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benderman
Posts: 15
Joined: Wed Dec 17, 2014 8:19 am

New to robotics

Wed Jan 07, 2015 1:11 pm

Hi Guys,

I'm looking to build a basic robot powered by my B+ and I was wondering if someone could explain in simple terms the difference between motors and continuous rotation servos and the pros and cons of each please?

I've been looking on the web and I'm still not clear what would be the best to go for as a beginner.

I'm thinking a simple design of two driving wheels and a third for support, to be controlled by python and a wii remote.

Thanks,

Ben

Ravenous
Posts: 1956
Joined: Fri Feb 24, 2012 1:01 pm
Location: UK

Re: New to robotics

Wed Jan 07, 2015 1:23 pm

A continuous rotation servo is effectively a motor, a gearbox and a motor driver/controller built into one box.

A lot of people drive these (and regular, non-continuous servos) directly from the GPIO pins of the raspberry pi. You need pulses of the right frequency and width, but bits of software like pigpio or servoblaster can do these. (Power connections are needed too but that's another subject - might work directly off the raspi's 5V supply for a very small robot.)

I'd say the continuous servos look a good way to get a small robot working. Some places sell them cheaply in pairs with wheels.

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joan
Posts: 15051
Joined: Thu Jul 05, 2012 5:09 pm
Location: UK

Re: New to robotics

Wed Jan 07, 2015 1:28 pm

My simplistic summary.
  • Stepper motor: can rotate continuously, precise in-built position control, needs motor driver board, 2-4 gpios for control (usually 4).
  • DC motor: can rotate continuously, no in-built position control, needs motor driver board, 2-3 gpios for control.
  • Normal servo motor: can only rotate half a revolution, in-built reasonably precise position control, in-built motor driver board, 1 gpio for control.
  • Continuous servo motor: can rotate continuously, no in-built position control, in-built motor driver board, 1 gpio for control.

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