Help with LM386 Amplifier Circuit

Discussion in 'The Projects Forum' started by droggie, Jan 12, 2013.

  1. droggie

    Thread Starter Member

    Oct 21, 2012
    137
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    I am trying to amplify my MP3 with the schematic pictured below. Can anyone tell me there are any errors?
     
  2. tracecom

    AAC Fanatic!

    Apr 16, 2010
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    C1 is not connected to R1, so there's no power on the IC. It is off one row.

    R2 is connected to itself.

    R3 is supposed to be a pot, not a fixed resistor. You can actually eliminate R3 and use the volume control on the MP3 player.

    R3 is connected to itself.

    You should print a copy of the schematic, and use a highlighter on the schematic for each component and wire as you install it. You also have some needless wires; use the component leads whenever possible. Color code the wires: red for +V, black for ground, and other colors for signals.
     
    Last edited: Jan 12, 2013
    spark8217 likes this.
  3. droggie

    Thread Starter Member

    Oct 21, 2012
    137
    1
    R2 is connected to the green wire to the cap that connects to pin 8. So I'm confused.

    I have posted a pic of the cap. Is it connected correctly now?

    And if I eliminate R3 do I just connect the input with power from the bus?
     
  4. tracecom

    AAC Fanatic!

    Apr 16, 2010
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    No, in the picture, one end of R2 is in a row by itself.

    The new pic of the cap is too big, and I can't scroll it on my laptop. Your other pictures are very good; make this one like you made the other pics.

    No, you don't connect power to the input of the LM386; you connect the output from the MP3 player.

    Study the schematic. Be sure you know which holes on the breadboard are connected to each other.
     
    Last edited: Jan 12, 2013
  5. droggie

    Thread Starter Member

    Oct 21, 2012
    137
    1
    I know the rows connect horizontally and that's what I've done. I've removed R3, connected R2 directly with C2 and R1 with C1 see below.
     
  6. tracecom

    AAC Fanatic!

    Apr 16, 2010
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    I haven't checked it thoroughly, but it looks like C3 is connected to itself; otherwise, it looks better. I have to go out for about 3 hours, but I'll check the thread when I get back.
     
  7. MrChips

    Moderator

    Oct 2, 2009
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    You have the output capacitor at pin-5 shorted to itself and not in series with the loudspeaker.
    Where is your +ve supply voltage connected? This should be on pin-6. You will need a about 10-47μF from pin-6 to GND for power supply filtering.
     
  8. praondevou

    AAC Fanatic!

    Jul 9, 2011
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    C1 and R1 are not connected as shown in your schematic.

    C1 - has to go to ground. Pin 6 of the IC goes to the + pole of C1 and R1.

    (essentially repeating MrChips here)
     
  9. droggie

    Thread Starter Member

    Oct 21, 2012
    137
    1
    So connect the capacitor to the ground bus, connect its positive leave with R1 and the other end of R1 to pin 6?
     
  10. tracecom

    AAC Fanatic!

    Apr 16, 2010
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    Here's a photo.

    [​IMG]

    The negative side of C1 goes to ground. The negative side of C3 connects to the blue wire.

    Notice how I have +V and ground connected to the power rails on both sides of the breadboard. It makes the wiring much simpler.

    Of course you know that you have to connect the ground to both the speaker and the MP3 player.
     
    Last edited: Jan 13, 2013
  11. droggie

    Thread Starter Member

    Oct 21, 2012
    137
    1
    So by keeping both the capacitor's leads in the same rows, I only short them correct?
     
  12. tracecom

    AAC Fanatic!

    Apr 16, 2010
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    Correct. Think about it: if all the pins in a row are connected, then plugging both component leads into the same row connects the leads. That's the whole purpose of having the pins in each row be common.
     
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