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Michelle O'Brien Monday, November 20, 2017 by Michelle O'Brien

Rotary dials off old phones

Clive Maxfield in his Max's Hot Beans column in November's EPE magazine had en excellent item about rotary dials off old phones, specifically in Max's case the U.S .Western Electric #7 dial for 500 series telephones., and some of the uses to which they can be put - for example, used in conjunction with an Arduino.


Max told where you can get a Western Electric dial in the US - the Old Phone Shop - and promised after experiment with the Western Electric dial he bought from them that he will report in future Hot Beans columns in EPE on different ways he has found for entering and displaying data.


The restored Western Electric dials are first class. But It struck me that with a bit of know-how rotary dials off old British Telecom phones (and maybe even push-button dials off old BT phones - of which I have a drawful)  might equally well be adapted to the same purpose.

So this is to ask if anyone has any examples of doing this that they can share here..

A combination of old phone dial, an Arduino (with delay coding to eliminate contact bounce?) and shift registers and/or counter chips was a combination that immediately sprang to my mind  although I haven't yet experimented.

Michelle O'Brien





Comments

  • by  David Ashton (edited)
    Michelle... British Phone Dials are (for once) more or less the same as US ones, Google "Pulse dialling" for more info.  Basically 10 pulses per second with a 66% break ratio.

    You could just use a 555 as a debouncer (trigger the 555 with the contact and have it supply a 50 ms Pulse) and then feed it to a 4017 or other counter, if necessary with a decoder and display to show you what you dialled.  You can count on about a 300 ms minimium pause between digits (the dial contacts will stay closed during this time).  But if you're feeding into an Arduino, all the debouncing and storage of the digits can be done in software, and you can then do what you want with the data - display it, use it to arm or disarm things, etc.

    Push-button dials...the early pushbutton phones could be switched between pulse and tone dialling (the REALLY early ones just did pulse) but depending how much you strip them down you might end up with just a matrix keypad that drives an IC in the phone.  There are ICs you use to decode keypads,

    If you can get the tone dialling to work there are ICs you can use to decode the tones  to (usually) a BCD output - the CM8870 is a common one (sometimes with different prefix letters).  You can feed the BCD into an Arduino as above and do what you want with it.

    If you want any more details on any of the above let me know - I'm not sure if I answered your question?

    Cheers / David

    PS.  I wonder why Max has Hot Beans in EPE in the UK and Cool Beans on EEWeb in the states.....

    PPS.  Did you ever manage to get Radio France?


  • by  Elizabeth Simon

    Since many Amateur radio repeaters use tones sent over the air to control functions. I suspect that a search will give you a number of project examples.  I helped design a couple repeater controllers. The first used a CM8870 type of decoder into an Atmel AVR (same chip as Arduino). The second version used an ARM processor and a Goertzel algorithm to decode the tones. See the following for an explanation of Goertzel

    https://courses.cs.washington.edu/courses/cse466/12au/calendar/Goertzel-EETimes.pdf

    Elizabeth


    PS:  David, in response to you inquiry as to the reason for the difference in the names of Max's columns. I suspect that this may be related to the relative temperatures of his residence locations.

    • by  David Ashton
      @Elizabeth...cool beans in Alabama, hot beans in Sheffield... so it think that should be "INVERSELY related to the temperatures :-)
  • by  David Ashton
    @Elizabeth...cool beans in Alabama, hot beans in Sheffield... so it think that should be "INVERSELY related to the temperatures :-)
  • by  Alan Winstanley

    @ David @ Elizabeth   Actually Max's column titles alternate each month! Cool Beans this month (December issue, out now), Hot Beans last month.

    Alan

    • by  Aubrey Kagan

      Alan


      Actually Max's column titles alternate each month!

      Does Max know about this, given the origin of the title?

      Might I suggest that since "Cool " is not the direct opposite of "Hot " that you add other alternatives such as "Cold Beans" and "Warm Beans"!

      • by  David Ashton
        You could expand on this.... broad beans... runner beans.... canellini beans.... baked beans ... 

        I always thought Max was half-baked.......  :-)

  • by  Aubrey Kagan

    Alan


    Actually Max's column titles alternate each month!

    Does Max know about this, given the origin of the title?

    Might I suggest that since "Cool " is not the direct opposite of "Hot " that you add other alternatives such as "Cold Beans" and "Warm Beans"!

    • by  David Ashton
      You could expand on this.... broad beans... runner beans.... canellini beans.... baked beans ... 

      I always thought Max was half-baked.......  :-)

  • by  David Ashton
    You could expand on this.... broad beans... runner beans.... canellini beans.... baked beans ... 

    I always thought Max was half-baked.......  :-)

  • by  Rick Curl
    I've got some pinball machine scoreboard reels, which are in some ways similar to stepping relays. I'll bet they could easily be driven by the pulses from a telephone dial. 

    I've been meaning to ship them up to Max to see what kind of crazy creation he puts them in.

    -Rick

     

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