Claw Motor Not Turning On Correctly

VEX V5 General Discussion Technical Discussion
#1

When I hit a button, I want my claw to open and stay open. Likewise, when I hit another button, I want it to close and stay closed, not release tension, dropping the cone. My students have written the code to do this but it eventually becomes unresponsive or only opens a little. The motor seems to lose power (or interest) in what we are trying to do. When we wait a few seconds, it starts back up. The students wrote code to turn off the motor. We thought it might reset the motor, but this didn’t make any difference. Currently I have an if statement followed by an else if statement to make the motors go in their respective directions. I don’t want to put in a blank else statement with 0 power because that’s what I’m trying to avoid. Is it overheating and this is causing it to stall? Your help is greatly appreciated.

#2

VEX EDR motors aren’t smart motors, meaning they don’t lock. So the claw motor might be at zero, but it can still go all over the place. If you stick a blank else statement that sets the claw motor to like 10, though, this will keep it closed but not give it enough power to move against the controller.

#3

Would there need to be two blank else statements with 10? One for the opening and one for the closing?

#4

I tried the 10 power with a blank else statement and it helps to hold it open really well. But to close it (which is more important) it of course slowly moves.

#5

It sounds like the motor is overheating. What power are you sending it?

#6

If the motor is trying to move at a high power level ( > 70) but not going anywhere, it will overheat and cut out pretty quickly. It should be able to stay at a low power level (~20) for a long time without cutting out. I recommend when you push the button, the claw initially moves at ~80, but after a short time (.5s) goes down to power ~20. This way, it will close quickly but won’t overheat

One simple way to do it is with a separate task.
Example:


task ClawControl()
{
  while ( true )
  {
    if ( vexRT Btn5U ] == 1 )
    {
      motor claw ] = 80;
      wait1msec( 500 );
      motor claw ] = 20;
    }
    else if ( vexRT Btn5D ] == 1 )
    {
      motor claw ] = -80;
      wait1msec( 500 );
      motor claw ] = -20;
    }
  }
}
#7

@Rod I wouldn’t use tasks just for braking power.
@Panther Tech Try this method:


int brakingPower = 0;
task usercontrol(){
	while(true){
		if(vexRT[Btn5U]){
			motor[claw] = 127;
			brakingPower = 10;
		}
		else if(vexRT[Btn5D]){
			motor[claw] = -127;
			brakingPower = -10;
		}
		else{
			motor[claw] = brakingPower;
		}
		//Other usercontrol stuff.
		delay(20);
	}
}
#8

@sazrocks So, that entire code is a separate task bracket than my primary?

#9

That’s the idea. It’s not the most efficient way to do it, but it will work.

#10

@Panther Tech @Rod No that code is not in a separate task. That was the point of my implementation, to remove the need for a separate task and allow this code to be run in the user control task. For this reason I named the task usercontrol and commented where to put the rest of your user control code.

#11