June’s Component of the Month is the diode, and a 7-segment display actually consists of seven light-emitting diodes! So, why not matrix them up?
Skot Croshere built a matrix out of 512 7-segment displays: he calls it the DigitGrid:
The DigitGrid is an array of seven-segment displays. There are 4096 LEDs, forming 512 7-segment digits (they are actually 8 leds each if you count the decimal point). Every 16 digits is grouped together into a “module” with a Texas Instruments TLC5920 LED Driver/Controller. Each module has its own PCB with input and output headers. The modules connect together end-to-end to form rows of 32 x 2 digits. There are 8 of these rows. All of the rows are controlled by a Spartan 3E FPGA that also receives frames over serial. The various animations are written in Processing and then sent out frame by frame to the FPGA over 230kbps serial. The TLC5920 has a current limiting setting and as a result, the whole display draws less than 1 amp.
At some point while I was in school it became clear that the only way to satisfy my intrigue with 7-segment displays would be to build a massive grid of them. I had seen controller ICs such as the Maxim MAX6955, but the $10 ea. price tag (or $30 ea on Newark, WTF?) quickly made the project seem too expensive. Later during finals I found the TLC5920 at less than $3 ea! It was tough to resist the urge to start the project during finals.
(Originally posted by Matt Richardson.)
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