== Circuit ==
* A discrete astable BJT multivibrator feeding into a johnson decade counter74HC595 shift register, which drives the LEDs directly.* The counter shift register can serve up to 10 8 segments.* The LED matrix can partitioned partitioned arbitrarily column-wise: multiple columns can be grouped onto a single counter output.* each counter shift register output has one series current limiting resistor* last multiple display modes:** blink (unusedCLK goes into enable) counter ** fill slowly, clear slowly (last output inverted feeds back )** fill slowly, clear at once (last output inverted goes to reset)** rotate (last output feeds back)
* multivibrator speed can be adjusted with a pot
* on/off switch?
* LED, $0.04650 @ 1000: http://search.digikey.com/us/en/products/WP710A10SRD%2FD/754-1593-ND/2769819
* CD74HC4017 decade counter74HC595N,112, $0.4776 378 @ 50100: http://search.digikey.com/us/en/products/CD74HC4017E74HC595N,112/296568-259891484-5-ND/480317763088
* CR2032 holder, $0.4968 @ 100: http://search.digikey.com/us/en/products/3003/3003K-ND/227448
* PCB 5cm x 10cm, $1.498 @ 50: http://www.seeedstudio.com/depot/fusion-pcb-service-p-835.html