i have a project to handle with servo and im beginner with Arduino Uno. the problem is, i need to create a code that can servo rotates step by step. can continuous servo do that? should i use a potentiometer to control the speed?
can i control the step by use time (miliseconds) or set up the degrees? because i need around 1-3degree per step.
Your task is extremly difficult.
The servo takes positive pulses, 1ms to 2ms in in lenght (new pulse 20 times .. 50 times a second)
sending 1ms pulses, the servo spins at full speed one direction, at 2ms pulses: full speed oposite direction.
at approx 1.5 ms its stops.
It wll be very difficult to control how far the servo moves as u change pulswidth a litte away from 1.5 ms
You can tell the servo to move for a specified time and hope that it ends up moving the right distance, but without additional feedback there's no way to know how far it's actually moved. You could use a rotary encoder to inform you how far it has moved. Ideally the encoder tooth spacing would be chosen to match the size of the steps you want to take.
yup. definitely.. 
because i've control the speed by used potentiometer. i imagined the steps just like a clock rotation but i think it will never work. damn blurred rite now
can someone help me in coding. im bad with it.. sorry
ask for a stepper motor (and a motor driver)
If it would be sufficient for the servo to rotate a max of about 3 revolutions you could use a sail winch servo which can be rotated to a specific position.
If that isn't an option you will need some external position reference or a stepper motor.
...R
There are some servos that can do a little bit of both. You might be able to modify a less expensive sail winch servo to do the same.
http://www.robotshop.com/ca/en/hitec-hs785hb-servo-motor.html
one way is a rotary encoder. that is what is used on DC motors for CNC. and they have extremely precise control of 'steps' per rotation.
Thanks for suggestion.. I'll try to make it coz I don't want to ruin our budget. May be I need to control a very low speed to rotates the machine. Now was extremely difficult time for me.. wish me luck!
..find a outdated printer.. be a surgeon and get a stepper motor.