Bring 20th century telephones back with the rotary-dial cellphone
Many enthusiasts enjoying bringing older technology back to life, and one neat example is by Arduino forum member jeremie who shows us how to use an inexpensive cellphone as the transceiver for a rotary phone.
We find that this is a much cheaper and simpler method than using a 3G shield, as you can get such older-style cellphones for under $20 in pretty much any market.
The project is broken down into two main parts - an Arduino Nano-compatible board is used to read the pulses from the rotary phone dial; and the Arduino controls the cellphone via tapping into the phone buttons using digital outputs and optocouplers for isolation. For example:
It's a clever solution and saves you having to work with AT commands and more complex feedback from a GSM module. Once completed, the electronics can be re-fitted back into the rotary phone:
What a fun and interesting project, and would make a fun weekend project to share with children who haven't lived with the classic phones. To get started, check out the tutorial page.