PWM with LM555 vs Microncontroller ?

[asking]

Dear all,

Although i know..about PWM generation...with LM555 configured as Astable Vibrator... i need to how its different other than as Compared to PWM Generated by Microcontroller... i know Microcontroller can generate the Programmed PWM as required...can we get different duty cycle in LM555 ? or just like 10-20-30 % duty cycle ? i need to know the Cons & Pros of LM555 as PWM Generator..

I hope for some of you guyz, plz throw some light on this topic....

 

[BradtheRad]

I am looking for a similar thread listed at the bottom of this page, because someone asked about this recently...

Not finding it, so I'll post this schematic showing a simple method to vary the duty cycle coming from a 555, by applying different volt levels at the CTL pin:

 

[betwixt]

The biggest difference is in how you set the duty cycle. In an NE555 circuit you have to do it by component value change or by injecting a voltage in to the control pin as shown by BradtheRad. If you use a microcontroller it can be done numerically by passing different values in to the PWM (or software equivalent) registers. A micro will normally be more stable as the PWM rate will be decided by the system clock frequency and is relatively imune to temperature and small voltage changes.

The disadvantage of a micro is most derive the PWM speed by dividing the system clock and so cannot produce an infinately adjustable rate.

Brian.