Discussion
 

The 555 timer IC is a TTL compatible device that can operate in several different modes.
FIGURE 1 shows how external components can be connected to a 555 timer to produce a square wave clock signals or a free running oscillator.
The frequency of oscillations and its duty cycle are determined by the value of the external resistors, RA and RB and the external capacitor, C.
The formulas to obtain the values of the frequency and its duty cycle are given in the DIAGRAM.
You could see that it is impossible to produce a perfect 50% duty cycle square wave output.
However, it is possible to get very close to a 50 percent duty cycle by making RB >> RA while keeping RA greater than 1kohm so that t1 is approximately equal to t2.
 
 

OBJECTIVE | DISCUSSION | DIAGRAM | PRE LAB | PROCEDURE | RESULTS