Re: Stopping motors
 

I have a shaky understanding of this myself, but I'll try to explain and hopefully an expert will come along and clear up any mistakes.

The Victors have a jumper on them, which you can use to select either "brake" or "coast" operation. When you put jumper in "brake", it will connect the output pins together whenever the input tells it that you want to stop the motor. What this does is "short out" the windings in the motor, and the way brush DC motors work, it makes the motor hard to turn fast. The motor can still be turned slowly, so this will not keep the arm from falling under all conditions.

When the jumper is in "coast", the Victor will leave the output terminals open circuit (disconnected), so the motor can be turned by the arm easily.

Team 1726 used a gas spring (like the black thingys that hold up hatchbacks on cars) to hold the arm up this year, the arm is very well balanced, and the motor does not have to work hard at all to move the arm, and the arm doesn't have enough weight to turn the motor when power to the robot is turned off. This might be the best way to solve your problem, IF your arm design has a place to put the spring.

If you could post some pictures of your robot, it would really help us figure out what you could or could not do to fix the problem. There are a lot of variables here...how heavy is the arm, what motor(s) does it use, what kind of gearing is on it, etc.