Using a limit switch to limit motion

[charrisTTI]

Originally Posted by EricS-Team180

Four excellent posts there.

When using pots, consider using a delta when setting position limits. That is, pots can slip and the readings at your starting and limiting positions may not be what you originally set them to be. You can make pot calibration a pit maintainence item, but you can also make the starting and limit positions, variables, rather than hard-wired values. If you measure the change in pot reading from your initial position to your limit position....then:
1)At the start of a match, you can read the pot's start position.
2)Add the previously measured delta and set your limits to be used for the current match.
This helps prevent hardware damage, if you pot mounting has slipped.

Limit switches can be a blessing and a curse. In 2005, we had a lift on our 'bot that used shaft encoders and limits for positioning. We also included a manual override that ignored the encoders and simply depended on the limit switches. During the course of competition, our operator chose to ignore our lift position pre-sets - based on the encoders - and position the tetras manually. This put a real pounding on the limits that those of us in the pit did not realize was happening. In a quarter-final match at Nationals that year, the upper limit broke. Since our operator was running manual override, and we did not use the encoders as a back-up "limit switch" we actually pulled the entire lift out of it's base while on the field. (if you're goin' down, you might as well go down in flames - ha!) So, keep a bunch of spares and expect to replace them from time to time

The actual switch should not be the hard mechanical stop. Design the mounting of your switches so that something else takes the force of the overdrive.