Circuits I’ve Recently Built

I helped a friend design a USB amplified audio dock for his Samsung Epic 4G:…p?t=980808&page=5

The other day I constructed a traffic light circuit. The way I did it was to set up an NE555 timer IC that fed into a 1 transistor NOT gate. This created a positive clock circuit. I fed that into a 4017 decade counter. The LEDs were then connected from 0-9 on the 4017. The yellow light only got 1 pin, and as a result only stays lit for a short time. The only drawback to this design is that I had to place a diode on each of the 10 outputs on the 4017 IC to stop current from flowing backwards when the output was inactive and low.

This is only one light. If I wanted to add a light for the other “street”, I could feed the 4017 output into some additional logic gates.