How would I create a 4Hz circuit from 9VDC?

Question

How would I create a 4Hz circuit from 9VDC?
What size capacitor would create 4Hz in a 9VDC circuit?

Answer 1

Making 4Hz from 9VDC requires an astable oscillator circuit. You can see many of these here:

http://www.uoguelph.ca/~antoon/gadgets/555/555.html

Halfway down the page it shows the schematic for the astable oscillator. If you make C1 = 4.7 microFarads, R2 = 22kOhms, and R1 = about 33kOhms, it will produce a frequency of about 4 Hz. Make R1 an adjustable resistor to get the timing exact.