PDA

View Full Version : Question about using the "brake" on the 884


Caleb Fulton
03-12-2003, 08:24 AM
Have any of you noticed any real evidence of damage or extra wear-and-tear on the Victor 884's when the "brake" feature is used? Also...Would using the brake make a dead reckoning robot behave more like it is supposed to (the robot would stop when you tell it to)?

Josh Hambright
03-12-2003, 08:29 AM
Our team has not noticed any extra wear and tear.

Caleb Fulton
03-12-2003, 08:33 AM
Okay...here's another question: If the brake is on, will changes in the PWM input from 254 to...say...160 actually make the robot's speed reflect the change in speed? In other words: Will the brake help force the motors to go to the correct speed when they are slowing down?

Josh Hambright
03-12-2003, 08:38 AM
Ummm
Its to early in the morning for me to think...

I'll post a response during 5th hour...

Maybe Al or one of the more knowlegable people on here can post a response before me. They probably know more then me anyways.

Joe Ross
03-12-2003, 08:39 AM
Brake will not change the behavior of the robot when going from 254 to 160. It only takes affect when the output is 127. It shorts the motor leads, and the motor stops much much more quickly. You may see a slight difference when switching from foward to reverse (becasue it crosses 127), but you should only see it when stopping.

Using brake does put more wear and tear on the victor, because it has to deal with the back emf from the motor. However, the victor was designed to deal with it, and so it shouldn't be a problem. If it does cause a problem, then it is a design or manufacturing flaw, and you should get it replaced from innovation first.

Jeff Waegelin
03-12-2003, 09:08 AM
I know it made our autonomous program work better. Without it, we rolled about 4 or 5 feet extra, but with brakes, we stopped in less than a foot. There are a few problems, though. We've experienced some backflow of current when the motors stop, and it throws our program off a bit. We've since solved that problem, but it was very annoying during testing.

Al Skierkiewicz
03-12-2003, 01:51 PM
The 884's are not damaged and do not wear from the use of the braking function. As stated above, in "brake", the Victor produces a low resistance connection across the motor (which is now acting like a generator) and all of the robot motion is turned into electrical current which is shunted by the 884. If the brake mode is affecting anything on the robot, it is possible you have a high resistance somewhere in the wiring. Check for loose connections/crimps particularly in the negative side wiring for battery and power distribution.