speakers have an own battery power source as well. The circuit leading from the mp3 output to the speakers opens and closes by a normal switch. When the circuit is closed, sound must only be heard for about a second but then it must stop, even if the switch is still closing the circuit. To listen to the sound again, you must reopen and reclose the switch. How do i make the sound stop after a second, but be able to repeat the process?

    Thank you
    Nathan
     
  2. thingmaker3

    Retired Moderator

    May 16, 2005
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    You'll need something in addition to just the switch.

    For example, your could instead use a pushbutton to trigger a 555 monostable which in turn controls a relay or solid state switch. The speakers would play for one second when the button was pushed.

    Or... you could use an on-off switch to charge a capacitor when on - allow the capacitor to discharge through a resistor when the switch is turned off.
     
  3. iONic

    AAC Fanatic!

    Nov 16, 2007
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    What is the voltage of the MP3 player and the Speaker power?
     
  4. nathanimate

    Thread Starter New Member

    Nov 22, 2007
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    mp3 voltage: 1.5V
    speakers: 3V or 6V if stereo
     
  5. iONic

    AAC Fanatic!

    Nov 16, 2007
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    Wow....low! 6V is near the low end for the operating voltage of the LM555 timer.
    And a relay might draw more power than needed. It would be nice to uses an optoisolator instead of the relay.
     
  6. thingmaker3

    Retired Moderator

    May 16, 2005
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    Low end for most MOSFET 555s is 3 V. ICM7555 from Intersil and TLC555 from T.I. both will run on 2 V. I don't know of any which could run from the MP3's 1.5V, but the speaker supply should handle most 555s with no trouble.
     
  7. nathanimate

    Thread Starter New Member

    Nov 22, 2007
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    The mp3 will always be on and in a circuit of its own. I will just be controlling the speakers' circuit.
     
  8. thingmaker3

    Retired Moderator

    May 16, 2005
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    To clarify, can you use a different switch, or must you use the one described in your opening post? If it must be a specific switch, please tell us what kind (i.e. SPST, DPDT, etc.).
     
  9. iONic

    AAC Fanatic!

    Nov 16, 2007
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    What exactly is the purpose of a 1 Sec delay before turning off the speaker circuit?

    Also, How many components(circuits) do you have..

    MP3--->Speakers? or
    MP3--->Switch--->Speakers?
     
  10. nathanimate

    Thread Starter New Member

    Nov 22, 2007
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    There are two circuits and two switches. The mp3 circuit is independant and is not affected in any way. It stays closed (on).
    I want to affect the circuit starting from the mp3 audio output and going to the speakers. The speakers have their own power, which is 2xAA batteries each. I can use one or two speakers, it doesn't matter. I am not affecting the power supply to the speakers; again that is always on. I am only affecting the signal from the mp3 player to the speakers.
    The actual switch opening and closing the circuit (mp3->speakers) can be any switch. The whole purpose of this action is to force people to re-open and re-close this switch. I don't want a non-stop signal to the speakers with the circuit closed. The delay of ~1sec is to allow for enough sound to be heard, before having to re-open (and re-close) the switch.

    I hope this clarifies things and I apologise for not being clear enough:)
     
  11. Ron H

    AAC Fanatic!

    Apr 14, 2005
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    As others have said, there are CMOS 555 timers which can easily handle your one second on time.
    I researched low on-resistance analog switches, and there are a lot of different ones available from several different manufacturers which will handle the audio to the speaker(s), in various switch configurations. They are designed for cell phone use, and as such are in tiny surface mount packages. Are you able to handle these? Some are even in packages where the connections are totally hidden under the package, which means they must be soldered down in a reflow oven (can't use a soldering iron). Even the ones that do have protruding leads require special soldering techniques. Do you have these skills, or should we look for another solution?
     
  12. iONic

    AAC Fanatic!

    Nov 16, 2007
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    Bizarre! If both the MP3 player and speakers stay on, draining power, then why do you want some intermediary switch to cut the sound. Why not just turn the speakers off. Any why you want someone to press a switch to stop the sound following a 1 second delay, then press a switch to turn the sound on again for no apparent reason is beyond me. I must have bumped my head or something cause I can't figure it out. Where does the MP3 input go, to one speaker?, to a base unit that goes to the 2 speakers?
    Is there a power switch on the speakers?
     
  13. thingmaker3

    Retired Moderator

    May 16, 2005
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