Spinning LED Display – Schematics

To create our spinning LED display we needed to create a way for the board to communicate with each LED individually. It was important to use an odd number of LEDs so that we could create letters and numbers with a center arm, like E, H, and A. We decided to use 7 LEDs because this number creates a nice height for each letter, and makes the display readable at a distance. The LED display was constructed by creating a ground bus on one side of the breadboard and connecting the cathode of each LED to it. The anode of each LED was then connected to a 100Ω resistor, which in turn connected to a wire which led to the input pin that would control the LED. (refer to schematic below) In this way we were able to send information to each individual LED.

We also needed a simple way to turn the motor on and off, we decided on a slide switch to meet that need. This was created by connecting the positive wire from the motor to ground and the negative end to the center pin of the slide switch. The leftmost pin of this switch was connected to ground while the rightmost pin was connected to 5V. For a bit of fun we created an on/off LED, which was accomplished by running a resistor from the center pin of the switch to the anode of the LED and the cathode was connect to ground. We would advise caution not supply the ground and 5V required to run this circuit from your microcontroller as this practice permanently disabled one of our boards. Rather use some other source of power and ground, like the large breadboards supplied in the lab.