I'm B. Tech Final year student of EE.Recently I'm working on "Speed Control of DC Motor using DAC".Please send me PDF file For this Project.So I can Work it out.
Using the DAC method, the output of the DAC varies according to the binary input variable varies: the transistor is polarized at the DAC output and, therefore, changes the motor speed connected through. While on the back, PWM instead of giving fixed voltage provides a mean change in voltage by changing the duty cycle - giving ones and zero instead of fixed analogue voltege. As the duty cycle varies the average voltage varies and hence the motor speed of DC.
The PWM method for controlling DC motor speed has certain advantages over the DAC method. Although DAC can provide a precise reading, but the disadvantage is that the biased transistor at the output of DAC operates in the linear region which is responsible for the continuous loss of power due to the drop of the emitter-collector (Vce). This could weaken the batteries in the long run. On the other hand, the transistor at the output of the PWM generator, eg the microcontroller, works only in the saturated or cut region, due to the fact that PWM generates alternates and zeros against the fixed analog voltage in the case of DAC.