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

Get Social

Information

Powered by e107 Forum System

Conversation

ExperimenterUK
Thu Oct 30 2014, 06:02 PM
This is a chat box..create a thread if you need help...but we don't do homework
Tue Oct 28 2014, 07:33 PM
vinni
hi rickey...anyone got the pgm...pls gimme now
Tue Oct 28 2014, 06:35 PM
potla
hi vinni even i need that program. help me if you get it
Tue Oct 28 2014, 03:22 PM
vinni
1. Using a look-up table in Flash ROM and accumulator offset indexed addressing mode, write a program that acts as a timer. The timer should count from 0 to 59 seconds. After reaching 59, it should go back to 0 on the next second and continue to count up. The timer should use the seven-segment display. The look-up table should contain information on how to display the digits 0 – 9 on the seven-segment display
Tue Oct 28 2014, 03:22 PM
vinni
hello Rickey..i need this pgm very urgently
Tue Oct 28 2014, 01:42 AM
Boy Donald
Dear sir, thanks before. i have some project urgent for my school and my project need this digital countdown timer using 7 segmen display. but your project only show ten minutes countdown, i need your help, can you show me more to change the minute or set the time manually. thank you, sorry for disturbing you.
Tue Oct 28 2014, 01:32 AM
Boy Donald
dear sir
Tue Oct 28 2014, 01:19 AM
Boy Donald
Rickey you inspired me a lot but why i can not change the time ( minute
Sun Oct 26 2014, 02:51 AM
sandeep bankar
dear sir I m facing problem about..how to read number of incoming call in gsm 900 a. pls help how to read it in atmel avr microcontroller.
ajay_bhargav
Mon Oct 20 2014, 11:22 AM
@skrishna, please post in forum so we can help you better.

Downloads

Comments

sanospsa
Fri Oct 31 2014, 09:23 AM
prash5054
Thu Oct 30 2014, 06:34 AM
Max.otto
Mon Oct 27 2014, 01:23 PM
toypoy
Sun Oct 26 2014, 01:06 AM
hiswe
Thu Oct 23 2014, 04:18 PM
pddung93
Sun Oct 19 2014, 01:56 PM
msideal
Thu Oct 16 2014, 08:48 AM
robotgirl
Tue Oct 14 2014, 06:23 PM

Online

Guests: 55, Members: 1 ...
solangi01 viewing search.php

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

Members: 37536
Newest member: sanospsa
Forum Activity
rkodaganur Avatar
Posted By rkodaganur
Fri Oct 31 2014, 01:44 AM
Hi Ajay, I wanted to know can we use transformer ...
Max.otto Avatar
Posted By Max.otto
Thu Oct 30 2014, 11:09 AM
Hello all, before generating i have to give PWM p...
prash5054 Avatar
Posted By prash5054
Thu Oct 30 2014, 06:40 AM
can u post the updated code for the above problem ...
ExperimenterUK Avatar
Posted By ExperimenterUK
Wed Oct 29 2014, 05:36 PM
Thank you for the feedback.It's good to hear when ...
msideal Avatar
Posted By msideal
Tue Oct 28 2014, 05:34 PM
ExperimenterUK: Thankyou so much for helping me......
msideal Avatar
Posted By msideal
Tue Oct 28 2014, 05:18 PM
thanks ExperimenterUK for your help.... I will try...
ExperimenterUK Avatar
Posted By ExperimenterUK
Mon Oct 27 2014, 10:29 PM
Your error seems to be the use of PINC, which is f...
msideal Avatar
Posted By msideal
Mon Oct 27 2014, 05:45 PM
i want to extend my i/o's by writing this code. i ...
Max.otto Avatar
Posted By Max.otto
Mon Oct 27 2014, 01:30 PM
Hi all , i am working with PSoC 5LP. I have contin...
gaurav7577 Avatar
Posted By gaurav7577
Mon Oct 27 2014, 09:53 AM
hello everyone i wanna interface blood pressure se...