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need assistance regarding DTMF DECODER in mini project

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Newbie level 3
Jan 7, 2013
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My Project was "cell pone controlled robot without microcontroller'.I have been trying for output since a month.But i couldnot get it.For verifying dtmf decoder output I placed leds at 4 o/p pins but those leds never glown till now.I was unable to know what the problem is?please any one explain me regarding this output checking connections e.t.c.please if possible give me mail id for further mail id is

The above link has the details of my project circuit diagram,components e.t.c.I had connected all the components but got struck at the input to dtmf decoder.I dont have a n idea how to give input to dtmf decoder through ear phones.and to check dtmf decoder binary o/p I placed 4 LEDS at 4 o/p pins but we were unable to get output.

Try connecting a 100 Ohm resistor across the input to ground then wiring it across the earphone output of the phone. The most likely cause of problems is the phone itself, most will not produce any audio unless it sees a low impedance across it's earphone socket, that's what the 100 Ohm resistor emulates. The other thing to watch for is the transmission form the phone itself. If you place it too close to the circuit there's a stong possibility of it's transmiter inducing voltages into the wiring that upset it's operation, keep them at least 0.5m apart.

thamk you for help.I will try this modification monday because I was out of station now and if there arises any issue i will let you know.

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