I wanted to build something different and found this stop light kit online. Yeah I know I could have made the same thing easier with an Arduino. But I find it relaxing to just solder in parts without having to think about what your doing. This kit uses a HEF4017BP IC chip which is a PHILIPS - 5-stage Johnson counter. It also uses 3 transistors to drive the 4 sets of leds and has a crap load of zener diodes to make the counter work. The light change timing sequence is adjustable via a pot, and the whole board is powered by a regular 9v battery. The cost was $15 USD.