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Unread 20-05-2011, 02:19
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Re: PWM speed controllers cheaper than Victors?

Quote:
Originally Posted by ProjectZero View Post
W... As long as I make certain the Arduino can output a PWM signal in the correct range to control it, we should be good.
Yes, the Arduino can do PWM. The thing to keep in mind is what exactly you mean when you say "PWM".

When we use the term "PWM" when we are referring to FIRST robotics, it is usually understood that we are talking about "hobby PWM" specifications. Hobby PWM usually runs at ~50Hz with a pulse width of 1ms to 2ms. This is usually the signal that feeds a speed controller, a servo or a "servo motor" like a Vex motor.

The speed controller, servo etc. contain electronics that interpret the "PWM" signal and then modify the output to the motor accordingly. For example, Victors and Jaguars both put PWM signals directly to motors. The Vic at 100 Hz and the Jag at 15Khz IIRC. The key is, the outputs to the motor go from 0% duty cycle to 100% duty. They also reverse the polarity of the output to control the direction of rotation of the motor.

The Arduino is capable of generating both hobby PWM and 0% to 100% duty cycle PWM. In fact, the later is done natively in the Arduino.
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