Society of Robots - Robot Forum

Electronics => Electronics => Topic started by: mattscott251 on October 06, 2009, 05:18:29 AM

Title: speed/direction controllers
Post by: mattscott251 on October 06, 2009, 05:18:29 AM

Hello, I am new to robot building and have been looking around for as much information as I can get online. When searching about speed controls, google gave me a book that under its dc motor section, mentioned direction control and then speed control. Is an h-bridge enough to do both? Or what exactly do I need here to be able to control the motors with an rc remote? heres the site of the book

http://books.google.com/books?id=2uIiY50yHQMC&pg=PA235&lpg=PA235&dq=how+to+attach+a+motor+to+the+wheels+on+a+robot&source=bl&ots=-XBX1KlZfj&sig=Wu1MR2lRbCkG3rjNpiRzdE-dv5k&hl=en&ei=69zFSpSKFtTO8QbnrPlG&sa=X&oi=book_result&ct=result&resnum=6#v=onepage&q=how%20to%20attach%20a%20motor%20to%20the%20wheels%20on%20a%20robot&f=false (http://books.google.com/books?id=2uIiY50yHQMC&pg=PA235&lpg=PA235&dq=how+to+attach+a+motor+to+the+wheels+on+a+robot&source=bl&ots=-XBX1KlZfj&sig=Wu1MR2lRbCkG3rjNpiRzdE-dv5k&hl=en&ei=69zFSpSKFtTO8QbnrPlG&sa=X&oi=book_result&ct=result&resnum=6#v=onepage&q=how%20to%20attach%20a%20motor%20to%20the%20wheels%20on%20a%20robot&f=false)

its at chapter 18, page 253.

Any help is appreciated.

Thank you!

Title: Re: speed/direction controllers
Post by: evilknight007 on October 06, 2009, 08:49:50 AM

Yes. a H-Bridge is enough to do both directional and speed control..
Speed control can be done by PWM.. its basically switching the motors on and off at a very high speed. the time interval between the on and off signal determines the speed of the motors.
A good tutorial on PWM can be found here .

http://www.societyofrobots.com/member_tutorials/node/229 (http://www.societyofrobots.com/member_tutorials/node/229)

Title: Re: speed/direction controllers
Post by: mattscott251 on October 06, 2009, 09:08:08 AM

So in order to do PWM, I need a microcontroller and I need to program it?

I want to be able to control my motors with a remote. Can I just have an h-bridge? The tutorial goes in depth and explains things well, but I just can't extract from it how to do what I want to do. I have a remote, the receiver, and a motor. I want to control that motor with the remote. I have read about h-bridges and pwm, but I just need some sort of dumbed down explanation of how to do this.

Title: Re: speed/direction controllers
Post by: waltr on October 06, 2009, 10:56:31 AM

What do you mean by "remote"? This it an RC (Radio Control) transmitter for models that have servos plug into the receiver?

If so then there are commercial motor speed controllers that plug into the receiver.
http://www.rc-truckncar-tuning.com/rcspeedcontroller.html (http://www.rc-truckncar-tuning.com/rcspeedcontroller.html)

Is this what you are looking for? They have circuits that interprets the 1-2ms servo pulse and the PWM switches the motor to control speed.

This can be done with purely analog circuits or with a mircocontroller. Since mircos are cheap and versatile (to change the function just load new code) they are the choice for experimenters.

Keep googling and you'll find lots of info on have to control an H-bridge for direction and speed.

Title: Re: speed/direction controllers
Post by: mattscott251 on October 07, 2009, 05:05:03 AM

"This it an RC (Radio Control) transmitter for models that have servos plug into the receiver?"

Yes that is correct. And the link you posted was very helpful. But what is the difference between ESC/MSC and H-bridges and why would I choose one over another. And if I were to opt for a microcontroller instead, what else do I need besides it and what would some recommendations be for what I get? I do have an Altera de1 board for school, if that can be used somehow. Otherwise are there any good step-by-step tutorials about them? Like an idiots guide or something?

Title: Re: speed/direction controllers
Post by: waltr on October 07, 2009, 02:28:17 PM

I'm not sure the the ESC verse the MSC controllers but the description implies that they are for different motor types.

The Altera board should be fine for read the width of the servo pulse out of the RC receiver then controlling the PWM duty cycle to an H-bridge.
By using a uC you can use one of the simple H-bridge boards that are available from a number of sources. Some are advertised to the right of this forum.

Here are some H-bridge links:
http://www.modularcircuits.com/h-bridge_secrets1.htm (http://www.modularcircuits.com/h-bridge_secrets1.htm)
And from our forum's sponsor:
http://www.societyofrobots.com/schematics_h-bridgedes.shtml (http://www.societyofrobots.com/schematics_h-bridgedes.shtml)

A little googling should find a few more.

Title: Re: speed/direction controllers
Post by: mattscott251 on October 07, 2009, 09:54:14 PM

ok. I think ill go to the library and try to find a few books. thanks for all your help!  :)