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Dialer problem with a picchip

Hello,

I have a recuring problem when connecting my circuit to the phone line. basically the circuit I use is :

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with the exception that I connect B3 to an 8th order low pass filter and the output of that goes to the positive of the transformer. Also I use picbasic to create my DTMF. I connected a small audio speaker to the terminal of the phone line along with the the line itself. The problem is as follows, when the relay is energize, I hear a dial tone ( well thats good) , then I also hear the controller dialing.. both at the same time, so the number is never really dialed, anybody know why?

K
Reply to
lerameur
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What are your audio levels at the line? Tom

Reply to
Tom Biasi

Well, from what you're saying and what I see on that sight, I would say that some how you have hacked it and not removed the actual rotary pulse dialing code out of it?

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Reply to
Jamie

Looks suspiciously like it. At first sight I though he was intentially trying to send dial pulses.

Graham

Reply to
Eeyore

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I am just using the diagram on that web site. That is it, no program no nothing else. Ok that said, I modified the hardware because I am using DTMFout in picbasic that produces the dialing., I just added a max7480 to filter out the noise because the signal get to the audio transformer.

k
Reply to
lerameur

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Meaning ?

K
Reply to
lerameur

:

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If the CO is detecting DTMF, dial tone will stop.

Some POTS lines won't pass DTMF if T/R are reversed. Levels (too high, often) & distortion can hurt DTMF detection. Digit-on or inter- digit time might be too short; send just 1 digit & see if DT stops.

JM

Reply to
John Mianowski

You might want to post your ACTUAL circuit & ACTUAL program, if you want to get ACTUAL good answers. Posting an example of what it ISN'T, isn't necessarily going to get you what you want.

JM

Reply to
John Mianowski

Maybe you're over driving the line?

--
"I\'d rather have a bottle in front of me than a frontal lobotomy"

"Daily Thought:

  SOME PEOPLE ARE LIKE SLINKIES. NOT REALLY GOOD FOR ANYTHING BUT
  THEY BRING A SMILE TO YOUR FACE WHEN PUSHED DOWN THE STAIRS.
http://webpages.charter.net/jamie_5"
Reply to
Jamie

"then I also hear the controller dialing..". From the write up, I thought it -was- designed to pulse dial using the relay. No?

Reply to
john jardine

Try disconnection the audio feed to the xformer from the chip and let it go through the process. See if then, it is causing the problem. If it does not cause the line to reset, then you know you have an over driving issue.

Also, look at the quality of the signal on the line side using a scope.

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Reply to
Jamie

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Ok I will make a schematic. I look in my pspice but I dont have anypic chip or the max7480 IC. Anyone know of a program that contains most of the IC s out there? without being a simulation software.

Reply to
lerameur

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I got the circuit working now, the odd thing it works only when I put the speaker (9 Ohms) on the transformer, The positive on the positive of the dtmf input and the ground on the phone ground. I guess that means it is not getting enough current in.... ?

K
Reply to
lerameur

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here is the diagram. It do not dial without the 9 Ohm resistor...

K
Reply to
lerameur

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Here is the diagram. It do not dial without the 9 Oh

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K

Reply to
lerameur

It's very obvious why it don't work as desired.

You have no DC path on the line side to load it down.. On the C connection, remove the cap and 150 ohm R and connect it directly to the xformer.

Remove the 9 ohm R from where it is and if needed connect it across C and D connections to add a load. I don't know what you're using for a Xformer so I don't know what the DC resistance is in the secondary of it how ever, you need to proper DC resistance to bring the line to a normal off hook voltage.

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"

Reply to
Jamie

1) When capturing a line drawing, DON"T use JPEG.
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*-*-*-*-*-millions-of-colors+*-*-*-small-*-*-*+*-not-suited+*-*-*-*-*-*-*-royalty-*+*-blocks-of-*-color+Use-GIF-*+simple-shapes-*-crisp-edges+*-JPEG-images+not-*-suited-*-*+PNG.format+our+*-replacement-for-*-GIF-*+*-with-text+*-Explorer&strip=1 2) As Jamie noted, you don't even know the difference (electrically) between on-hook and off-hook . Picking up a book on basic telephony and learning the fundamentals would be a good plan. 3) As Mianowski noted, to know what is happing at the other end, you have to be able to *listen* to it. Your regular old transformer won't do that well.
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Again, reading a book on the basics would be useful. Characterizing *what exists* and determining an interface should have come first. Like so many folks, you started at the wrong end of the project (like the guy that wanted to use rechargeable batteries to run LEDs but didn't know what the *energy demand* would be because he hadn't even picked a LED).

Reply to
JeffM

Meaning putting too many volts onto the line. Have you read the specs for DTMF dialling and know the correct levels ? You'll find them on the data sheets for DTMF dialler chips (if you can still find one).

Graham

Reply to
Eeyore

What speaker ? You haven't shown a circuit with a speaker AFAICS.

No it's probably the speaker loading the signal level down to an acceptable level.

From memory you only need about 1 V of signal. You'll probably break the PIC if you use it to drive 9 ohm louspeakers.

You seem to be attempting a challenging project for someone with so little basic knowledge. Like building a house on sand foundations.

Graham

Reply to
Eeyore

Almost certainly your voltage level is wrong initially.

Put a voltage divider between the PIC and the MAX 7480 to reduce the signal level. Try about 20% of the PIC's output.

Graham

Reply to
Eeyore

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