|Skema Rangkaian Variable frequency oscillator|
The principle component of this type of work does not change but each manufacturer makes the IC design and technology different. Almost all manufacturers make this type of component, although with a different. For example National Semiconductor LM555 call it, Philips and Texas Instruments SE/NE555 call. Motorola / ON-Semi designed with CMOS transistors that power consumption was small enough and called it MC1455. Philips and Maxim make his version of the CMOS ICM7555 name. Although different names, but the function of each diagram and pin compatible with each other. It's just that there are several different specific characteristics such as power consumption, maximum frequency and so on.
HereNE55 is wired as an astable multivibrator ,whose out put frequency can be varied by varying a potentiometer.This circuit is a must in the work bench of a electronic hobbyist.Frequencies ranging from several Hz to several KHz can be obtained using this circuit.For very low frequencies (few Hz) replace C with a higher value electrolytic capacitor.
The values of R and C can be obtained using the following equations.
1/f = 0.69 * C * ( R1 + 2*R2).
% duty cycle = 100*(R1+R2)/(R1+ 2*R2) .The good option is to select R1 in K Ohms and R2 in M Ohms.