Minibot switches...

[Retired Starman]

I was asked to be LRI for Peachtree this year since Ed Sparks couldn't take time off from his new employment. I instructed our minibot inspectors to allow all microswitches since the KOP microswitches were listed on the bag label as "limit switches."

Any switch that you would find behind the plastic plate on the wall of your house (the ones that turn your overhead lights on) is what I consider a common household light switch. Those were approved, and I feel, what the GDC had in mind for use on the robots.

For any other switch (all of which COULD turn some sort of light on), we asked for documentation stating that a function of this switch was to turn on lights, the idea being that such a general specification might suggest control of a light which might be found in, say, the range exhaust hood light in the home. While it didn't come up, I would have rejected a rocker switch specifically sold as an automotive switch because that's not a household application. I did reject a number of dubious switches, some of which had been severely modified, some of very questionable and foreign design.

I believe the GDC's intent was for teams to use the wall switch as described above. If teams want to play with me to see just how far they can push the envelope, then I will play with them, requiring the documentation for their specific switch, as asked for above.

It sometimes amazes me just how much work and grief people are willing tolerate just to do it some more difficult, less efficient way. It's so easy when you do it right!

[boomergeek]

Originally Posted by Mike Betts

By their nature, limit switches are usually momentary devices. A better choice would be a light switch...

JMHO,

Mike

After messing with heavy light switches, Team 241 decided on limit switches.

Creating a simple high friction hinge over the top of a KOP 3-way limit switch is a lightweight and effective way to short the motors when you reach the top- the friction in the hinge keeps the limit switch from turning back on.
A high friction hinge can be as simple as a small piece of angled aluminum with a machine screw that is double nutted to adjust compression/friction)
The KOP limit switch is very easy to mount to a vertical member of your minibot. Adding a travel stop on the hinge to protect the switch is also advisable.

If you have a super fast minibot, the hinge allows longer contact with the tower plate while in excess of 4N.

[Al Skierkiewicz]

Originally Posted by jvriezen

This might deserve clarification from GDC Q&A, but I don't see anywhere that its been said that you have to purchase a switch from the source that markets it as a limit switch.

From the Q&A for team 599 answered on January 24.

4) A limit switch is anything marketed as a "limit switch".

Ike, in all of the literature that I have checked this year for these types of switches (manufacturer sheets mostly) either the product family or the switch type has a listed use as "limit switch". Some of the pushbutton switches which I think you are referring to I have found are listed as limit switches by their manufacturer.

As to light switches, the wallbox was included in the original definition, changed later by the GDC in a team update. While certain regions allow some switches to be marketed as light switches, you may not find these in your area due to local electrical codes. If you can find a manufacturer's cut sheet for this product that lists it as intended for lighting control, print it out and bring it with you. The GDC has been firm that a switch that is not listed as a lighting control cannot be used even if the switch is used for lighting by other manufacturers in products they manufacture. (i.e. appliances, under counter lights, table lamps.)

[Tristan Lall]

Originally Posted by IKE

Yes, but 2 of the 3 are not marketed as such from their sources. I agree with you that almost everyone knows this.
There are some other switches that I really want to use that I have found at Lowes or Home depot in the home lighting section. The packaging says push button switch. It is a 125V switch that can clearly be used to turn a light on at home. It is readily available, but I don't know if every inspector will let me use this.

There is a switch at Radioshack that I would love to use. I found it in the limit switch drawer, but it is labeled "push button" on the packaging. I have found other "push button" style switches as limit switches on other websites. Much like the "limit" switch in the above example says "micro switch" not limit switch.

If possible, can you take a series of* pictures of the switches in their natural habitats? If from the context of the store display, it's apparent that these are being sold as a particular kind of switch, I'd say that counts as "marketed".

Whether it's a good idea to make teams systematically go to these lengths in order to use a simple part is a question the GDC needs to consider on their own.

*It's the 21^st century; photography is free. All teams and inspection stations have computers. No sense in reducing the discussion to the interpretation of a single photo; the more context in the form of close-ups and panoramas of the home lighting section, the merrier.

[DonRotolo]

Originally Posted by Al Skierkiewicz

Don,
I looked at Mouser and at Cherry Switch and could find no mention of "limit" in either location. If you have a page where this switch is listed as a limit switch, you merely have to bring a copy with you to show the inspection team.

Exactly what we did Al. See the attached image. That got it approved in NJ, but I have no confidence that it'll be approved in VA or CMP.

Now I am just as unhappy with the GDC on this issue as anyone, since all they did was make us scour the web looking for someone calling the device we wanted a "Limit Switch".

Certainly outside the intent of the rules (and not morally right, either), but anyone could set up a web page selling a "limit switch" and the poor inspector would have to accept a printout of that page.

Team 75 showed us a nifty trick for the top shut-off switch: Take a KoP microswitch limit switch (they ARE listed as "limit switches" on the manufacturer's data sheet - look for the words "end of limit"), bend the lever into a "C" shape, and it will latch under the body of the switch when pressed downwards. (Let me know if I have to post a photo).

[Al Skierkiewicz]

Tristan,
You may have missed the discussion with inspectors. The GDC has been very clear and the switch can be used if the card or packaging in which it is sold says "light switch" or "limit switch" or if the web catalog includes any of those words. Merely being a switch in the lightswitch area does not a lightswitch make. We do not have any room for interpretation nor regional acceptance of a switch that is used for one purpose but is not marketed by the manufacturer for that purpose.

[Tristan Lall]

Originally Posted by Al Skierkiewicz

Tristan,
You may have missed the discussion with inspectors. The GDC has been very clear and the switch can be used if the card or packaging in which it is sold says "light switch" or "limit switch" or if the web catalog includes any of those words. Merely being a switch in the lightswitch area does not a lightswitch make. We do not have any room for interpretation nor regional acceptance of a switch that is used for one purpose but is not marketed by the manufacturer for that purpose.

I agree with you that merely being a switch in the lighting section is not sufficient. There needs to be evidence that the switch is commonly available, and intended for use in a household lighting application. (The Q&A has referred teams to Team Update #12, which states "'light switches' permitted on the MINIBOT are not confined to those used in wall mounting boxes; anything sold as a 'light switch' for household use is allowed".)

The question of how something is marketed came up in the context of limit switches. (There, the GDC's standard said "marketed", not "marketed by the manufacturer". Indeed, that's why we accept vendors' websites as evidence.)

Applying the same "marketed" standard to light switches (which I agree is reasonable), I would have to say that if the store places it in a display that implies that this is the purpose of the device, then that satisfies the definition of marketing.

As a hypothetical example, Home Depot has a bin in their home lighting aisle that contains a number of unmarked switches, loose and unpackaged, and without an identifiable manufacturer's name. The shelf label below this and other bins is "Light Switches (120 V AC, 3 A)". Above the bins, there is another shelf displaying some household lamps, one of which uses the switch in question. I interpret that as evidence that the switch is marketed by its vendor as a household light switch—but we wouldn't have known that from examining the nonexistent packaging or cash register receipt. A full photographic record of the circumstances under which the switch is sold, though perhaps not contemplated by the GDC as a form of evidence, could be sufficient in my view to establish compliance with the rules. (And if the photos are not clear, or only show the switch in its bin without any of the other context, or don't show that the switch was used on a household lamp, then too bad; the team hasn't provided enough information. The team needs to meet a very high standard of proof.)

In other words, manufacturer's or vendor's documentation is a preferred method of demonstrating compliance—but the actual enforceable requirement is what's spelled out in the rules (as clarified by the update), and not merely the presence of that documentation.