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

ExperimenterUK
Thu Apr 28 2016, 01:15 AM
We don't provide project reports. We try to help you do your project
Wed Apr 27 2016, 06:02 PM
abebe tigabu
help me by sending final thesis project automatoc green house effect control by arduino or by at89c51 microcontroller
Mon Apr 25 2016, 03:40 AM
abhinav kumar
Hey there, i want to project report on the RFID BASED SECURITY SYSTEM using AVR microcontroler.please mail as soon as possible. Thank you
Mon Apr 18 2016, 01:07 PM
umesh parekh
i want c code for rfid based car parking system using 8051 and parking slot indicator.if u have please email me
Mon Apr 18 2016, 10:35 AM
Prakash Rao
i need to work on OCR for Numbers, could not find any such projects done using 8051
Wed Apr 13 2016, 07:27 PM
Sanket GUPTA
hey i am new to embedded system and i want to pursue ms in embedded, i have 2 years before i can apply for ms.. in two years can i gain sufficient knowledge. i know c and c++
ExperimenterUK
Wed Apr 13 2016, 05:15 PM
@Suraj.. the method will work ,but edit to suit your compiler
Wed Apr 13 2016, 01:05 AM
Suraj Sridhar
Can I use the LCD Device driver code for STM32F401RET6?
Mon Apr 11 2016, 04:38 PM
Ankith
Can I get the code to access the file from 8051
Mon Apr 11 2016, 04:37 PM
Ankith
can I access a file or folder from sdcard using 8051 microcontroller?

Downloads

Comments

legomaniak
Thu Apr 28 2016, 03:26 PM
APEGEEKZ
Mon Apr 25 2016, 01:54 PM
aishwar
Sun Apr 24 2016, 10:58 AM
nitring
Sun Apr 24 2016, 09:38 AM
Yuri_Golden
Fri Apr 22 2016, 05:15 PM
asif1990
Fri Apr 22 2016, 12:31 AM
Khairnardm
Tue Apr 19 2016, 04:35 AM
amh
Fri Apr 15 2016, 07:45 AM

Online

Guests: 41, Members: 0 ...

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

Members: 37757
Newest member: legomaniak
Forum Activity
legomaniak Avatar
Posted By legomaniak
Thu Apr 28 2016, 03:29 PM
ExperimenterUK Avatar
Posted By ExperimenterUK
Thu Apr 28 2016, 01:12 AM
Did you read / understand my last post to your oth...
APEGEEKZ Avatar
Posted By APEGEEKZ
Mon Apr 25 2016, 02:54 PM
im sending mail using sim900 to gmail but its thro...
ExperimenterUK Avatar
Posted By ExperimenterUK
Sun Apr 24 2016, 06:51 PM
This file was hosted by Rapidshare.comRapidshare.c...
aishwar Avatar
Posted By aishwar
Sun Apr 24 2016, 11:02 AM
ExperimenterUK Avatar
Posted By ExperimenterUK
Fri Apr 22 2016, 07:29 PM
You will have to post your code and Proteus projec...
ExperimenterUK Avatar
Posted By ExperimenterUK
Fri Apr 22 2016, 07:19 PM
If the temperature is below the set point, "if (te...
Yuri_Golden Avatar
Posted By Yuri_Golden
Fri Apr 22 2016, 05:33 PM
Hey Guys, I searched in the forum about a similar ...
Yuri_Golden Avatar
Posted By Yuri_Golden
Fri Apr 22 2016, 05:21 PM
Hey Man, I know that it is been a long time... but...
Karan123 Avatar
Posted By Karan123
Fri Apr 22 2016, 11:39 AM
Hello,Many of Thanks for pseudocontrolcode2.zip ....