The ticker circuit composed of ne555 and cd40 17 is connected with a 5V power supply resistor. How to calculate the capacitance?

555 plus 40 17 is two yuan. You don't need to use a single chip microcomputer. You need a computer, a programmer or a download line to use a single chip microcomputer. The resistor and capacitor refer to RC with timing of 555. Changing RC can change the frequency, that is, the speed of the ticker. This circuit has no requirement for duty cycle, so it is convenient to choose RC. When the 555 timer constitutes a self-excited multivibrator, the period of the rectangular pulse output by the 555 timer is: t = 0.7 * (r1+R2) * C. When the integrating capacitor of the 555 timer is charged, the duration of its high-level transient is: t1= 0.7 * (r1. The duration of low-level transient is T2 = 0.7R2 * c, so according to the speed you need to estimate, it is best to adjust one of the resistors to make the speed change satisfactory.