Society of Robots - Robot Forum

General Misc => Misc => Topic started by: gshoger on May 28, 2007, 03:51:38 PM

Title: speed controllers
Post by: gshoger on May 28, 2007, 03:51:38 PM

where can i get some speed controllers?
if i use a speed controller and a motor, can that basically take the place of a servo?

Title: Re: speed controllers
Post by: Ro-Bot-X on May 29, 2007, 02:38:10 AM

Quote from: gshoger on May 28, 2007, 03:51:38 PM

if i use a speed controller and a motor, can that basically take the place of a servo?

Well, it can take the place of a modified servo for continuous rotation. But the DC motor has to be driven by a H bridge driver, and the use of PWM can controll speed.

With a servo you can calculate the traveled distance. The servo works in pulses that you need to generate every 15 to 20 milliseconds so the servo will rotate continuously. Depending on the wheel diameter, the robot will travel a certain distance for one pulse. If you measure that, you will be able to calculate how many pulses will be necessary for the robot to travel a certain distance.

You can do the same thing with stepper motors.

To do the same thing with a DC motor you need wheel encoders.

Title: Re: speed controllers
Post by: ed1380 on May 29, 2007, 05:09:13 AM

IIRC the speed controler splugs into a servo port and has battery imputs and motor outputs. it is used mainly by the RC world.

Title: Re: speed controllers
Post by: dunk on May 29, 2007, 05:52:56 AM

it depends on the type of speed controller.

you can get motor speed controllers that plug into radio controll equipment and take the same input as a servo.
you could use one of these and a motor in place of a modified servo.
try searching on radio controll sites for this option.

you can also get motor controllers that take a simple PWM signal from a microcontroller.
this kind will not work as a plug in replacement for a servo.

there are other more complex motor controllers out there that take rs232 and i2c inputs but these are less common.

dunk.

Title: Re: speed controllers
Post by: Steve Joblin on May 29, 2007, 07:02:11 AM

Try google...

There are lots of motor controllers available on the market... one one my favorites (for small DC motors used in "table top" sized robots is made by Pololu.  The Dual Serial Motor Controller is very easy to use and very inexpensive.... check it out at http://www.pololu.com/products/pololu/0101/ (http://www.pololu.com/products/pololu/0101/)

Title: Re: speed controllers
Post by: Admin on May 29, 2007, 06:30:40 PM

I list a bunch of places that sell 'em here:
http://www.societyofrobots.com/robot_parts_list_electronics.shtml

(they are often called motor drivers, ESC, motor controllers, etc.)