This seven segment art display makes use of a 81 seven segment red common cathode LED displays. The LEDs are arranged onto 100x100mm boards that each contain an Arduino Nano and 9 seven segment displays, daisy chained through three-pin headers located on the sides of the boards. The pins (power, ground, and serial) provide the signals necessary for propagating a program across each of the connected boards.
The first board – with two Arduino Nanos – sends instructions for which digits to light and drives the display, sending the instructions over to the next board on the chain.
In a multiplexed arrangement, a single Arduino Nano is able to drive up to 12 seven segment displays, but only 9 needed to be driven for the program, keeping D13’s built in LED and the serial pins free. Since no resistors are featured on the boards, current limiting is done through software. This was inspired by the Bubble LED displays on the Sinclair Scientific Calculator, and was done in order to achieve a greater brightness by controlling the current through the duty cycle.
The time between digits lighting up is 2ms, giving them some time to cool down. The animations in the demos featured falling and incrementing digits, as well as a random number generator using a linear feedback shift register.
Source: DAISY CHAINED SEVEN SEGMENT ART DISPLAY
