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

ajay_bhargav
Fri Dec 12 2014, 04:38 AM
@Abdul BAsit, Post in forum please. We will help you.
Wed Dec 10 2014, 06:41 PM
Abdul BAsit
I am working on smoke detector using AT89S52 and dont know how its wors..kindly send me circuit diagram and code for its hardware & software implementation
Tue Dec 09 2014, 11:30 AM
Irinel
Please send me the content of that cd-rom (embedded c - michael j pont. Thank you.
Tue Dec 09 2014, 02:45 AM
kmyo
please give me the operation of 12v trickle charger
Sun Dec 07 2014, 07:50 AM
hidawi
we need the circuit diagrom of the remote control of iduction motor by android appliction
PsySc0rpi0n
Tue Dec 02 2014, 10:30 AM
I have no idea... I'm new to micro controllers
Tue Dec 02 2014, 08:35 AM
samarnath dev
how can usb key bord interfasing to dot matrx led moving, by asm51 ?
Tue Dec 02 2014, 08:32 AM
samarnath dev
how can usb key bord interfasing to 8051 by asm code?
Fri Nov 28 2014, 06:31 AM
babar
aoa ,, i need a project for 8051 microcontroler can some one plz give me the pdf form of this project android control robot
Fri Nov 28 2014, 06:30 AM
babar
hi

Downloads

Comments

naimish324
Wed Dec 17 2014, 04:48 AM
sathish177
Tue Dec 16 2014, 06:43 PM
djnokey
Sat Dec 13 2014, 12:12 PM
sai9113
Tue Dec 09 2014, 07:23 AM
alexlomol
Fri Dec 05 2014, 12:06 AM
chandujonty
Thu Dec 04 2014, 10:11 AM
fantasy1214
Mon Dec 01 2014, 01:45 PM
vumbelino
Sat Nov 29 2014, 04:43 PM

Online

Guests: 53, Members: 0 ...

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

Members: 37560
Newest member: naimish324
Forum Activity
sankalp_s Avatar
Posted By sankalp_s
Mon Dec 22 2014, 04:52 PM
Thanks a lot sir, its working, great support, sank...
ajay_bhargav Avatar
Posted By ajay_bhargav
Mon Dec 22 2014, 04:59 AM
Take a look at Serial Communication Tutorial to ge...
ajay_bhargav Avatar
Posted By ajay_bhargav
Mon Dec 22 2014, 04:44 AM
Here is a ready test project by Martin Thomas usin...
ExperimenterUK Avatar
Posted By ExperimenterUK
Sun Dec 21 2014, 10:16 PM
Thanks a lot sir, its working, great support, sank...
hsnjamal Avatar
Posted By hsnjamal
Sun Dec 21 2014, 02:03 PM
First you will need to let us know what IDE you pl...
sankalp_s Avatar
Posted By sankalp_s
Sat Dec 20 2014, 05:31 PM
For what you want,it is easier to not use interrup...
ExperimenterUK Avatar
Posted By ExperimenterUK
Fri Dec 19 2014, 09:58 PM
For what you want,it is easier to not use interrup...
sankalp_s Avatar
Posted By sankalp_s
Fri Dec 19 2014, 06:04 PM
This version works.Edit it to use either method. ...
muhibraza Avatar
Posted By muhibraza
Fri Dec 19 2014, 08:05 AM
software_developer Avatar
Posted By software_developer
Fri Dec 19 2014, 04:54 AM
Which files i have to use?Please give me .zip fold...