Hello Trax,
I have been trying the phone line controller V1 by redesigning it for a single sided pcb using proteus software. Unfortunately I don't even get the LED come on. It only came on once but very slowly and only to a dim light. I have checked the crystal's output using a oscilloscope. The output is a nice sine wave of about .6v PTP. Also when ringing, the output at the pin 5 of the opto goes low to about zero volts in the shape of a square wave. So pin 7 of the pic does go down alternately but nothing else happens. The pic was programmed using the supplied hex file.
I did change the zeners to 50v but since there was no improvement I changed back to 75v. I also started by using a 100k resistor at the input to pin 2 of the 8870 and reduced it incrementally to 15k at the moment but still no change is obsereved. The voltage at pins 2 & 3 of 8870 seems to be 1v DC all the time regardles of ringing or not. It would be very nice of you to give me some help and especially explain the part of the circuit at the input to pins 2 & 3 including the transformer and the 4148 diodes and the 10uF capacitor etc explaining how these are supposed to function. I only do electronics as a hobby so my theoretical base is not very strong.
Thanks a lot and hope to hear from you soon.
Cheers
Bluebird
phone line controller v1
Moderators: pedja089, stojke369, [eDo], trax
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Bluebirdiran
- Posts: 14
- Joined: 20-04-2010, 07:29
Re: phone line controller v1
Hello again,
I wish I could take back most of what I had said in the above post. The uController had not been programmed properly. I have just progrmmed it again, the LED blinks ok and the relay latches after the first or second ring but no beeps are heard for password entry. After the phone is on hook, it seems to release the relay and the line after a few seconds.
So pls. tell me where I am going wrong now.
Thanks
Bluebird
I wish I could take back most of what I had said in the above post. The uController had not been programmed properly. I have just progrmmed it again, the LED blinks ok and the relay latches after the first or second ring but no beeps are heard for password entry. After the phone is on hook, it seems to release the relay and the line after a few seconds.
So pls. tell me where I am going wrong now.
Thanks
Bluebird
Re: phone line controller v1
I was just about to say that you didn't program the PIC properly 
Re-check the part of the circuit on pin PORTB.3 of PIC. That's where it sends the "beep" signals to the phone line. The resistor "10k-100k might need adjustment" is only if your MT8870 is not accepting DTMF codes, but you didn't get to that part yet, so don't worry about that resistor.
I think that your problem is in the "600ohm transformer". Try replacing it with another one and also replace those two 1N4148 diodes at the secondary of the transformer. They are limiting the audio voltage to +/-0.7V max. Your "hook" relay also might not work properly even though it clicks.
Re-check the part of the circuit on pin PORTB.3 of PIC. That's where it sends the "beep" signals to the phone line. The resistor "10k-100k might need adjustment" is only if your MT8870 is not accepting DTMF codes, but you didn't get to that part yet, so don't worry about that resistor.
I think that your problem is in the "600ohm transformer". Try replacing it with another one and also replace those two 1N4148 diodes at the secondary of the transformer. They are limiting the audio voltage to +/-0.7V max. Your "hook" relay also might not work properly even though it clicks.
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Bluebirdiran
- Posts: 14
- Joined: 20-04-2010, 07:29
Re: phone line controller v1
Hello Trax
Thanks a lot for your help. Using an oscilloscope I have checked the output from pin B3 of the pic at the moment of the ralay klicking, and it does send out some sort of a wave similar to a square shape for a very short time. I presume this must be the beep. Then I checked the two 4148 diodes and they seem to be ok. What I did next was to put two of each (4148 didodes) in series so that I get a bigger voltage at the transformer. The voltage did show a kind of a higher magnitude, though observing it is very difficult. But still no beep.
Then I checked the transformer and it seems to be ok though I did not change it. It shows about 580ohm either side as it is "in circuit". The relay was also thoroughly checked and there is no problem with that either. It does short the path. I have also taken out theVDR.
On the telephone line coming from outside I get a very noisy wave when on-hook. They cannot be anything else but noise I would presume. But when the relay latches going off-hook, I get much more orderly waves which also seem like noise but with very much smaller amplitudes and more orderly. I would assume this must be the transformer feeding back ...OR I may be totally wrong.
Thanks for your help and I would appreciate your further guidance in this regard.
Thanks a lot
Bluebird
Thanks a lot for your help. Using an oscilloscope I have checked the output from pin B3 of the pic at the moment of the ralay klicking, and it does send out some sort of a wave similar to a square shape for a very short time. I presume this must be the beep. Then I checked the two 4148 diodes and they seem to be ok. What I did next was to put two of each (4148 didodes) in series so that I get a bigger voltage at the transformer. The voltage did show a kind of a higher magnitude, though observing it is very difficult. But still no beep.
Then I checked the transformer and it seems to be ok though I did not change it. It shows about 580ohm either side as it is "in circuit". The relay was also thoroughly checked and there is no problem with that either. It does short the path. I have also taken out theVDR.
On the telephone line coming from outside I get a very noisy wave when on-hook. They cannot be anything else but noise I would presume. But when the relay latches going off-hook, I get much more orderly waves which also seem like noise but with very much smaller amplitudes and more orderly. I would assume this must be the transformer feeding back ...OR I may be totally wrong.
Thanks for your help and I would appreciate your further guidance in this regard.
Thanks a lot
Bluebird
Re: phone line controller v1
Hi,
Just a simple test: When you short the hook-switch, you should hear a dial-tone at the earphones. If not, you've got the problem with some of those components.
Just a simple test: When you short the hook-switch, you should hear a dial-tone at the earphones. If not, you've got the problem with some of those components.
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Bluebirdiran
- Posts: 14
- Joined: 20-04-2010, 07:29
Re: phone line controller v1
Hi Trax
I did the audio test. I could hear the dial tone from the transformer side of the .1uF polyester cap. but not after it(towards the 8870). I used an 8 ohm 0.5W speaker for the test. The dial tone was quite faint. I also used a earphone and then could hear the tone a bit louder. So I changed the polyester cap. with a 104 ceramic disc and the same thing happened. I don't think that both the caps can be faulty, do you? The sound just doesn't seem to get through the cap.
Any other suggestions pls.
Thanks
Bluebird
I did the audio test. I could hear the dial tone from the transformer side of the .1uF polyester cap. but not after it(towards the 8870). I used an 8 ohm 0.5W speaker for the test. The dial tone was quite faint. I also used a earphone and then could hear the tone a bit louder. So I changed the polyester cap. with a 104 ceramic disc and the same thing happened. I don't think that both the caps can be faulty, do you? The sound just doesn't seem to get through the cap.
Any other suggestions pls.
Thanks
Bluebird
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Bluebirdiran
- Posts: 14
- Joined: 20-04-2010, 07:29
Re: phone line controller v1
I have tried a third 104 ceramic disc cap. still the same. Sound does not seem to get through.
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Bluebirdiran
- Posts: 14
- Joined: 20-04-2010, 07:29
Re: phone line controller v1
Hi agin
I forgot to ask you about the choice of oscillator option in the software when programming the PIC. Which of the 4 options do you recommend or does it not matter. I had chosen XT.
Thanks
Bluebird
I forgot to ask you about the choice of oscillator option in the software when programming the PIC. Which of the 4 options do you recommend or does it not matter. I had chosen XT.
Thanks
Bluebird
Re: phone line controller v1
Yes, you must use XT option, and I also select: Brown-Out-Detect enabled, Code-Protect = not important, Power-Up-Timer enabled, MCLR enabled.
Try removing two 1N4148 diodes at the secondary of the audio transformer and see if it will amplify (this is just for testing!).
Maybe your transformer is not 1:1 so the signal gets very weak after the transformer? You should take one out from an old PC modem, that usually works. That way you can also see the circuit in the modem itself - it is 90% the same as mine.
By the way, on the left side - the resistor is 560 ohms, not kOhms
Try removing two 1N4148 diodes at the secondary of the audio transformer and see if it will amplify (this is just for testing!).
Maybe your transformer is not 1:1 so the signal gets very weak after the transformer? You should take one out from an old PC modem, that usually works. That way you can also see the circuit in the modem itself - it is 90% the same as mine.
By the way, on the left side - the resistor is 560 ohms, not kOhms
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Bluebirdiran
- Posts: 14
- Joined: 20-04-2010, 07:29
Re: phone line controller v1
Hi Trax,
I have removed the two 4148's but no improvement.
The transformer I am using is exactly the same as the one Masoud used earlier in the V2 of this project. Nevertheless I changed it with another one of exactly the same, but this time I don't even get the line to go off-hook after the number is dialed. It keeps on ringing. It is 1:1, as the ohm of both windings is the same and 600 ohm each.
I have an old modem which is in front of me and it has a transformer which I have taken out and measured. One of its windings is 100ohm and the other one is 130ohm. Should I try this one?
By the way I can hear the beep sent out by the PIC using a headphone right up to the input of the transformer but not at the other side. It seems to be week.
Waiting for your instructions,
Thanks
Bluebird
I have removed the two 4148's but no improvement.
The transformer I am using is exactly the same as the one Masoud used earlier in the V2 of this project. Nevertheless I changed it with another one of exactly the same, but this time I don't even get the line to go off-hook after the number is dialed. It keeps on ringing. It is 1:1, as the ohm of both windings is the same and 600 ohm each.
I have an old modem which is in front of me and it has a transformer which I have taken out and measured. One of its windings is 100ohm and the other one is 130ohm. Should I try this one?
By the way I can hear the beep sent out by the PIC using a headphone right up to the input of the transformer but not at the other side. It seems to be week.
Waiting for your instructions,
Thanks
Bluebird
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Bluebirdiran
- Posts: 14
- Joined: 20-04-2010, 07:29
Re: phone line controller v1
Hi Trax,
I tried the transformer taken out of the modem board anyway, still no good. I had forgotten to put back the 4148's that you earlier said to take out and for this reason was not getting the off-hook state. That is ok now but still no beep.
Waiting,
Bluebird
I tried the transformer taken out of the modem board anyway, still no good. I had forgotten to put back the 4148's that you earlier said to take out and for this reason was not getting the off-hook state. That is ok now but still no beep.
Waiting,
Bluebird
Re: phone line controller v1
Are you sure you connected the transformer properly?
It will not go off-hook if you rotated the transformer by 90 degrees, if you know what I mean.
If you don't know what's wrong, than you must start replacing all parts, one by one until you get it to work! I bet it is the relay that has some crazy resistance at it's contacts. I don't know what else to tell you.
It will not go off-hook if you rotated the transformer by 90 degrees, if you know what I mean.
If you don't know what's wrong, than you must start replacing all parts, one by one until you get it to work! I bet it is the relay that has some crazy resistance at it's contacts. I don't know what else to tell you.
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Bluebirdiran
- Posts: 14
- Joined: 20-04-2010, 07:29
Re: phone line controller v1
Hi Trax,
Yes, the transformer is connected the right way. As I said in may last post, the line goes off-hook now but there is no beep!! This must be the most sought after beep for a long time
Anyway thanks a lot for all your help. I want you to know how much I have appreciated your support. In the mean time if you come up with something new regarding this problem pls. let me know.
Thanks a million
Bluebird
Yes, the transformer is connected the right way. As I said in may last post, the line goes off-hook now but there is no beep!! This must be the most sought after beep for a long time
Anyway thanks a lot for all your help. I want you to know how much I have appreciated your support. In the mean time if you come up with something new regarding this problem pls. let me know.
Thanks a million
Bluebird
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Bluebirdiran
- Posts: 14
- Joined: 20-04-2010, 07:29
Re: phone line controller v1
Hi again Trax
Out of desperation I checked the PIC IC on the programmer and I realized that it cannot verify the content. I reprogrammed it, it give the ok message that the programming and verification is ok. But just to be sure I tried to verify the content again but it give out the same error message as before. Is there something wrong with the code? Do you have a more certain version that you could send me. Maybe all the problems along the way are due to this. This may be like clatching a straw when drowning, but it may be worth a try.
Thanks alot
Bluebird
PS. I tried another hex file just to make sure that there is nothing wrong with the programmer and it verified the content, no problem. So the problem may lie with the code.
Out of desperation I checked the PIC IC on the programmer and I realized that it cannot verify the content. I reprogrammed it, it give the ok message that the programming and verification is ok. But just to be sure I tried to verify the content again but it give out the same error message as before. Is there something wrong with the code? Do you have a more certain version that you could send me. Maybe all the problems along the way are due to this. This may be like clatching a straw when drowning, but it may be worth a try.
Thanks alot
Bluebird
PS. I tried another hex file just to make sure that there is nothing wrong with the programmer and it verified the content, no problem. So the problem may lie with the code.
Re: phone line controller v1
Hi,
During programming (just before clicking the BURN button) unclick the CP (code protect) check box and you will be able to verify it.
Anyway, that is not the problem you are having.
Trax
During programming (just before clicking the BURN button) unclick the CP (code protect) check box and you will be able to verify it.
Anyway, that is not the problem you are having.
Trax
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Bluebirdiran
- Posts: 14
- Joined: 20-04-2010, 07:29
Re: phone line controller v1
Hi Trax
At long last I have managed to hear the life giving beep.
But I don't hear anything after that. After entering the password I don't hear that 2 or 3 beeps that I am supposed to hear. Can you help pls.
Cheers
Bluebird
At long last I have managed to hear the life giving beep.
But I don't hear anything after that. After entering the password I don't hear that 2 or 3 beeps that I am supposed to hear. Can you help pls.Cheers
Bluebird
Re: phone line controller v1
Great news!
Now you need to adjust that resistor that has label "might need adjustment" or something. Lower it until MT8870 starts receiving DTMF signals. You will know that once the LED starts to blink when you send DTMF tones when entering the password.
Now you need to adjust that resistor that has label "might need adjustment" or something. Lower it until MT8870 starts receiving DTMF signals. You will know that once the LED starts to blink when you send DTMF tones when entering the password.
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Bluebirdiran
- Posts: 14
- Joined: 20-04-2010, 07:29
Re: phone line controller v1
Hi Trax
Thanks for your prompt reply. I reduced the resistor to 10K and it works now. But most of the time it does not give me enough time to enter the password. It beeps after the entry of the second digit.
Any suggestions
Thanks
Bluebird
Thanks for your prompt reply. I reduced the resistor to 10K and it works now. But most of the time it does not give me enough time to enter the password. It beeps after the entry of the second digit.
Any suggestions
Thanks
Bluebird
Re: phone line controller v1
That shouldn't happen. Maybe the resistor value is still a bit off and it is receiving a wrong code. Or you are entering a wrong code?
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Bluebirdiran
- Posts: 14
- Joined: 20-04-2010, 07:29
Re: phone line controller v1
I have lowered it to 6.8K and it seems to be ok. Can you give me a clear routine as how to do the setup. I am a bit confused. Thanks a lot
Bluebird
Bluebird