text: Even easier than using a 555 IC (my first inclination if you want an easily adjustable blink rate and duty cycle, at low component cost) is to just buy a blinking LED from Allied Electronics, part number 431-0096, at a cost of about 45 cents each (plus shipping). Digikey carries some with a blink rate of about 1.5 to 2.5 seconds in many colors, about 80-90 cents each.