pwm numbers

[CharlieWilken]

Does anyone know the approximate numbers for pwm output on the victor 884s?
for example
127 = nuetral
when is full speed first reached
what would 1/2 speed be
what would 1/4 speed be
what would 3/4 speed be

Im not looking more for practical than theoretical considering a 130 pound robot? Did anyone test this?

thanks in advance

[10intheCrunch]

Ummmm...I believe if you calibrate your Victors, it will work linearly.

PWMs are pulsed voltages, so the farther from 127 you are, the more often the voltage is pulsed. At 254, the voltage is a solid 12V, and your motors will work as hard as they can.

If you are thinking in terms of when the *motors* reach full speed etc, no one can tell you. That all is going to depend on the load they are under, conditions around them etc. Your motors will work faster when the bot is on blocks than on the carpet...the only thing you really know is the voltage that is output to them (or average voltage, as its still pulsed at 12V).

Hope I didn't misunderstand your question...

[The Lucas]

From page 18 if the 2004 Programming Reference Guide :

PWM Speed Controller
Full Forward = 254-227
Neutral = 136-123
Full Reverse = 0 - 37

So there are your full speed and nuetral numbers. I don't know if calibrating the speed controller changes this (I hope not). I believe the Victor 884 speed contorller varies the duty cycle (percentage of time motors recieve 12V, the voltage "averages" out over time) linearly between these values. So 181-2 should be 50% duty cycle or half speed (averages to about 6 V, I really should scope this).

It ultimatly depends on the motors you use and thier partcular torque-speed curves. I have noticed that the CIM motors have low end torque issues. When given low pwm values they have a tendency to simply stall. For example: if you use CIM and Bosch for drive motors, you probably will notice the Boschs moving before the CIM motors. We used a program fix for this last year.

Well I guess I was a little too thoeretical I sorry about that. Hope it helps. Good Luck