Discussion in "Project Help" started by    kakshay92    Jul 7, 2012.
Sat Jul 07 2012, 10:04 AM
#1
I am trying to make the "Cellphone operated Land Rover" project given in the EFY magazine, pdf attached.

The H-Bridge IC circuit is working properly and to my knowledge, everything in the MT8870 DTMF Decoder IC circuit is also soldered correctly.

I am using Nokia 2300 for my project and the original earphones that came with it. They work properly when listening to radio, or talking to someone over the phone.

However, the MT8870 IC does not give output when I connect it to my AT89S52 microcontroller. I have written a simple program to transfer everything from port 0 to port 1 (in which an LED board is connected) - so that the corresponding output of the MT8870 (binary) will be shown on the LED board. But it continuously shows 0000, even on pressing keys.

The connector for my phone is of the TRRS type - and my speaker wires have connection to TIP and the second RING.

Please assist me in my project. I am unable to understand where I have gone wrong.
Sat Jul 07 2012, 08:15 PM
#2
first u should get the dtmf o/p ....
in u r case check the crystal ,discreate components especialy capacitor.....
to see the tone is recive see the strobe pin on decoder ic ..when tone recive this pin is hi .....it means tone recived propely

''However, the MT8870 IC does not give output when I connect it to my AT89S52 microcontroller.''
means you get the o/p when micro is removed.....if this is problem see the ground connections of both are connected propely by a continouty test....
Sun Jul 08 2012, 07:19 AM
#3
How do I check the crystal and capacitors?

I will try the strobe pin, thank you for that idea!
Sun Jul 08 2012, 06:15 PM
#4


How do I check the crystal and capacitors?

kakshay92


If you don't have use of an oscilloscope the best way is to replace
the capacitors,then the crystal.

Check your soldering carefully.
Sun Jul 08 2012, 07:13 PM
#5
@ kakshay92
attach circuit according to this schematic

i test it and it is working ok
first u has to be able to get out put of the decoder ic then go to controller that is second step
u can use this software to generate the DTMF tones in the pc or laptop
http://www.polar-electric.com/DTMF/InstallDTMFencoder.exe
use headphone with the laptop and connect it with the circuit
now when laptop generate DTMF tones according to that led showw the status of the ic output
is is an easy and cost free method to check dtmf ic
i use this program is so useful
use stereo connector with laptop to IC connection
 kakshay92 like this.
Mon Jul 09 2012, 04:44 AM
#6
I would be better if you check just the MT8870 receiver part first, remove your microcontroller and see the output of DTMF decoder using multimeter. this will ensure that a part of your circuit is working fine. then you can check controller side if things are going wrong.
Mon Jul 09 2012, 03:35 PM
#7
Thank you everyone for your efforts! I went to my instructor and he suggested a few resistors and capacitor changes, am going to try that and hope it will work!
Mon Jul 09 2012, 05:56 PM
#8
Good Luck kakshay92
 kakshay92 like this.

Get Social

Information

Powered by e107 Forum System

Conversation

Mon Jan 16 2017, 03:15 PM
Rutuja
How can we read notepad file using random acess file
Fri Jan 06 2017, 06:18 AM
muhammad Umar
i need cd4047 library file for protious please help me i s
ExperimenterUK
Wed Jan 04 2017, 09:01 PM
@Emin what is your site user name ?
Tue Jan 03 2017, 11:16 PM
Emin
Emin: I'm already a member since 2012 and entered repeatedly during period. But now it is impossible and obtaining a new registration is also failed. The same error message specifying that two e-mails i entered are different!. In fact thaey are the same. Now, what will be happen, what is your solution? Thanks..
Tue Jan 03 2017, 11:15 PM
Emin
I'm already a member since 2012 and entered repeatedly during period. But now it is impossible and obtaining a new registration is also failed. The same error message specifying that two e-mails i entered are different!. In fact thaey are the same. Now, what will be happen, what is your solution? Thanks..
Sun Jan 01 2017, 03:14 PM
Manoranjana Chary
Write an embedded program of increment and decrement in LCD connected to two keys of int1 and int0. Can u please send me the code for this as fast as possible because i need to submit it in college kindly
ExperimenterUK
Sat Dec 31 2016, 06:28 PM
Happy New Year everyone
ExperimenterUK
Sat Dec 31 2016, 06:27 PM
Please post questions in the forum, the chat box is for chat
Thu Dec 29 2016, 07:47 AM
drashti ranolia
can anyone help me for the microcontroller 8051 programming code for street lights that glow on vehicle movement using IR sensors ?
Tue Dec 27 2016, 11:45 AM
Shubhangi
Do we have to write lookup table for d6t thermal sensor?

Downloads

Comments

sarfrosh92
Sun Jan 15 2017, 09:18 AM
Deepakvaishu
Wed Jan 11 2017, 10:25 AM
rana_jee773
Sat Dec 10 2016, 11:22 AM
[email protected]
Thu Dec 08 2016, 11:02 AM
Jonathan.kei
Mon Nov 21 2016, 04:30 PM
AVRuser1
Sun Nov 20 2016, 06:07 PM
JaguarPaw
Thu Nov 17 2016, 07:44 PM
PeterJohn
Mon Nov 14 2016, 05:54 PM

Online

Guests: 45, Members: 0 ...

most ever online: 182184
(Members: , Guests: 182184) on 06 Aug 2010: 05:37 AM

Members: 37796
Newest member: sarfrosh92
Forum Activity
Deepakvaishu Avatar
Posted By Deepakvaishu
Mon Jan 16 2017, 08:31 AM
you are right ..I should not include '\' at t...
Deepakvaishu Avatar
Posted By Deepakvaishu
Mon Jan 16 2017, 06:07 AM
No ,its not the null character, its just the '...
sankalp_s Avatar
Posted By sankalp_s
Sun Jan 15 2017, 07:55 PM
There is a fault in your Proteus design.If you loo...
sarfrosh92 Avatar
Posted By sarfrosh92
Sun Jan 15 2017, 10:04 AM
The 8051 Microcontroller (3rd Edition) by I. Scott...
ExperimenterUK Avatar
Posted By ExperimenterUK
Sat Jan 14 2017, 11:59 PM
The site editor may have removed the 0 from \0.Actually it should not be needed, sochar *phone_no[3 ]={"1234567890" ," 9087654321" ,"76676667676"}; //array of pointers should work.
ExperimenterUK Avatar
Posted By ExperimenterUK
Sat Jan 14 2017, 11:54 PM
There is a fault in your Proteus design.If you loo...
sankalp_s Avatar
Posted By sankalp_s
Fri Jan 13 2017, 06:52 PM
Hi phill sir.. testButton1: ...
Deepakvaishu Avatar
Posted By Deepakvaishu
Fri Jan 13 2017, 11:58 AM
suppose i have this arraychar *phone_no[3 ]={"1234...
ajay_bhargav Avatar
Posted By ajay_bhargav
Fri Jan 13 2017, 05:59 AM
You need to send AT command one by one to all the ...
Deepakvaishu Avatar
Posted By Deepakvaishu
Wed Jan 11 2017, 10:47 AM
How to send the same message to multiple contacts ...