Building Propeller Clock from LED Display

This mechanically scanned propeller LED clock was made from 7 LEDs that gives the illusion of number in the air as it spins.

During operation, a PIC16F84 microcontroller keeps track of time and changes the pattern of 7 LEDs with exact timing to simulate a 7×30 array of LEDs while the propeller is spin by the motor. The illusion of a flat image is produced by the moving LED array. The power source comes from the spinning armature of a plain DC motor since the clock is on a spinning piece of perfboard. The bearing from one end of the motor was removed that leaves a big hole in order to run the wires out of the motor. In most small DC motors, the 3 terminal inside acts like a 3-phase alternating current. By taking one of the phases straight into the microprocessor, the motor position is detected.

For the 16C84, an 18-pin socket is used since it needs to be programmed before being placed in the circuit. A DIP resistor array was used for the 7 current-limit resistors. To keep the clock running after turning it OFF, a 47000uf super capacitor.

Rest of the project