The ‘Arm Install’ example project in VEXcode V5 is used to display the potentiometer values on the V5 Brain, set the motors to ‘COAST,' 'HOLD,’ or 'TARGET' to move the motors so that their associated potentiometers are within the targeted value range. This project is used during the building of the Workcell in V5 Workcell STEM Lab 1.
This article will cover each of the options on the V5 Brain’s screen and why you would need to use that function of the project.
For details on how to open and use an example project in VEXcode V5, see this VEX Library article.
Joint Values
When you run the ‘Arm Install’ project, the V5 Brain displays the potentiometer values of the four joints on the Workcell.
Each joint has a predetermined range of potentiometer values. The V5 Brain will indicate if those values are within the predetermined range (PASS) or not within the acceptable range of values (FAIL).
Using potentiometers on the V5 Workcell ensures that it was built and assembled properly. The potentiometers are required to be installed at a certain position and at a certain rotation so the Workcell knows its 'home location' and functions as intended. For more information about potentiometers and how they function, see this VEX Library article.
‘TARGET’
The ‘TARGET’ option will move the motors connected to the potentiometers at each joint on the Workcell to their target location. The targeted location is the approximate center of the accepted potentiometer range.
Potentiometer ranges:
- Joint 1: 1600 - 2000
- Joint 2: 1900 - 2400
- Joint 3: 1700 - 2100
- Joint 4: 200 - 650
When the target option is first selected, the motors at each joint not within the target range will begin moving. While the motors are moving, a ‘Y’ or ‘N’ will appear next to each potentiometer value. This indicates if the target has been reached (‘Y’ for yes) or not (‘N’ for no).
Because the target is at the approximate center of the range, you may see the potentiometer value as passing (‘PASS’), but the target is not being reached (‘N’).
Once the potentiometer values are within range and within the target values for that joint, the line of text on the V5 Brain associated with the joint will show ‘PASS Y’ in green.
Note that this process may take up to two minutes to complete. The Workcell is moving in slow increments to ensure the potentiometer associated with that joint is within the targeted range.
‘HOLD’
The ‘HOLD’ option holds the four motors on the Workcell in place.
This can be useful while installing the arm onto the base of the Workcell. Movement of the gears and shafts connected to the motors could knock the potentiometers out of their accepted range. Holding the motors steady can help to keep those values in the passing range.
Note that the motors on the Workcell may still shift, even in the ‘HOLD’ position, if enough pressure is applied. This could damage the motor and move the potentiometer into the failing position. Ensure care when attaching the arm onto the base of the Workcell.
‘COAST’
The ‘COAST’ option allows the motors to freely move. This can be useful while adding the mastering jig into the build so the joints can easily move into position.