How this piece of alarm clock circuit works?

Discussion in 'General Electronics Chat' started by praveenmax, Apr 26, 2016.

  1. praveenmax

    Thread Starter New Member

    Apr 26, 2016
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    Hello all,
    I have ripped a small circuit off my alarm clock. I want to learn how the music tune is played whenever the alarm time is reached.
    Please see the images I have added.Could someone please explain or give a brief idea on what this circuit contains & what it basically does?
    Sorry if this question seems too vague but I am basically a software programmer with no exposure to electronics/electrical stuffs. Just curious to know.
    Thanks...
     
  2. ErnieM

    AAC Fanatic!

    Apr 24, 2011
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    There is some sort of computer chip under that black blob, which is there to cover a bare die chip placed directly on the board. The die is not in a conventional package but placed directly on the board, then each connection has a tiny wire welded down. It is complicated but cheaper that using chips in high volume applications.

    Unless you sneak into the factory that makes these you will never know what that chip is.

    Google "sound chip" or "sound module" and you will find lots of similar devices.

    And welcome to the forums!
     
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  3. ericgibbs

    AAC Fanatic!

    Jan 29, 2010
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    hi p,
    As Ernie's pointed out, its a COB [ Chip On Board]

    The semiconductor 'die' is under that black blob.
    E
     
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  4. Tonyr1084

    Active Member

    Sep 24, 2015
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    The COB is probably some sort of read only memory. When the alarm clock reaches a set time (set by the user) it triggers a switch that turns on the little board you have. Whatever was pre-programmed onto it will play. Just like those greeting cards that when you open the card a battery makes contact and the card plays "Happy Birthday" or whatever musical format file is loaded onboard.

    I've seen them with Rosan Rosanna Danna (from Saturday Night Live) and Lucy Ricardo doing something silly from one of her TV shows. All the board does is play that file when it's powered. You'll have to test the alarm clock for voltage when the alarm is triggered. Then you can use the COB for some gag or something.

    For April Fools day (years ago) I put the guts from a card under my boss's desk. When he opened the drawer the music played. It was good for a laugh.
     
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  5. praveenmax

    Thread Starter New Member

    Apr 26, 2016
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    Oh, then I guess the chip would damage if I try to pull the die. Btw, thanks for the warm welcome :)
     
  6. praveenmax

    Thread Starter New Member

    Apr 26, 2016
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    So, Can I connect a battery to any two of those 3 wires and make it to play the audio??
     
  7. dannyf

    Well-Known Member

    Sep 13, 2015
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    Not
    Only that, if you connect the right battery the right way at the right time, it will also mix your drinks, do your laundry, ... For you.
     
  8. Tonyr1084

    Active Member

    Sep 24, 2015
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    Before you connect any power sources to the board I'd suggest you take the alarm clock (hopefully you still have the working remains) and see what kind of output you get where those wires were connected.

    I have no idea what you'll find, but I'd expect to find (most likely - but no guarantee) a DC source of some voltage. Make sure you understand the voltage and polarity. Otherwise, trying to hook up a power source could end up ruining the COB. Keep in mind you may even see an AC signal there. AND it's possible (AC or DC) the third wire may be some sort of timing signal. By that I mean it may be a clocking signal that drives the chip to play at a certain speed.

    What is it you want to do with the board?
     
  9. praveenmax

    Thread Starter New Member

    Apr 26, 2016
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    Thanks for the info. I just started to tinker with electronic stuffs and I was trying to play my favorite alarm tune from this circuit.
     
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