Newbie need help to make a motor run for a laser scanner and some questions I am trying to make a laser scanner consisting of a webcam and a line laser scanner. I have tried to use a manual scanning (by hand) and has worked, but would now like to consider automating the laser rotation (upwards and downwards) as a higher accuracy entails a slow and smooth rotation.

I came across arduino a few weeks back and realised it could possibly help to make this a reality. From my limited readings so far, I have obtained an Arduino Uno and a motor shield that seems to be the essentials for my purpose.

I have a few queries that hopefully someone can help:


Do I need a stepper motor for slow rotations, instead of a normal brushed motor?
Do I need to connect the Arduino to computer to make it run? Can I run it off battery, if so, does it have an 'ON' button?
How long will a standard 9V battery last?
For the code, I thought of using the simple one here: Arduino Motor Shield Tutorial.
Would it be able to allow me to control the amount of rotation, speed and the ability to reverse its rotation?
A servo motor would have a lot more control than a normal motor. You usually command them to go to one of the predefined steps (stops) by using a function call in the servo motor library.
You can run independently of the computer. Many people do this. Certainly you can run off a battery. It doesn't have an ON button, you normally would have this between your battery and the Uno (eg. built into the battery pack). Like this:





A 9 V battery? I wouldn't use one, especially to drive a motor. It won't last long. Get something like 3 x AA batteries in a battery holder.




To show you the idea, I have this servo motor (SG-5010) I got from Adafruit. 

I measured it using about 200 mA of power when operating. Now, I looked up a typical Alkaline 9 V battery, and found that, consuming 200 mA, it lasts for around 400 mAh. Thus, you could say it would be good for two hours at that rate. Plus, the Arduino will take around 50 mA, so maybe less than two hours.


A smallish servo motor won't need a motor shield. The pictures on the linked page show ordinary brushed motors. A servo motor has 3 leads:


Power (eg. 5 V)
Gnd
Data



Make sure you connect the grounds together, but the power could go to a separate power pack. A bit depends on how much power your motor will use. The data goes to the Arduino for the information about which rotation point to step to.

You should be able, in code, to change the rotation position, forwards and backwards.