INTERCOM

Discussion in 'Electronics Homework Help' started by aadittya123, Nov 6, 2010.

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Nov 6, 2010
Can someone please give a detailed explanation of the working of this 2 way intercom ? The mic for the top speaker is between the 1M and 33 ohm resistors and the mic for the bottom left speaker is at the node just below the top speaker.

2. (*steve*)¡sǝpodᴉʇuɐ ǝɥʇ ɹɐǝɥdModerator

25,412
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Jan 21, 2010
I don't think your explanation and the circuit go together.

AFAICT, the "lower left" speaker is the "microphone" for the "upper right" speaker.

Is this for your homework, or it there some other reason for your question?

6
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Nov 6, 2010
I posted this circuit on several forums and got the same reply. I have no idea how the circuit works. I just posed the question based on a PSpice schematic i found on the net. So the circuit probably is a one-way intercom as you say. Could you please explain how it works? And whats the reason for all the diverse values of resistors and capacitors? And yes, I am working on a mini-project based on this. Its an introductory electronics course, so I don't hv much of a background.

4. (*steve*)¡sǝpodᴉʇuɐ ǝɥʇ ɹɐǝɥdModerator

25,412
2,780
Jan 21, 2010
Why don't you work on something you understand.

There are a diverse range of resistors and capacitors because they are values that will make the circuit work.

You should first see if you can figure out the function of the two 1k resistors. For this purpose you can ignore the 100 ohm resistor.

6
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Nov 6, 2010
voltage divider?

6
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Nov 6, 2010
could you guide me to some reference material that will help me understand this circuit. what should i read up to get a grasp of whats goin on in the circuit?

6
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Nov 6, 2010
how do i simulate it on spice? As in how would i provide input, say for eg a sine wave? and where do i check the output?

8. (*steve*)¡sǝpodᴉʇuɐ ǝɥʇ ɹɐǝɥdModerator

25,412
2,780
Jan 21, 2010
Personally, I think it is a horrible design.

Do some research on op-amps and audio amplifiers. Also try to gain an understanding of why double-ended power supplies are used.

Once you have done that, the operation of this circuit will no longer be a mystery. I'm not sure whether it will help you figure out why it's so bad though.

9. Laplace

1,252
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Apr 4, 2010
In any op amp circuit (that works) you can be sure that the voltage at the (+) input is the same value as the voltage at the (-) input of the op amp. So what is the value of the quiescent collector current flowing through the output speaker? Understanding the quiescent state is your first clue to knowing how the circuit works.

10. (*steve*)¡sǝpodᴉʇuɐ ǝɥʇ ɹɐǝɥdModerator

25,412
2,780
Jan 21, 2010
Heh. Then check to see what quiescent current speaker manufacturers would recommend -- hint, it's a round number.

That's one reason I don't like this circuit.