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Schematic to breadboard

Discussion in 'General Electronics Discussion' started by Chr1s, Dec 20, 2016.

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  1. Chr1s

    Chr1s

    27
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    Dec 20, 2016
    Hi

    I am really struggling trying to take a schematic to breadboard. Could someone please help me with the connections? Do the collectors of the transistors connect to +5v and for the LM386N, do pins three, four and seven all connect together ?. Any help would be much appreciated

    Clipboard01.jpg

    Thanks


    [Mod edited to show schematic in the thread]
     
    Last edited by a moderator: Dec 21, 2016
  2. (*steve*)

    (*steve*) ¡sǝpodᴉʇuɐ ǝɥʇ ɹɐǝɥd Moderator

    25,271
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    Jan 21, 2010
    No, and no.

    The collectors don't connect to each other so even if one connected to +5v, the other would not.

    Pins 3 and 4 connect to ground. Pin 7 connects to a capacitor (the other end of which kind to ground).

    The simple rule is to follow where the lines go. Remember that crossing lines don't join unless there is a join shown by a dot.
     
  3. Chr1s

    Chr1s

    27
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    Dec 20, 2016
    Thanks steve. I guess I was following those rules but was a little confused about the transistors but now I see that the resistors are setting the voltage for the collector of the transistor. Is this correct?
     
  4. (*steve*)

    (*steve*) ¡sǝpodᴉʇuɐ ǝɥʇ ɹɐǝɥd Moderator

    25,271
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    Jan 21, 2010
    Well, the resistors R1 and TM1 are in series with the power connected to the circuit of T2 and there is also an inductor in series between them and the collector of T1.

    It isn't correct to say they set the voltage for these transistors, it's a bit more complex than that. I also don't like the biasing of T1, it would not be my choice. I think the design is based on magic because the antenna is essentially connected to the collector of T2 as well.

    Where did this circuit come from?
     
  5. Chr1s

    Chr1s

    27
    2
    Dec 20, 2016
  6. Audioguru

    Audioguru

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    Sep 24, 2016
    Some Instructables are designed by kids who are only 10 years old and know nothing about electronics.
    T1 is turned on and acts like a diode. Since T1 is turned on then T2 is turned off and does nothing.
    With T1 acting like a diode then the circuit is a very simple "crystal" AM radio.
    The magazine article said that the transistors are a Colpitts (spelt wrong) oscillator so then the circuit is called a regenerative receiver.

    How is this horrible "FM radio" tuned to a station? The variable capacitor does not have a parallel inductor and the inductor does not have a parallel capacitor.
     
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