555 Timer Design Using MATLAB

Presented here is a Matlab program to design an astable multivibrator of desired frequency and duty cycle using a 555 timer. The aesthetic graphical user interface of the program helps you quickly calculate the values of timing components for your design requirements.

Fig. 1 shows the graphical interface where the desired frequency and duty cycle can be directly entered to calculate the value of timing components by the program.

Fig. 1: GUI 555 timer designer

Let us first discuss the basic functionality of a 555 timer to better understand how the Matlab program works.

Fig. 2: Internal diagram of a 555 timer

555 timer
The 8-pin 555 timer is one of the most popular ICs in the electronics world. With just a few external components it can be used to build amazing timer, pulse generator and oscillator applications. A popular version is NE555, which is suitable in most cases where a ‘555 timer’ is specified.

Fig. 2 shows the internal diagram of a 555 timer to help you understand its pins’ functionalities:

Fig. 3: 555 timer in monostable mode

Fig. 5: Astable mode of 555 timer

Pin 1: Ground terminal. All the voltages are measured with respect to this terminal.

Pin 2: Trigger terminal. This pin is an inverting input to comparator-2. It is responsible for transition of the output of flip-flop from set to reset. The output of the timer depends on the amplitude of the external trigger pulse applied to this pin.

Fig. 6: Flow-chart for the Matlab program