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Unread 22-12-2004, 18:39
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Kevin Watson Kevin Watson is offline
La Caņada High School
FRC #2429
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Re: Victors Non-linear!!!

Quote:
Originally Posted by MikeDubreuil
Exactly,
It's general knowledge that the Victors pulse 12V to the motors to control their speed. Except at the extremes when the FET's give the full 12V. It would be very difficult to measure this on a general purpose multimeter.
You can with a true RMS meter.

Quote:
Originally Posted by MikeDubreuil
I am extremely skeptical of the voltages you are getting. A better test would be to see if the frequency is linear. I plan on checking that when I get back to the lab after the holidays.
Actually, the frequency is fixed. The duty cycle is what changes. This too can be measured directly with some higher-end meters, like the Fluke 189.

Edit: I wrote some code that shows how to generate the PWM signals using the PIC's CCP hardware. It's here: http://kevin.org/frc/edu_led_pwm.zip

-Kevin
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Kevin Watson
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Last edited by Kevin Watson : 22-12-2004 at 18:42.