Lesson-3.markdown

@@ -41,7 +41,7 @@ TBD: Code snippet? Limits: 80 and 200ms?
 
 ### Exercise 6
 TBD: Code snippet, video, calibration:-30, raw values are inverted compared to percent readings, PID control and gain choice.
-
+http://youtu.be/RL0ZnIF1B_o
 
 ## Conclusion