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Electronics => Electronics => Topic started by: MaltiK on January 23, 2009, 02:57:18 PM

Title: Why need motor controller if an MCU has PWM output?
Post by: MaltiK on January 23, 2009, 02:57:18 PM

.?

Title: Re: Why need motor controller if an MCU has PWM output?
Post by: airman00 on January 23, 2009, 03:14:07 PM

because a MCU pin can only handle around 40mA of current and motors draw much more than 40mA

Title: Re: Why need motor controller if an MCU has PWM output?
Post by: MaltiK on January 23, 2009, 07:02:30 PM

Ahhh, ok and can any output pin on a MCU connect to an h-bridge to create a PWM cycle to be used by a motor, or does it have to be a PWM pin?

Title: Re: Why need motor controller if an MCU has PWM output?
Post by: izua on January 23, 2009, 07:28:14 PM

You can create the PWM signal in software, but that ties the MCU to that task.

Title: Re: Why need motor controller if an MCU has PWM output?
Post by: MaltiK on January 24, 2009, 08:32:37 AM

Ahh right so it doesnt have to be a PWM Output made by the manufactorer, I can check the C++ library on this site and dedicate a couple of outputs to PWM right?

Title: Re: Why need motor controller if an MCU has PWM output?
Post by: izua on January 24, 2009, 09:24:23 AM

Unless you do somthing like SSC-32, you'll be limited to a few. And by limited, I mean your MCU can't do anything else but software PWM.

Title: Re: Why need motor controller if an MCU has PWM output?
Post by: Admin on January 29, 2009, 08:26:21 PM

Open up the datasheet of your mcu and *read* it ;)

Probably on the first 2-3 pages you will see a pin out. Look for the pins that say PWM or OC01A or OC01B . . . stuff like that.

Title: Re: Why need motor controller if an MCU has PWM output?
Post by: Webbot on January 29, 2009, 10:28:56 PM

Quote from: MaltiK on January 24, 2009, 08:32:37 AM

Ahh right so it doesnt have to be a PWM Output made by the manufactorer, I can check the C++ library on this site and dedicate a couple of outputs to PWM right?

My C++ library in the member tutorials generates PWM in software, for DC motor controllers, so can actually use ANY output pin.

The library also includes hardware PWM for driving servos on the dedicated PWM output pins.