problem with dtmf decoder ht9170b

[zouzanda]

i have a problem with my circuit and i can't figure out what.
if i use a parallel phone line it works great but when i call from a cellphone or another phone it doesnt work what could be the problem plz i need an answer as fast as possible if someone knows thanx in advance

 

[sudan]

HI,

Based on your diagram only dedicated link phone only work. Because you are giving the output there. But in the case of Mobile phones, from where you will get the output signal at the time of dialing ?. It is possible too........

It may wrongly identify for you.

Sudan

 

[zouzanda]

dear sir
now ur not right even a cell phone works im sure of that cz it worked 1 time in my case but its not anymore probably a noise problem but i can't figure out a solution
and more explanation is that the phone line is connected to the input when u dial the number a relay with a resistor will open the will so then u can click a number on the cell to be detected with this circuit

 

[sudan]

Hi,


First time it worked. Do one thing... Connect the telephone with your circuit, now it will work perfectly. right ?? Take a CRO (It is best because we can visually see the output) and check the output stage by stage and note down the output.

Now you can connect your cell and do the same process. If any abnormalities are present based on that you can add other circuits.....


Sudan

 

[zouzanda]

thanx man for ur reply but i dont have a SRO and if u mean by that an oscilloscope.i need someone who tried it from before .maybe her faced the same problem. i think while using a cell phone the signal it transmited but its weak because when i raise the telephone i can hear the keys pressed.anyways im confused i've been trying stuff for like 2 weeks and nohting is working :S

 

[cabir]

thanx man for ur reply but i dont have a SRO and if u mean by that an oscilloscope.i need someone who tried it from before .maybe her faced the same problem. i think while using a cell phone the signal it transmited but its weak because when i raise the telephone i can hear the keys pressed.anyways im confused i've been trying stuff for like 2 weeks and nohting is working :S

Hi all
I tried the same schematic
It works fine with all operators
You may try another transformer lets say not 1 to 1 as in your schematic, it can be an impedance transformer 1 to 2,3,4. Ferit cores are much better . Also you try to reduce the resistor 100 K.

 

[zouzanda]

which resistor there r 2 100k the 1st one u mean and by how much should i reduce it is there a limit cz i think its the gain of the amplifier

Added after 33 minutes:

man u r a life savior thank u a lot the solution is i changed the 100k res to a 100k pot and i added a 0.001 cap on the output of the transformer problem solved