i have tried to work with the circuit attached for the basic intercom system but it doesn't run i.e work. i can't dind out where the problem is. please if anyone can help with this.

Attached Images

ckt diagram for simple intercom.gif (45.2 KB, 20 views)

 

Please provide more information.

What do you mean it doesn't work?

Have you check all the connections?

Does it oscillate?

Have you measured the voltages at different parts of the circuit and compared them to what you'd expect?

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Please indicate the way in which you operates the switches for
(a). master to speak and slave to listen
and (b). Slave to speak and master to listen.
I fear that you may not be operating the equipment properly.

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Regards,
Sarma.

 

yes i have checked all the connections and i have done the connections 2 to 3 times. The voltages do not reach to the speakers.

 

Naik, Please see the modified diagram.

I have indicated the changes. It will work.

1. if S1 is pressed (S1a,b&c), Master will speak and slave will listen.

2. If S2 is pressed, Slave will speak and master would listen.

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Regards,
Sarma.

 

Maybe I'm being silly but what does the 8R2 resistor do apart from waste power?

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Screen name: Aloone_Jonez
And http://www.silicontronics.com, same screen name as here.

 

The 8R2 resistor at the output of the LM380 amplifier keeps the circuit from freezing to death.

The one at the input keeps the speaker from resonating too much.

The datasheet for the LM380 shows an RC network to ground that must be used at its output. This circuit doesn't have it.

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Uncle $crooge

 

You mush be being sarcastic.

Shouldn't it form a zobel network?

It should go to 0V via a 100nF capacitor.

__________________
I also post at the following sites:
http://www.stop-microsoft.org http://www.heated-debates.com
Screen name: Aloone_Jonez
And http://www.silicontronics.com, same screen name as here.

 

The circuit shows an 8.2 ohm resistor in series with the output of the LM380 amplifier. It doesn't show Zobel network parts connected correctly.

The output speaker will also resonate a lot the way it is shown. Like a bongo drum.

__________________
Uncle $crooge