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 Nov 20 2014, 06:00 PM
@Mehboob.. I don't think you can do that.
Sat Nov 15 2014, 06:41 AM
Mehboob
Pls can you send me code in c of PWM generation using UART/serial port in 8051.
Fri Nov 14 2014, 02:51 PM
mohammad aqil
NEED A BOOK ON MICROPROCESSOR AND INTERFACING BY D.V.HALL. RIGHT NOW, I SHALL BE VERY THANK FULL TO U....
Thu Nov 13 2014, 02:15 PM
m
please code hex project avr blood pressure monitor
Thu Nov 13 2014, 05:56 AM
Lambo
hi mate, whats the ajay-bhargav? tell us more pls
ExperimenterUK
Wed Nov 12 2014, 12:56 AM
@tmtm000.. have you been able to join ?
ExperimenterUK
Wed Nov 12 2014, 12:54 AM
@Alice..become a member,then send a PM to ajay_bhargav the site owner.
Tue Nov 11 2014, 03:58 AM
Abhishek Bansal
Thanks a lot for your informative tutorials!
Mon Nov 10 2014, 09:03 AM
Alice
Hello, This is Alice from a PCB rototype manufacturer. Our company is interested in your website contents, and wonder if we can advertise our company with payment on your website. There are two ways to advertise: first, if we an get a instant quote section on your main site columns; second, whether we can get a advertising section if you have any avaliable one. If any of above ways avaliable, please contact me with your detailed scheme and advertising charge. Thanks. Alice
Sat Nov 08 2014, 11:58 AM
Mohamed_123sd
Signals and Systems, 2nd Edition by Alan V. Oppenheim Alan S.willsky with S.Hamid Nawab?

Downloads

Comments

VikiPeter
Tue Nov 18 2014, 09:13 AM
gentlboy
Sun Nov 16 2014, 11:13 PM
philipeastbourne
Wed Nov 12 2014, 05:32 AM
astra91
Mon Nov 10 2014, 08:11 AM
francise
Thu Nov 06 2014, 02:55 AM
ashbir
Tue Nov 04 2014, 11:13 PM
shruthig
Tue Nov 04 2014, 10:50 AM
sk8boardboy
Mon Nov 03 2014, 11:20 AM

Online

Guests: 43, Members: 0 ...

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

Members: 37547
Newest member: VikiPeter
Forum Activity
ExperimenterUK Avatar
Posted By ExperimenterUK
Sat Nov 22 2014, 06:15 AM
@ExperimenterUKI make small table to observe Outpu...
Max.otto Avatar
Posted By Max.otto
Fri Nov 21 2014, 02:31 PM
@ExperimeterUKForgot my last question.As i told be...
Max.otto Avatar
Posted By Max.otto
Fri Nov 21 2014, 02:05 PM
@ExperimenterUKI make small table to observe Outpu...
Max.otto Avatar
Posted By Max.otto
Fri Nov 21 2014, 01:12 PM
@ExperimenterUKThank u. I do it. Ohne Period it's ...
ExperimenterUK Avatar
Posted By ExperimenterUK
Thu Nov 20 2014, 05:56 PM
You set the on/off times here as 47%float PWMcom...
vijay.parmar1992 Avatar
Posted By vijay.parmar1992
Thu Nov 20 2014, 04:06 AM
Right now i am studying Bootloader.I want to writ...
Max.otto Avatar
Posted By Max.otto
Wed Nov 19 2014, 03:11 PM
How can i get PWM on-off time..?pls check the atta...
Max.otto Avatar
Posted By Max.otto
Wed Nov 19 2014, 03:05 PM
I am using PSoC 5LP.pls check the attached design ...
ankitbajaj01 Avatar
Posted By ankitbajaj01
Wed Nov 19 2014, 01:49 PM
Thanks for the prompt response, I will try it out ...
engr1931 Avatar
Posted By engr1931
Wed Nov 19 2014, 11:45 AM
this one sir! i attached the whole project! ...