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Using an old rotary dial phone as your numeric keypad. Just numbers, no operators.

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rotary-numpad

Using an old rotary dial phone as a numeric keypad. No operators though, just the numbers.

See it working on YouTube

Uses

  • An Arduino Micro compatibe board. I used one from KeeYes with ATmega32U4. The microcontroller type in bold is important, if you want to use it in USB mode, hooked to a computer.
  • The Arduino IDE and this piece of code

About the rotary dial

I bought a phone on a local site for classifieds. The dial is a separate unit inside the phone with 3 wires. One is common (in my case it's the white one), the other two are the terminals for two switches.

One switch (on the green wire) is off by default, goes from off to on when you move the dial wheel. Also stays on until the wheel rotates back to the normal position.

The other switch (brown wire) is on by default. Stays on while you rotate the wheel clockwise, but breaks the curcuit once for each number as it's spinning back to the normal position counter-clockwise. 3 breaks = the number 3. 9 breaks = the number 9. 10 for zero.

The job is to count the short "circuit breaks" while the first switch is on, and then emit that number. More info: Pulse dialing

Wiring

See the pin layout here.

  • Common wire (white) to VCC
  • Pulse wire (brown) to Pin 9
  • Op (green) wire to Pin 8
  • 10K ohm "pull down" resistor between GND and Pin 8
  • 10K ohm "pull down" resistor between GND and Pin 9

Launch

Open the code in the Arduino IDE, connect your Arduino board to a USB port and upload the code to the board.

Important note: Some boards do not support debugging. If you decide to debug with tactical outputs (Keyboard.print or .println), be very cautious. You may face a hard time updating the code again as it will output the debug messages into the active window - the Arduino IDE.

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Using an old rotary dial phone as your numeric keypad. Just numbers, no operators.

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