My team has a crunch bot. There is a problem with the arm, whenever you raise it, it falls slowly if you let go of the up button on the controller. I know this isn’t a torque problem because the builders have installed a 84T instead of 60T gear for the arm, also, when you just select ‘run’ on the controller ( not selecting run under a program you have made, just the normal ‘run’ on a controller) it doesn’t have this problem, so it must have something to do with the programming. Any solutions?
Set the brake type to hold in your code. This will make the arm hold itself in the position it stops in, and raise it up if it falls down.
Brake types-
Coast: Motors stop, and can be moved around without resisting it
Brake: Motors stop and will stop you from moving it, but once it’s moved they will stop in the new position
Hold: Motors stop and stop you from moving it, and also move back to the position they started braking in if they are moved
19 Likes
Also - consider reducing this problem in hardware by adding some rubber bands to hold your arm up.
Setting brake type to hold will hold your arm up, but the more force the motors are resisting, the faster they will overheat and motor current will start to be limited for safety.
Ideally you would have rubber bands holding up most or all of the arm’s empty weight so that the motor is only doing the work of moving the arm around (plus holding up whatever cargo the arm might be carrying – in your case, a single ball, which is fairly light) rather than holding the whole assembly up against gravity.
18 Likes
I concur. Banding is amazing and the Kepler Electronics guide to DR4B’s shows some great examples of how to properly use elastics. Don’t get thrown off by the complexity of the build. The basic concept applies to anything that you want to repeatedly move along a pre-determined path.
5 Likes
I considered this but it would hinder our robot in several ways so I decided to just use the code option.
If your robot with a lift is hindered by rubber banding, you’re doing something wrong.