text: how can i achieve blinking of led without increasing cost when there are large no of leds???   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.