Fritzing

Generating pulses with the 555 Timer IC and change the frequence with a fariable resistor.

Experiment with IC Timer 555 shows a simple unsymmetrical pulse generator.

Schematic schows an asymmetrical pulse generator.

For R117=R116 you can use:

f = 1/( 2.1 * C212 * R217)

For detail signal pulse pause differentiation use:

f=1/(timpulse + tpause)= 1/( ti + tp )

ti= 0.7 * C212 * R217+R216

tp=0.7 * C212 * R216

Detailed calculation for schematic example:

f = 1/ (0.7 * C212(R217+2R216))= 1/ (0.7 10nF(33k+66k)= 1/0.462 sec =1443 Hz