H bridge speed control

Prettybird

·I am working on my 3rd robot and just got a H bridge program running that I got here from a forum friend. The chip is very similar to the LM 298 and works fine. I am now planning to add speed control for feedback or closed loop applications. I am use to servo programs but don't know how to pulse the enable for speed control in the subroutine. I know I can do it with a relay and resistors or a 555 timer but would like to do this with as few external parts as possable. My programming sucks I admit but can modify if I have some good examples. I searched the forum archives some but found nothing. As usual thanks in advance for any help. Any pointers would be appreciatted. Here is a copy of the program I am starting with. Opps I think I should have put this post in robotics but don't know how to move.

Post Edited (Prettybird) : 10/23/2009 9:53:44 AM GMT

agfa

Sounds like your going to need to generate a·PWM signal which will require external components.· I've seen examples of circuits using 555s and others with gated oscillators.· Google PWM circuits and you should find lots of examples.


edit:· Heres one.

www.robotroom.com/PWM.html

Post Edited (agfa) : 10/24/2009 1:32:44 PM GMT

Prettybird

Thanks alot. I did some more research on H drives and the stamp in the forum archives and found out the stamp can't do it. They suggest using their PWM pal. I also found out that the Pololu 2 motor driver would work with less I/O space but more programming to learn. Mabe the prop could do more when I ever get motivatted to jump into it. I do have 555 timers and a Pololu driver laying around. This robot is completely made of leftovers. Anyone have a pololu 2 motor bot program laying around I can hack? As ususal thanks in advance for any helpfull pointers. ·Thanks again for the response. I hate running into walls. lol

Post Edited (Prettybird) : 10/24/2009 4:33:43 PM GMT

agfa

I've used the pololu micro dual serial motor controller, both as a controller and to generate pwm for larger motor drivers.· I thought it was easy to use and a good product for the price.· I'm playing around with·the prop now, I think its the only way to go.· I have some line following code I created for the bs2 with the pololu controller if your interested.·

agfa

Prettybird,

Here it is.