Beginner:Two circuits with the same battery. No way.

Discussion in 'The Projects Forum' started by paldep, Mar 6, 2016.

  1. paldep

    Thread Starter Member

    Mar 3, 2016
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    I have an audio amplifier that use 3volt to power on and a preamplifier mic that use 1.5 volt. The preamplifier mic inputs in the amplifier through jack 3.5. When i try to use the same battery source the two circuits power on but it seems that there's inverse current flowing.What can i do? I'am a beginner. :( How can i isolate the two power input from each other ? When i use two different batteries all is going very well. When i Connect the circuits in parallel nothing happens! Thanks
     
  2. blocco a spirale

    AAC Fanatic!

    Jun 18, 2008
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    What do you mean by "inverse current flowing"? A schematic would be useful.
     
  3. Dodgydave

    Distinguished Member

    Jun 22, 2012
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    Wtf#, how can you have inverse current with one battery, post a circuit....
     
  4. paldep

    Thread Starter Member

    Mar 3, 2016
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    Sorry, i'm bad in english. I can post photos of the pcbs front and retro. Can i?
     
  5. nerdegutta

    Moderator

    Dec 15, 2009
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    A close up, in focus, picture of top and bottom.
     
  6. paldep

    Thread Starter Member

    Mar 3, 2016
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  7. ScottWang

    Moderator

    Aug 23, 2012
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    The connection of the Amplifiers and battery should be like this.

    Two circuits with the same battery_paldep_ScottWang.gif
     
    paldep likes this.
  8. paldep

    Thread Starter Member

    Mar 3, 2016
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    thank you Scottwang -i want to connect the circuits with a single battery of 3,7 volt. how to do this?
     
  9. Dodgydave

    Distinguished Member

    Jun 22, 2012
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    You can put a couple of diodes in series with the microphone circuit to drop the voltage down.
     
  10. paldep

    Thread Starter Member

    Mar 3, 2016
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    i have in407 diodes. how to wire them? two diodes to ground(-) and positive?
     
  11. ScottWang

    Moderator

    Aug 23, 2012
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    If the 3.7V is means that the lithium then when it full charge will be up to 4.2V, and its lower voltage is 3.2V, you could adjust the R1 values to match the current you want.

    Two circuits with the same battery_3.7Vbat_paldep_ScottWang.gif
     
  12. paldep

    Thread Starter Member

    Mar 3, 2016
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    i used the circuit posted by Scottwang but the audio from the preamplifier does not pass in the amplifier. If i use separate batteries for each circuits then it work very well. it's very strange
     
  13. ScottWang

    Moderator

    Aug 23, 2012
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    Could you check the ID number of transistors for two amplifiers and labeling them in two parts and their position in the circuit.

    Labeling the bjts from left to right as :
    Preamp : Q1 , Q2, ...
    Audio Amp : Q1, Q2, ...

    Maybe you can draw the output circuit of the preamp and the input circuit of the audio amplifier.
     
  14. paldep

    Thread Starter Member

    Mar 3, 2016
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    F3K2SVFFHWN77C8.LARGE.gif FK0VHVFFHWN77CB.LARGE.jpg spy ear.jpg i made a reserch and found the schematics of my preamplifier. . the amplifier is based on a ka2209 ic. ,four 103k 100 v, one224k 100sg, two 104 cap, a 0.47uf and a 220uf10v and a led for the on off. sorry but i'm a beginner.
     
  15. ScottWang

    Moderator

    Aug 23, 2012
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    If you have the capacitors as 1~10uF/10V~16V then in series with the output - C of Q1(2N2904), put the positive(+) with C of Q1 and the negative to the input of audio amplifier.
     
  16. paldep

    Thread Starter Member

    Mar 3, 2016
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    i will try. Thanks!
     
  17. paldep

    Thread Starter Member

    Mar 3, 2016
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    Tried. Doesn't work. Thanks anyway.
     
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