Reverse Ramps???????

[cardinalman86]

Hey, we were just wondering if there was any way to slow a pwm down after a certain point. It would be almost like a reverse ramp we were thinking. I'm new at programming so I don't really know how i would do it. I also know that this is like a last minute thing so a quick reply would be great. Thanks in advance to anyone who helps.

Ps: this is so we don't bust our limit switch

[Tureyhall]

Originally Posted by cardinalman86

Hey, we were just wondering if there was any way to slow a pwm down after a certain point. It would be almost like a reverse ramp we were thinking. I'm new at programming so I don't really know how i would do it. I also know that this is like a last minute thing so a quick reply would be great. Thanks in advance to anyone who helps.

Ps: this is so we don't bust our limit switch

we use a pid (proportional input device?) for this. It speeds itself up the farther it is from its destination. However, you'll need an encoder or something for this.

If you can't find code for a pid loop on Kevin Watson's site, tell me and I'll see what I can do for you.

[DonRotolo]

Your LIMIT SWITCH should not also be serving as a HARD STOP. Overshooting the limit should not do anything to the switch. If your switch will be damaged by a movement, then your design is incorrect - move the switch out of harm's way.

Don

[EricH]

Originally Posted by Don Rotolo

Your LIMIT SWITCH should not also be serving as a HARD STOP. Overshooting the limit should not do anything to the switch. If your switch will be damaged by a movement, then your design is incorrect - move the switch out of harm's way.

And that's ANY movement. You'd think that mounting one to stop our arm would be fine. Nope. We mounted it too close to the backside's swing and then went to check the position of the one for the other side. Whirr (motors backdriving) tip (we tilted the bot forwards) click (throw arm hitting the floor). Followed by: "Uh...I think we need a new limit switch..." The switch still worked, but its arm was twisted and out.