Telephone auto-dialer

Discussion in 'The Projects Forum' started by steven334, Aug 9, 2011.

  1. steven334

    Thread Starter Member

    Aug 9, 2011
    37
    0
    Telephone auto-dialer ::
    I would very much like some advice on building a programmable Telephone auto-dialer.
    I have 35 momentary (normally open) switches.
    I would like to program different telephone numbers to each switch.
    When a switch is pressed it’s number will be dialed out allowing for a one minute telephone call.
    After one minute it will hang up.
    My budget is about $600 dollars
    (of course I have as telephone line)

    Advice or links to helpful products or components are appreciated.

    Thank you
    Steven
     
  2. THE_RB

    AAC Fanatic!

    Feb 11, 2008
    5,435
    1,305
    You could use a DTMF encoder IC, that makes the "touch tone" sounds, and control it from a microcontroller that would send the correct phone number and also do the 1 minute timing.

    It's also important to use the correct voltage isolation etc connecting to the phone line, and check legalities in your local area too!
     
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  3. steven334

    Thread Starter Member

    Aug 9, 2011
    37
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    Is there a more turn-key solution?

    thanks
     
  4. SgtWookie

    Expert

    Jul 17, 2007
    22,182
    1,728
    Here's a telephone dialer a fellow made using a keypad, a PIC, and an NTE1690 DTMF dialer IC:
    http://avtanski.net/projects/phone_dialer/
    The person who did the project posted a link to that page on our site, and I added some notes about generating DTMF instead of using the NTE1690 on this thread:
    http://forum.allaboutcircuits.com/showthread.php?t=11991
    Or, this code might be merged in with Avtanski's code:
    http://www.piclist.com/techref/microchip/dtmf-de-rb.htm

    You'll probably need the programming capability via a keyboard to enter/change your phone numbers anyway. You might could expand the 1st program to allow storing more numbers (using a more capable microcontroller, of course) - like a PIC16F1527.
    Datasheet link: http://ww1.microchip.com/downloads/en/DeviceDoc/41458B.pdf
    That microcontroller has 55 I/O pins, so you'd have enough to monitor your 35 buttons individually.

    You'd have to write the code to poll/de-bounce those 35 buttons, and add a switch so that you could select whether the keypad or the 35 buttons were to be monitored. You might make the keypad removable.

    You'd also need to add code to time the call. Detecting whether something has picked up on the other end (in order to start the 60-second timer) might be a bit dicey. You might check for the absence of a "ringing" signal or "fast busy" - but those can change depending on the exchange the answering phone is on.
     
  5. THE_RB

    AAC Fanatic!

    Feb 11, 2008
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    A PIC microcontroller can also generate high quality DTMF tones itself, without needing an external IC.

    See this page Tutorial 13;
    http://www.romanblack.com/SG/SG_tutorial.htm#DTMF

    As for your "turn-key solution for under $600" you might want to pay a few hundred to a university student who is good with PICs and they can give you back a completed auto-dialer built to your spec. :)
     
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  6. HarveyH42

    Active Member

    Jul 22, 2007
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    5
    There use to be commercial products out, that dialed numbers through a speaker held to the handset, also had an LCD, and organized you phone/address book, few other functions as well. This was around when pagers just started being the 'status-symbol' device, and before cellphones. Might still be around. There are also programs, maybe free to download, which could be used with a voice modem, and dial a bunch of numbers, and deliver a recorded message for telemarketing. Think what you are looking for, has been done, and gone obsolete. Probably an iphone app, that will do all you want, and more. But if you search around, you might find an old schematic, or a surplus device. You seem a little hesitant about the microcontroller, they really aren't that bad, and pretty easy to get started with. I don't use PIC myself, but it's probably a good choice, since it very popular among hobbyist, and you'll get the most help getting started, and getting your project up and running quickly. Plus, once you get one build and working, it's very simple and cheap, to replicate.
     
  7. steven334

    Thread Starter Member

    Aug 9, 2011
    37
    0
    thanks for the encouragement regarding microcontrolers.
     
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