This simple counter can be used to count pulses, as the basis for a customer counter (like you see at the doors of some stores), or for anything else that may be counted. The circuit accepts any TTL compatible logic signal, and can be expanded easily.
http://www.aaroncake.net/circuits/counter.asp
This circuit uses a set of 13 differently colored LEDs to generate a full color spectrum. The spectrum could be extended on both the IR and UV sides. The circuit board can be mounted on a piece of white hardboard, the white paint reflects the colors nicely.
http://www.solorb.com/elect/misc/ledrbow1/
flashes the LED for a full year on a single 1.5 volt AA alkaline battery.
http://www.imagineeringezine.com/PDF-FILES/ac14fls.pdf
flashes the LED for more than a year on a single 1.5 volt AA alkaline battery
http://www.imagineeringezine.com/PDF-FILES/1vled3.pdf
The circuit below uses a hex Schmitt Trigger inverter (74HC14) and two 8 bit Serial-In/Parallel-Out shift registers (74HCT164 or 74HC164) to sequence 16 LEDs.
http://ourworld.compuserve.com/homepages/Bill_Bowden/page5.htm#4017-2.gif
The LED flasher circuits below operate on a single 1.5 volt battery. The circuit on the upper right uses the popular LM3909 LED flasher IC and requires only a timing capacitor and LED.
http://ourworld.compuserve.com/homepages/Bill_Bowden/page10.htm#15flash.gif
Canbe operated for approximate 12 months from a single cell.
http://www.discovercircuits.com/PDF-FILES/1vled3.pdf
This circuit makes a nice lamp that consumes little power, runs cool, and has an incredibly long lifetime. The lamp puts out a warm yellow shade of light, the color may be adjusted by changing the number of red or green LED strings.
http://www.solorb.com/elect/solarcirc/ledlamp/index.html
Putting a small light switch on the LEDs lets me turn the lights off so I can sleep and keep the fans running for my hard drives.
http://www.elephantstaircase.com/wiki/index.php?title=LEDFanSwitch
This code is for a simple RGB LED controller for 8 LEDs using a PIC16F628. The pattern is determined by the data in the EEPROM. Upon startup, the controller loads the data into RAM and starts up the sequence.
http://www.semifluid.com/PIC16F628_8RGBLED.html