can any one suggest me best method to control universal motor(hand tool) speed using microcontroller in minimum time ...

 

Is it DC or AC your talking about, what voltage?

 

Look up Fairchild app note AN-3006 for a start.
Max.

 

simple dc motor of about 24 V

 

simple dc motor of about 24 V

You state in your OP title Universal Motor.
A Universal hand tool motor usually just uses a simple Triac controller.
A portable hand tool runs off of DC it is not a Universal Type motor.
Max.

 

you can use a Tl494 pwm driver, remove vr1 and input your variable 5v dc voltage into pin 4, only one fet would be needed if its under 10amps.


http://electronica.mk/all_articles/Electric_Car_Projects/50A_PWM_DC_Motor_Speed_Controller/50A DC Motor Controller Schematic.png


OR you could use a ready made controller, using a 555 timer.

http://www.ebay.com/itm/12V-24V-36V...764?pt=LH_DefaultDomain_0&hash=item418d82efcc