Blog - Sketching with Hardware

Team 6 – A very early smartphone

Published on: | Author: Tatsiana Kocharava | Categories: 2017b, Best Projects, Projects

From the brainstorming to our great idea

For the implementation of the project, we decided to use a vintage telephone from the 1970s.



It should become the first minimalistic retro smartphone, which is to be extended by five features 😀. LED lamps are used to indicate the results of the pocket calculator and the mode you are currently using (for example, clock, radio, alarm or computer). They also illuminate together with the vibration alarm for the handset.

The concept

For the sake of time, we decided to create only three of five functions: time, alarm clock and pocket calculator.

  • An LED light should indicate the hour when the clock function is active
  • All the LEDs light up on the dial by a predetermined code when the alarm starts, when you are at the alarm clock mode.
  • The pocket calculator will first have only the  addition function. This is done by turning the dial to enter the numbers to be added, which then use a stepping motor to display the result.
  • The dial will then automatically return to the initial position.
  • A button next to the dial is used to switch from one function to the  next. On the display, and again with the help of the LED-lamps, we are shown in what function we are.


The development

We started disassembling the phone into its components, and removed the components we did not need.


We then cut two more holes into the turntable using a laser cutter. Then we proceeded with the composition in the form of a circle of the first 12 LED lamps. The challenge here was that they were not easily soldered together and had to be repaired and replaced by their instability.

Then came the LED lights for the display. So-called icons have been created for the display so that the functions can be betterrecognized when they are lit.


Then, the stepping motor was connected to the shaft clutch and the plastic gear. Subsequently, an insulation tape, which should prevent an unusual voltage drop in the motor house.



Other components that have been processed:

  • breadboard
  • microcontroller board (arduino)
  • stepper motor
  • stepper motor driver
  • power plug
  • piezo
  • 15 x LEDs
  • capacitor

These different pieces of the project are illustrated in the diagram




As software, we initially had a WLAN connection over x ESP8266 planned to synchronize the time over the Internet. Unfortunately, it turned out that ESP is unreliable. Therefore, we decided to use the millis method to calculate the current time. In this case, however, time deviations can occur. The code ist here


Last steps

At the end after assuring that everything was finally working properly we assembled all the phone together. To fit the stepper motor, we had to cut out a rectangular floor and four walls of Plexiglas. This served, among other things, to fit the stepping motor, as well as the stability of the housing. For the power supply another hole was milled.



In retrospect, the following problems arose:

  • The time was not exactly displayed, there were deviations
  • and the pocket calculator did not calculate the totals adequately
  • After copious checking of all connections between the components and the code, we came to the conclusion that it had to lie on the stepper motor, which apparently had not been sufficiently isolated.

The result




linked categories 2017b, Best Projects, Projects


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