Minibot switches...
 

What kind of switch are y'all's teams using to cut the minibot off at the top of the pole?

Re: Minibot switches...
 

i would suggest using a limit switch that would kill the motor once it hit against the top of the pole.

Re: Minibot switches...
 

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

JMHO,

Mike

Re: Minibot switches...
 

good point. placed correctly, a light switch would probably work better

Re: Minibot switches...
 

I would use a DPDT home light switch or a DPDT Mechanical switch. That way you can make the Mini-bot come back dow after it hits the top.

Re: Minibot switches...
 

So is something sold as a "safety limit switch" still a limit switch?

http://www.automationdirect.com/adc/...Limit_Switches

These advertise pull-reset instead of momentary functionality.

Way out of my area of expertise here, but I wanted to make sure that "momentary" was not part of the definition of limit switch.

I also think teams could design their own latching mechanism for a momentary limit switch with a little aluminum and surgical tubing.

Re: Minibot switches...
 

Any chance for a picture? I just can't see how to mount that...

Re: Minibot switches...
 

a combitnation of a house hold switch on the top to turn it off worked. and once the bot hit the pole the minibot helped sending it up.

Re: Minibot switches...
 

Aaron,

Perhaps we can persuade Al to comment on this. Although I am sure that a "pull to reset" type of switch was not what they had in mind at game design time, it is marketed as a limit switch and, IMHO, legal.

Regards,

Mike

Re: Minibot switches...
 

As best I can tell what does and does not qualify as a limit switch is up to the marketing department of the electronic supply companies and the inspectors at each tournament.

Those who has been to multiple tournaments know that what passes inspection at one tournament may not pass at the next, or at the FIRST Championship Event. I could see a very engineering oriented inspector use a functional definition of a limit switch.

Globalspec.com has the following definition.
An inspector with this working definition wouldn't need to ask for documentation if a Cherry E79-20A showed up on a mini-bot as long as it was being used as a limit switch. Both Mouser and Digi-Key lump their switches into catagories. Snap-Action, Lever and Limit switches are lumped into the same family of switches in their marketing. On the Cherry E79-20A Digi-key lists it in the CATEGORY of switches and the FAMILY of Snap Action, Limit, Lever. The actual DESCRIPTION says SWITCH SNAP DPDT 10A QC TERM. The word LIMIT is not used. So, is it a limit switch? Is it being marketed under the Family of limit switches? Would every inspector come to the same conclusion on this? The GDC appears to place this decision squarly on the shoulders of the inspector to judge the quality of documentation.

Mouser has a similar switch from Omron Electronics. Their DESCRIPTION reiterates the general catagory "Basic / Snap Action / Limit Switches DOOR INTERLOCK SWITCH" However, the DATA SHEET doesn't use the word limit at all. It is a door interlock switch. Would all inspectors agree that this is marketed as a limit switch?

Lastly, the limit switches that have come in the kit of parts are huge and heavy compared to some of the other switches which are used as limit switches. A couple of smaller momentary switches that everybody can agree are marketed as limit switches include a small lever switch from E-stop and one from VEX.

I'd love to hear comments from inspectors on this issue. Thanks.

EDIT: I imagine that e-STOP only used the word LIMIT SWITCH in their online listing because they are aware of FIRST, and the restrictions we are under for this years game. Plenty of other vendors sell this switch without specifically calling it a limit switch. So, is it a limit switch because their marketing department called it one, or is it a limit switch because it meets the functional definition?

Re: Minibot switches...
 

Aaron - well said! I have been very frustrated trying to work this out with the GDC.

Just a clarification on the switches you mentioned. There is a similar part to the E79-20A. It's the Honeywell 2DM301.

The Omron part you mentioned is usually referred to as a "cheat" switch - on with door closed, off with door open, with optional override by pulling out the plunger during maintenance. Which could be still used for a steady ON or steady OFF, but one needs to be more careful about not reaching the momentary "plunger fully in" state.

--Karlis

Re: Minibot switches...
 

We are using both a limit switch and a light switch on our bot. The light switch is for the kill switch as it hits the top.

Re: Minibot switches...
 

Guys,
The Gdc answered this question a week or so ago. Their response is
"Only items sold as "limit switches" are allowed on the MINIBOT. Documentation and/or packaging material should be used to document items that may not be clearly identified as such. "
It seems that is pretty clear that any switch labeled as a limit switch meets the criteria.
As to the automationdirect link, those switches meet the criteria but the fact that they mount and wire using 1/2" conduit fittings likely make them too heavy for minibot use.
As to the other links that show "limit switch" in the title, likewise those fit the GDC description above. Inspectors are guided first by written rules (including all Team Updates) and second by GDC Q&A response. If the rules do not cover a situation and their is no response from the GDC on the issue, an inspector then turns to his LRI for the answer. If the LRI is not able to come to a conclusion, they will turn to the FTA, Head Ref, and other key volunteers for advice. If the issue still is undecided, LRIs will have my phone number and I will be able to get to someone at First or Bill Miller if needed.

Re: Minibot switches...
 

Thank you Al for the response. The word "Title" is a bit difficult to interpret. I have part numbers, descriptions, and family/catagories to look at in the Digi-Key and Mouser online catalogs.

Below is a breadcrumb trail for getting to a particular switch on Mouser:
Even though the final identifier is D2D-1001, I wouldn't consider that a title. The description is
So the level of identification immediately before part number contains the word limit switch. I guess that would have to be legal then? :ahh:

Somebody stop me if I'm going down the wrong path. ::rtm::

Re: Minibot switches...
 

That D2D-1001 looks like a winner to me. Just print the catalog page and bring it to inspection. :) What a hefty current rating too!

Re: Minibot switches...
 

So, just wondering if any teams have gone out on a limb and used a "switch" made from the allowed minibot materials with the purpose of mimicking a two-way switch but saving weight over a purchased item? If you've done this and been inspected at a competition were you allowed to compete in this manner? Feedback either way would be appreciated.

Re: Minibot switches...
 

tuy,
You can only use limit switches, a max of two lighting switches, and Tetrix switches on the minibot.

Re: Minibot switches...
 

That doesn't sound right to me, Al. What's the problem with fabricating your own switch using the allowable MINIBOT materials such as aluminum and rubber bands? Can you cite a rule or Q&A ?

John Vriezen
FIRST FRC team 2530 "Inconceivable"
Mentor, Drive Coach, Inspector

Re: Minibot switches...
 

John,
<R92> The following items are the only permitted materials for use on the MINIBOTS:
M. limit switches,
N. no more than two common household light switches,

The Q&A answered that only the Tetrix Rocker Power switch could also be used as it is a Tetrix part.

I am not aware that any other parts were approved as electrical and would expect that the Q&A would agree. In the case of the minibot, electrical using the list above, is the simplest problem to overcome. As always, the Q&A is the only definitive answer.

Re: Minibot switches...
 

If you can afford it, you can go the route my team went and replace the fuse on the battery lines with a lower-rated one (we use 7.5A) and blow it once you get to the top and briefly stall the motors. We replace that fuse every match.

It may not be the most cost-effective solution, but it's extremely simple.

-Nick

Re: Minibot switches...
 

we're using the tetrix power switch (and a custom aluminum lever) as well as the 7.5A breaker

Re: Minibot switches...
 

A breaker would not be permitted.

John V
FRC Team 2530
Mentor, Drive Coach and inspector.

Re: Minibot switches...
 

Agreed, breakers aren't allowed, but if you replaced the fuse on the tetrix battery with a 7.5 A fuse, that would be legal.

Re: Minibot switches...
 

Fuse, breaker - same thing (just as long as what's used is a fuse):rolleyes:

Our minibot inspector at NJ agreed that the Cherry E79 listing off Mouser said "Limit switch" somewhere and so he accepted it.

I just wish I could be confident it will be accepted in Virginia and/or CMP

Re: Minibot switches...
 

yeah, fuse, fuse... not breaker. sorry.

Re: Minibot switches...
 

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. The Q&A responded to a question from Team 599 "4) A limit switch is anything marketed as a "limit switch"."

Re: Minibot switches...
 

I really dislike the "marketed as" wording.

For instance, is this switch illegal (not marketed as a limit switch)

http://www.radioshack.com/product/in...er Value=SPDT

Are these too illegal (sorry, those are micro-switches, not limit switches)
http://www.mcmaster.com/#micro-switches/=bhhquw

Yet this one would be perfectly legal (It does have the term "limit" in its description):
http://www.amazon.com/Copper-Termina.../dp/B002P4XQY6


When the original Q&A called for a "light switch" as the kind mounted in a wall box, we made up some SPST, SPDT, and DPDT switches with blades and rubber bands, and mounting brackets and used a scale to make sure they applied 6N of force. When parents came in to look at the mini-bot, they laughed at me and explained there were way better switches at Radio-shack or online. This is funny the first time you defend the rule. The 20th time though, is pretty annoying.
Then update 12 came out to which I believed was a coming around to something more reasonable.
Now I am a bit concerned. I can find the same switch on 3 websites. 2 being frequent parts suppliers, but are those technically illegal? The other source I would rarely/never go to to buy an electrical component, but because it has the proper descriptor, should I? If I purchased switch XYZ from A (illegal description), and then show up with paperwork from C (legal description for the exact same switch), do I have to lie and say I bought it at C, or can I say i bought it at A, after finding it through C...

I will try to get our Q&A guy to post this question.

Re: Minibot switches...
 

Ike,
The three switches you link to are commonly shown and marketed as limit switches. Everyone knows them as limit switches, they come in the KOP as limit switches albeit with different actuators. Limit switches are legal on the minibot and have been from the first day.

Re: Minibot switches...
 

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.

When update 12 came out, I thought we were beyond the bring your packaging, bring the website, bring the marketing brochure from the manufacturer... but I have heard from other teams that their switches weren't allowed during week 2 events.

I am not trying to lawyer the rule, I am just trying to figure out how we will be held accountable for choosing the switch we choose to use.

Re: Minibot switches...
 

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.

If Mfgr X sells a limit switch with part # N through multiple marketing channels, and at least one of those channels 'markets' it as a limit switch (or household light switch) and you buy it through another marketing channel, that should be ok.

As a practical matter, anything that it is quite clearly something that 'ought' to be marketed as a limit switch or household light switch will not invite added scrutiny from an inspector. They don't have the time to be asking for documentation on every switch, only questionable ones.

In my point of view, the 'marketed as' requirement allows the issue resolution to go to a neutral third party and tries to avoid long drawn out arguments between an LRI and a team member. It provides a mostly cut and dried resolution path.

John Vriezen
FIRST Team 2530 "Inconceivable"
Mentor, Drive Coach, Inspector

Re: Minibot switches...
 

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!

Re: Minibot switches...
 

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.

Re: Minibot switches...
 

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.)

Re: Minibot switches...
 

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.

Re: Minibot switches...
 

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).

Re: Minibot switches...
 

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.

Re: Minibot switches...
 

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.