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Help w/ Looping a Rec Module

Discussion in 'General Electronics Discussion' started by olaf1axe, Sep 28, 2011.

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  1. olaf1axe

    olaf1axe

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    Aug 25, 2011
    I'm putting together a project that needs background sound. I want to be able to record the sound and play it back continuously while the particular circuit is on. I'm using a $10.99 radioshack play/ rec module (9v/ 20seconds). Here's the link to the mod:

    http://www.radioshack.com/product/index.jsp?productId=2102855

    1) I want to know how I can make the circuit loop continuously while it's on so that it plays the same 20 seconds over and over until I flip the circuit's switch to off.

    2) These modules come with a rubber push button switch (like a calculator key) that you press and activate the sound with. I would like the sound to start when the switch has power not when someone pushes the button. I took off the rubber pushbutton and tried to solder the connectors on the circuit board but fried everything and it didn't work. Not sure how these switches work.

    Any ideas!? Help!!!
     
  2. KJ6EAD

    KJ6EAD

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    Aug 13, 2011
    If the 20 second period is fixed, not variable then you could just use an astable timer circuit to electronically "push" the button every 21 seconds. Usually the button is just sinking a logic line to ground. Both the timer and the playback module could be powered from the same supply so switching the supply on would activate both.

    There is a potential problem with this method though. If the module rejects start inputs during playback and the timing got out of sync, the timer would run and the module would not. I suspect that the module restarts on every button push regardless of status so this wouldn't be a problem.

    What happens if you just hold the start button down continuously? What happens if you push the start button during playback?
     
  3. olaf1axe

    olaf1axe

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    Aug 25, 2011
    Thanks KJ. I can physically lock the pushbutton in the on position and this would solve the play issue when powered. Still, I need the circuit to loop and repeat the sound as long as the circuit is powered. Is there some way to interrupt power for a second every so often? Maybe with a relay? That way when the circuit restarts and is powered up it begins to play again from the beginning...
     
  4. KJ6EAD

    KJ6EAD

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    Aug 13, 2011
    What happens if you just hold the start button down continuously. Does the message play repeatedly or just once? What happens if you push the start button during playback. Does it start again from the beginning or just continue playing?
     
  5. (*steve*)

    (*steve*) ¡sǝpodᴉʇuɐ ǝɥʇ ɹɐǝɥd Moderator

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    I think olaf1axe is telling us that if powered up with the button held down, it plays once and does not repeat.
     
  6. KJ6EAD

    KJ6EAD

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    I'd like to believe that but I want to hear it from him.
     
  7. (*steve*)

    (*steve*) ¡sǝpodᴉʇuɐ ǝɥʇ ɹɐǝɥd Moderator

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    If I were olaf1Axe I would have the button replaced with a link and the device powered from a 555 with a mark/space ratio such that the device is on for 21 seconds and off for 0.5 seconds (or thereabouts)

    My quick guess is that the required resistor and capacitor values will be approx 560k, 15k, and 47uF. Note that due to the relatively long period, the on time may be slightly longer, and not overly stable with temperature.
     
  8. olaf1axe

    olaf1axe

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    Aug 25, 2011
    Yes! Unfortunately the mod plays only once without repeating. Locking the pushbutton down would make it play when powered (perfect) but it wouldn't make it loop. As soon as it reached the end of the 20 second record period the sound would end and the button would still be down. If power were cut and then reconnected it would start playing again for another 20 sec cycle.

    Not super familiar w/ 555 timers though I understand the basic concept of what Steve is saying. Still it seem pretty tough to link anything to the pushbutton (its connectors are ultrathin and embedded in the circuit board).
     
  9. olaf1axe

    olaf1axe

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    Aug 25, 2011
    Could a capacitor or relay help by releasing power intermitently?
     
  10. (*steve*)

    (*steve*) ¡sǝpodᴉʇuɐ ǝɥʇ ɹɐǝɥd Moderator

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    What I was suggesting is to lock the button down and use the 555 circuit to power the device (the output of a 555 can provide significant current.

    Look up the 555 chip. I have given you the values you need for a suitable oscillator using this chip. It will effectively power it for 22 seconds or thereabouts, remove power for under 1 second, then start the cycle again.

    All you need do is make up the circuit (try it on a breadboard first) and connect the device between the 555 output and a supply rail.

    This does the trick of releasing power intermittently. (An no, a capacitor won't do it by itself).

    Another solution (far more expensive, but perhaps easier) is a time delat relay. If you can find one which operates off the same voltage as the sound playback device you may be OK. However it would be large, expensive, and a heavy draw on current compared with the sund playback device.
     
  11. olaf1axe

    olaf1axe

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    Aug 25, 2011
    Steve - The 555 timer works like a charm. Unfortunately, the pushbutton the initiates the playback must be pressed down each time in order to play the sound sequence. It only plays the sound sequence once. I don't know how I can locate the power circuit under the pushbutton in order to override it. Is this the end!? Remember I wanted playback to initiate with power on and then loop in order to be almost contnious. The loop is working but the power on playback is not. Thanks... Olaf.-
     
  12. olaf1axe

    olaf1axe

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    Aug 25, 2011
    Also... the pushbutton is a little weird. It has a silicon cover on the outside but the portion that makes contact with the circuti board does not seem to have any type of metal (it's a black almost rubber or silicon type surface that touches the contacts on the circuit board). What are these types of switches!?
     
  13. KJ6EAD

    KJ6EAD

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    There are only two switch contacts formed on the circuit board as interlaced traces. The conductive rubber pad on the chicklet key shorts the two switch contacts.
     
  14. (*steve*)

    (*steve*) ¡sǝpodᴉʇuɐ ǝɥʇ ɹɐǝɥd Moderator

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    OK, my understanding is that if you hold the button down (perhaps solder a link across the switch) then the device plays exactly once whenever power is applied.

    The idea of the 555 is to supply power to the circuit for 20ish seconds (to allow it to play), then remove power briefly, then apply power to get to to play again, and so on.

    You can tweak the on and off times as required to get almost continuous playback.

    Or am I not getting it somehow?
     
  15. jackorocko

    jackorocko

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    Apr 4, 2010
    He isn't using the 555 in a one shot setup?
     
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