Minibot switches and soft landings

[Andrew Bates]

Originally Posted by cgmv123

<G22> HOSTBOTS may not contact their ALLIANCE‟S MINIBOT while any part of it is above the DEPLOYMENT LINE.

At least in our setup, when the minibot can touch the deployment, the minibot is not above the deployment line.

[cgmv123]

That should be legal.

[Vermeulen]

@Brando

Hm, I guess I was misreading rule G22 as not being able to contact the hostbot after any part crosses the deployment line, and not as long as any part is over the deployment line. In that case, I don't know what our partner's red card was given for during that match, we just assumed it was a G22 violation.

[boomergeek]

Originally Posted by Vermeulen

@Brando

Hm, I guess I was misreading rule G22 as not being able to contact the hostbot after any part crosses the deployment line, and not as long as any part is over the deployment line. In that case, I don't know what our partner's red card was given for during that match, we just assumed it was a G22 violation.

If a deployer swings the minibot down, like a drawbridge, and as it comes down if any portion of the minibot is above the deployment line and simultaneously within the vertical cylinder of the tower and in contact with the deployer- independent of whether it is in contact with the pole, I think the referees will rule it in violation.

Here's a whole thread on it...

http://www.chiefdelphi.com/forums/sh...ent+cylind er

[waitwhat?]

Originally Posted by WarehouseCrew

I have two questions that I would appreciate help with. What specific electrical switch is working to turn the minibot off after the top pole sensor is successfully tripped (but not turning off without triggering sensor)? We have one push button switch from Home Depot that takes about 7 pounds of pressure to turn it off. The fuse may trip before this works.

Secondly, how do you make the minibot come down the pole to a "soft landing"? I've read that some teams are using reduced power on the motors to provide a braking action after the top sensors is reached. How is that done (eg. my switches are only on and off, no 1/2 power option) and is there a risk of burning up the motors?

Thanks.

Here is a little tip. McMaster Carr sells "Manual Reset limit switch" Part # 7336K51. Works like a charm. This will also allow you to create this circuit with EASE.

This is exactly how our minibot is wired....

[Ed Law]

Originally Posted by waitwhat?

Here is a little tip. McMaster Carr sells "Manual Reset limit switch" Part # 7336K51. Works like a charm. This will also allow you to create this circuit with EASE.

This is exactly how our minibot is wired....

Is that considered a legal switch according to the rules and all the Q&A?

[Vikesrock]

Originally Posted by Ed Law

Is that considered a legal switch according to the rules and all the Q&A?

Yep, it is marketed as a "limit switch" so it is allowed.

[Al Skierkiewicz]

Originally Posted by Ed Law

Is that considered a legal switch according to the rules and all the Q&A?

Yes it is. The McMaster catalog lists it as a "limit switch" and it is the application for which it is most used.

[TheCommander]

We did something a little different.

I took the Tetrix switch that is legal, took out the dremel, put on a cutting wheel and removed the on half of the toggle so that it is flush when the switch is in the off position. Now it only toggles to the off side, but can be reset to the on position.

We mounted the switch at the top of the mini-bot and when it hits the trigger it toggles and turns off the mini-bot. It can be mounted by cutting out a rectangle that is 1 inch by 1/2 inch and pressing the switch in. We designed the mini-bot a little more on the rugged side, so when gravity pulls it back down the pole it can withstand the impact.

The added bonus is that it mounts easily, is sturdy, looks nice, and the red on the switch lets you know the mini-bot is armed.

This just seemed like the simplest solution for our design and application.

[krudeboy51]

wouldn't the highlighted area on this pic cause the fuse to blow?

[11douglash]

What we did is find a 4 way light switch (i believe). Basically, it was a switch that flipped polarities. Then there was another switch that triggered when the robot hit the pole.

Our minibot went up, flipped the polarity switching switch, powered down, hit the bottom, and then, due to the mechanical way the wheels were rotating, fell off, and thus broke the switch that kept it powered, and turned off.

[penguinfrk]

This was the circuit diagram for our minibot.



When we short the motors, the current generated when backdriving will go through the circuit again the opposite direction. The result is a fairly slow terminal velocity when it falls.

Hope that helped.

[sumginazu]

Originally Posted by DonRotolo

I saw team 75's minobot with a KoP microswitch limit switch, where they bent the lever into a "C" or 'hook' shape so when it is pressed down, it 'latches' under the body of the switch and keeps the switch "off". Since it's a SPDT switch, they use the NO contact to short out the motors as described above.

I did the same thing with a simple momentary switch when designing the minibot my team used. The latch worked perfectly, but we had to be careful in ensuring that the switch consistently contacted the top plate - it didn't during one practice run, which ended with a burnt out motor.
Our minibot usually stayed at the top after it had finished its run because it did not weigh enough to backdrive the motors, which ended up being okay. Unfortunately, the minibot's momentum occasionally caused it to fall off the pole once it hit the top plate, and twice it hit the ground hard at the end of a match. We needed to repair it both times. As long as your minibot has a reliable method of attaching to the pole and it does not "free fall" after it hits the top, it should survive a trip back down. You should certainly test it to make sure, though.