Help With Simple Circuit

Discussion in 'General Electronics Chat' started by tim.brayshaw, Jun 24, 2012.

  1. tim.brayshaw

    Thread Starter New Member

    Jun 24, 2012
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    Hi there,

    I am trying to fix one of those stuffed toys which talks and things and wondering if you could help me rewire it, some of the components have been ripped out - switch, motor and speaker.

    Basically, when you activate the circuit the first time, the speaker activates and the stuffed toy makes a noise.

    The second time you do so, it activates the speaker, and then a motor activates to vibrate.

    Below is a picture of the circuit with only the power leads in the correct position.

    Is it possible for anyone to help me see where the two wires for the motor go, two wires for the switch to go, and two wires for the speaker to go?

    From the state of the wires i can tell that the brown cable from the speaker attaches to the Base leg of the transistor in the bottom left of the image of the cicuit board.[​IMG]

    Thank you.
     
  2. cork_ie

    Member

    Oct 8, 2011
    348
    58
    It looks like the speaker goes into the corner between R2 and C1. The 0 1 marking looks like the old DIN speaker symbol which is a Square 0 and a line indicating speaker + & -. If you can post a photo of the underside view of the PCB and any numbers on the transistors I'm fairly sure I can work out the circuit and help you.
     
  3. KJ6EAD

    Senior Member

    Apr 30, 2011
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    It's easier to view a PCB right side up and straight on.
     
  4. tim.brayshaw

    Thread Starter New Member

    Jun 24, 2012
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    Cheers for the reply.

    Right, the black transistor in the top left of the image above says S8550 / E512 and the transistor in the bottom left of the image above says S8050 / D116. The orange circle says 104 on it.

    Here is a picture of the underside of the PCB with the brown cable (+) of the speaker connected to where it was originally.

    Love to hear how the motor, switch and speaker is connected to this circuit. Not amazingly knowledgeable as far as circuitry goes, so be forgiving when you reply.

    Thanks Again.

    [​IMG]
     
  5. cork_ie

    Member

    Oct 8, 2011
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    Sure if you don't have an IC on the underside buried under that black dot.

    I am trying to see how the discreet components are connected on the board.
     
  6. tim.brayshaw

    Thread Starter New Member

    Jun 24, 2012
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    Do you need anymore information from the board at all, shall I look under the black dot?
     
  7. tim.brayshaw

    Thread Starter New Member

    Jun 24, 2012
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    Well, I've just thought. Is that integrated circuit something to do with the sound that comes out of the speaker? Or the fact it cycles through two behaviours? Sound only, and sound and motor start.
     
  8. KJ6EAD

    Senior Member

    Apr 30, 2011
    1,425
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    That black blob is epoxy and has a silicon die under it that contains most of the circuitry for your toy. Don't disturb it.

    Look up COB (chip-on-board) in Wikipedia if you're curious.
     
  9. tim.brayshaw

    Thread Starter New Member

    Jun 24, 2012
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    Thanks KJ6EAD, noted, I won't mess with that. Might read up on it, I know how to solder and such, would love to know enough so I know where these components go. Time will tell I guess.
     
  10. WBahn

    Moderator

    Mar 31, 2012
    17,737
    4,789
    You might be interested in The Great Furby Autopsy. In the furby, all of the behaviors were controlled by a single shaft and how it worked as just that each activation cycled the shaft through part of a revolution corresponding to one distinct behavior. The next activation rotated it through the next behavior, and so on.

    In your case, the IC under that blob probably has a program that cycles through what is known as a finite state machine (FSM) that behaves in an analogous way.
     
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