Victors Non-linear!!!

[Rickertsen2]

I have confirmed a suspicion i have had for a while. Apparently the victor 884's do not have a linear PWM input vs. voltage input.

A DVM was attached to a victor and the values recorded while incrementing the PWM input by a set number every 6 seconds. The reason for the initial values being a bit sketchy is that i was using a cheap digital meter that fluctuated a bit. As time went on, i got a little better at figuring what number it was hovering around.


Here i attached an unloaded motor to a victor and measured its speed vs. victor PWM input. The speeds were determined using a 1024 count optical encoder encoder. The motor was a fisher-price motor w/gearbox.
The test was automated and did the following:
1.set victor output
2.wait 2 secs for speed to stabilize
3.count encoder ticks for x secs. (I think the test was set to wait 3 seconds at the time this data was taken).
4.output data
5.increment pwm output and goto step 2 unless finished

Note that since the motor is unloaded, motor models dictate that speed should be directly porportional to the input voltage of the motor.


I should mention that these tests were done on a single victor 884 and i cannot guarentee that all victors behave similarly although i believe that they do. I also believe that this curve is a feature of their design.

There will be higher resolution data as well as code examples of how to compensate for this to come. It will probably be a while as i am busy with other things and will be out of town all this week.

I hope my imagehost holds up