I had an issue where I did not read the instructions properly for this excersise where you need to open the Serial monitor (Tools, Serial Monitor) Ctrl_Shift+ M and you need to enter the speed value for the motors.   That along with the switch on will move the motors.  Just double check that.  I wasted a couple of hours on that silly mistake and even bought new motor boards thinking it was faulty.  Hope that solves your issues.

It took me a while to figure out about this exercise too. Make sure your robot is connected to the system. You need to open serial port by clicking on tools from the top-bar. Then write the command like
f 50
then press Ctrl+Enter to execute. 

I hope this helps.

This is an old post, but if anyone else has problems with 5A and it doesn't have to do with the serial monitor, make sure your motor driver is placed fully into the breadboard. Usually other parts from the kit don't need to be pushed in all the way, but the motor driver needs to be firmly placed. That was my issue for the motor not moving. 

I am now in Unit 7 reading and one of the most important parts I have found of a robot is the actuator. This device not only converts energy into physical motion but also actuators produce rotary and linear motion, which I find very fascinating. In researching further about actuators, I found there are three major types of actuators; hydraulic, pneumatic, and electric, and depending on the kind of robot we are building one could be more suitable than others.

Hi Silas,

Hope you're enjoying the course so far. I felt the exact same way when I was opening the SparkFun Inventor's Kit. It felt rather familiar from previous experience playing with some of the LEGO Mindstorms kit (though I never had a whole set to really dive into) and from a course I took in college where I had to build a remote controlled "battle bot" type vehicle. Though, since it was all remote controlled, there was very limited programming involved.

It seems like we have similar backgrounds when it comes to this course.

So far, I've enjoyed the course quite a bit and I've learned a lot about the Arduino! Seems like you're a bit further in the course than I am, so I look forward to seeing what you do as your final project.