Here’s a super handy/easy circuit for making LED eyes blink for your Halloween gadgets and projects, Paul writes – “The eye blink circuit consists of a timer and light emitting diodes, which function as the eyes. The timer circuit for the blinking eyes is based on the 555 timer. Figure 1 illustrates the standard timer circuit. The resistors and capacitor on the left control the charge and discharge of the circuit, which runs the pulse rate and duty cycle of the timer. The values in Figure 1 were chosen for a eye blink rate of approximately a second or two and a duty cycle of 85%. This simulates the blinking rate of eyes. The variable resistor allows the eye blink rate to be adjusted.” – Link.