user15759: I have searched google and I now know that if we change the resistance, we can change the brightness of an LED, but I was wondering how to change resistance by using a micro controller.

user13432: Did you do a web search? "arduino pwm high power led driver" gives all the info you may need to answer this. 
Here is a nice youtube clip, by Julian Ilett that explains how to do this: 60W High Power LED Driver with PWM #2 - Brightness Control.

15759: <p>I have searched google and I now know that if we change the resistance, we can change the brightness of an LED, but I was wondering how to change resistance by using a micro controller.</p>
 13432: <p>Did you do a web search? "<a href="https://www.google.co.th/search?q=arduino%20pwm%20high%20power%20led%20driver" rel="nofollow">arduino pwm high power led driver</a>" gives all the info you may need to answer this. </p>

<p>Here is a nice youtube clip, by <a href="https://www.youtube.com/channel/UCmHvGf00GDuPYG9DZqQKd9A" rel="nofollow">Julian Ilett</a> that explains how to do this: <a href="https://www.youtube.com/watch?v=V7CA1brVXDA" rel="nofollow">60W High Power LED Driver with PWM #2 - Brightness Control</a>.</p>
