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dtmf project [help]

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rahuljin

Thu Dec 27 2007, 01:21PM

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hello everyone,

i recently finished my first project (car based on 8052 uC with wired remote).

now i want to make remote wireless and i am thinking about dtmf (not rf). i read about it on net (googled it and read many tuts), but don't get anything !!! i dont know about circuits much !!! so please help me !!!
i also found a good site but not get much !!!
http://www.freewebs.com/maheshwankhede/dtmfdecoder.html

i donot konw how to interface phone with these chips( CM8870 and KT3170) and the circuit diagram is very diffcult to understand !!! i dont know what to do ???

Ajay

Thu Dec 27 2007, 11:35PM

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Please tell me what problem you are facing..
the circuit given in that website is fairly simple. i recommend you to read datasheet of CM8870 will make you clear about the working of IC and interface.

DTMF also need a wired interface.. are you going to use telephone line?

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rahuljin

Fri Dec 28 2007, 12:07AM

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i want to use a nokia mobile phone (1100) !!! but dont know how to connect it with the circuit (receiver side) !!!
i hav to put all the resistors, capacitors and transistor or they are in build ???

my plane is to call the other phone on car through my phone !!! and then operate the car with my phone !!

Ajay

Fri Dec 28 2007, 01:56AM

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oww.. ok.. thats a good idea..
yes you need all resistor caps and crystals..
also you need to make circuit that detect ring and pick the call.. after that directly couple the speaker with CM8870.

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rahuljin

Fri Dec 28 2007, 05:52AM

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so i ahv to open the mobile phone and do the circuit work ???

Ajay

Fri Dec 28 2007, 06:34AM

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no.. make use of headset.. just use the speaker wire..

be smart

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xx1mar

Fri Dec 28 2007, 03:01PM

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I think you are planning to interface your nokia phone with the microcontroller and control it by dtmf. you can use the CM8870 as your dtmf receiver. it is very easy to build.. you can use winbond w91312 as your dtmf tranmitter

Ajay

Fri Dec 28 2007, 11:43PM

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there is no need to transmit DTMF as there nothing on the user side which can understand DTMF. and ofcourse CM8870 is the best choice

for DTMF conversion/reception.

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rahuljin

Thu Jan 17 2008, 05:32AM

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hi can u tell me what is the relay dpot in that circuit and what is the use of that circuit ,and also how can i connect the whole circuit with the headset of the phone as u have mentioned above
do i have to cut the wire of headset and then join it to circuit