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InterCom / Door Phone

Discussion in 'Electronic Projects Design/Ideas/Reviews' started by Non89, Nov 11, 2010.

  1. audioguru

    audioguru Well-Known Member Most Helpful Member

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    Don't you see that your new schematic has no input signal and has the 12V battery connected to the wrong location?
    You also have R5 shorted.
     
  2. 4pyros

    4pyros Well-Known Member Most Helpful Member

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    You are feeding it DC try AC to sim it.
     
    Last edited: Mar 1, 2011
  3. audioguru

    audioguru Well-Known Member Most Helpful Member

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    Your English is bad.

    His 12V battery is in the wrong location and the circuit has no input signal so it has no output signal. Even the DC output voltage is wrong.
    Also R5 is shorted.
     
  4. dave

    Dave New Member

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  5. 4pyros

    4pyros Well-Known Member Most Helpful Member

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    Thanks for pointing that out
     
  6. Non89

    Non89 Member

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    oic, thank .... i want to ask , can i try the master circuit and slave circuit respectively by meansure the output voltage signal from speaker, without connecting both togather?
     
  7. audioguru

    audioguru Well-Known Member Most Helpful Member

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    When you adjust the trimpots to null the local signal then there will be nearly nothing coming from your speaker when you speak into your microphone. The sound comes out of the distant speaker. That is how it avoids acoustical feedback howling where the mic hears the speaker and causes the sound to go around and around making feedback howling.
     
  8. Non89

    Non89 Member

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    i was try the master circuit , measuring those part with Gnd, and the voltage i measured as list, i dunno why the base of transistor input so high , and the mike seem not worked....

    and when i measure output 5 & 8 from the TDA7052a, the circuit became short circuit.... zero voltage measured....
     

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  9. Boncuk

    Boncuk New Member

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    So why don't you measure at the slave circuit?

    the circuit has been explained over and over several times.

    You seem to have the wrong profession or the wrong hobby - possibly both.

    Boncuk
     
    Last edited: Mar 3, 2011
  10. Non89

    Non89 Member

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    the problem is while i connecting speaker, the circuit became shorted, slave and master circuit also same.
     
  11. audioguru

    audioguru Well-Known Member Most Helpful Member

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    Your transistor voltages are completely wrong.
    Boncuk and you are using the wrong amplifier IC:
     

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  12. Non89

    Non89 Member

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    ya , i know ... the base should be response only while i talking ... but i dunno why it maintain 6v++ and mike wasn't work
     
  13. Non89

    Non89 Member

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    so i should change back to TDA7052 ?
     
  14. Boncuk

    Boncuk New Member

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    I don't really see the reason why you pointed out the input coupling capacitor. The circuit contains it!

    (C3 and C4).
     
    Last edited: Mar 3, 2011
  15. audioguru

    audioguru Well-Known Member Most Helpful Member

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    The DC voltage at the base should be +6.0V, not +6.8V.
    The voltage at the emitter should be about +5.3V, not +9.5V.
    The voltage at the collector should be about +10.3V, not +6.0V.
    Ground should be 0V, not +1.14V.
    R7 should be 0V, not +0.6V.
    Both outputs of the TDA7052 should be the same, probably +6.0V, not +1.0V and +10.6V.

    The original circuit and Boncuk's circuit show the polarity of both C4 capacitors backwards.
     
  16. audioguru

    audioguru Well-Known Member Most Helpful Member

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    I showed the original circuit's TDA7052 datasheet that has its pin 2 input grounded with a resistor. I also showed your circuit's TDA7052A with its pin 2 input grounded through the volume control but the datasheet shows a coupling capacitor maybe because it has DC on it. Maybe that is why the DC at the output of the TDA7052A is wrong.
     
  17. Non89

    Non89 Member

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    the input to pin 2 of ic is +1.14V,
    pin 2 of R7 should be 0V, not +0.6V.

    and the speaker output not fixed at +1.0V and +10.6V, while i adjust the P1 , the value will different , either p1 max or min , voltage only +6V same

    i will try TDA7052 IC at monday, see whether i connected speaker will get shorted circuit or not
     
  18. Boncuk

    Boncuk New Member

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    May be wrong or not.

    Comparing the data sheets of the TDA7052 and TDA7052A the only difference is the unconnected pin4 (DC volume control) in the TDA7052.

    The internal connections should be same on both types.

    Reducing the AF-input signal at pin 3 shouldn't have the effect of no speaker output.

    I admit I didn't pay attention to the suffix "A", when I redesigned the circuit.
     
  19. audioguru

    audioguru Well-Known Member Most Helpful Member

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    The datasheet for the TDA7052A does not have enough details and not enough spec's to show why its circuit uses an input coupling capacitor but the TDA7052 does not show an input coupling capacitor.

    Maybe the input of the TDA7052A has a bias voltage that must be kept so it needs an input coupling capacitor. Then when the input is wrongly connected to ground through a resistor it might cause the outputs to have severe offset voltages. I don't use the lousy old TDA7052A because its datasheet is missing so many details. Instead I would use a TDA2822M amplifier in this circuit.
     
  20. Non89

    Non89 Member

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  21. audioguru

    audioguru Well-Known Member Most Helpful Member

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    I think the TDA7052A will work properly if you add the 0.47uF input capacitor that is shown on its datasheet. Don't forget to correct the polarity of both C4 capacitors.

    You do not use the stereo amplifier in figure 17 of the TDA2822M datasheet. You use the mono bridged amplifier circuit in figure 2 and its pcb design in figure 4.
     

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