Servos and DC Motors

[NoThatsGay]

Hello, roboters

My high school's science club working on the $50 robot. It's the first time working with robotics for everyone involved. We're not sure exactly what the difference between a servo and a DC motor is, whether we need both, and exactly what kind(s) we need. We also aren't sure if we need a motor driver because of the lines:"Servos are DC motors with built in gearing and feedback control loop circuitry. And no motor drivers required!"

If you could clear this up for us, we'd appreciate it. Thanks in advance.

[knossos]

You can use servos or DC motors.  They are interchangeable, but they need to be controlled differently.  Also servos are typically restricted to 180 degrees of rotation.  They need simple modifications to make them rotate 360 degrees.  A servo, at heart, IS a DC motor with gears and extra circuitry.  Information on servos and how to modify them can be found in the tutorials section.  

[knossos]

You don't need motor drivers to control servos.  Instead you just send a PWM (pulse width modulated) signal to the servo to control it.  The length of the PWM servo will tell the servo what position to go to.  Typically a 1500 microsecond PWM signal will send the servo to its middle position.  Increase or decrease the timing to go one direction or another.  This diagram from ServoCity's website might make this a little clearer.

[NoThatsGay]

Which one would be more cost effective?

[NoThatsGay]

http://store.alshobbyshop.com/hs-322hdsixkarbongearservo.aspx

Would this be a viable option for our robot?

[Razor Concepts]

Yes