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-   -   How to power Mini-PC on robot? (http://www.chiefdelphi.com/forums/showthread.php?t=154152)

Jon Stratis 24-01-2017 11:20

Re: How to power Mini-PC on robot?
 
Marshall, I think you're reading too much into the Q&A ruling. It specifically says that "laptops are designed to have a battery" - even if the battery is swapable, that doesn't mean you're constrained to the one that originally shipped with the laptop, so long as you use a battery intended for use with that laptop by the manufacturer.

But I can't see a way to interpret that ruling to allowing batteries to be added to a computing device that is designed to be run off wall power. Before you try that route, ask a direct question on the Q&A, otherwise you're likely to be disappointed at competition.

marshall 24-01-2017 11:59

Re: How to power Mini-PC on robot?
 
Quote:

Originally Posted by Jon Stratis (Post 1635564)
Before you try that route, ask a direct question on the Q&A, otherwise you're likely to be disappointed at competition.

I did ask a direct question and got a "go read the dictionary" response. They were being cute with that response and they know it.

I'm already disappointed... nowhere to go but up from here.

Jon Stratis 24-01-2017 12:07

Re: How to power Mini-PC on robot?
 
Q138 was intentionally worded to be extremely broad, don't deny it. Any attempt to give a detailed response by the GDC would have likely opened up loopholes for teams to exploit. Instead, they gave a simple response that most people can conceptually understand.

Q284, on the other hand, was an extremely straightforward and narrow question, and as such got a straightforward and direct response. Be more like Q284.

marshall 24-01-2017 12:12

Re: How to power Mini-PC on robot?
 
Quote:

Originally Posted by Jon Stratis (Post 1635592)
Q138 was intentionally worded to be extremely broad, don't deny it. Any attempt to give a detailed response by the GDC would have likely opened up loopholes for teams to exploit. Instead, they gave a simple response that most people can conceptually understand.

Q284, on the other hand, was an extremely straightforward and narrow question, and as such got a straightforward and direct response. Be more like Q284.

Asking them to explain the meaning and intent of a rule is broad? I think not. I wasn't being cute. I was being sincere and trying to get a response.

I'd like to see one of two things:
A) Say that teams can use batteries for computing devices provided it is done safely and doesn't interface with the control or motors for the robot. This can be demonstrated by having the team turn off the robot and see what is still running.

or

B) Make the only legal source of power on the robot to be the ROBOT battery.

Bkeeneykid 24-01-2017 12:16

Re: How to power Mini-PC on robot?
 
Quote:

Originally Posted by marshall (Post 1635594)
Asking them to explain the meaning and intent of a rule is broad? I think not. I wasn't being cute. I was being sincere and trying to get a response.

I'd like to see one of two things:
A) Say that teams can use batteries for computing devices provided it is done safely and doesn't interface with the control or motors for the robot. This can be demonstrated by having the team turn off the robot and see what is still running.

or

B) Make the only legal source of power on the robot to be the ROBOT battery.

Both of those options bring up a lot of concerns that I don't think FIRST will agree with. With option A, you have the potential of teams connecting batteries to things that really shouldn't have batteries on them. You'd of course need much more changes in the rules to define what is "safely and doesn't interfere with control or motors for the robot". Option B means a lot of devices are now back out of the reach of teams, which kinda negates the original purpose of R37's lower info box. It's much too late in the season to implement that choice, as many teams are already designing in Phones ala 254 last year, GoPros and other small devices. I'd be ok with that first option, just as long as there's an explicit regulation on what it can and cannot power. Honestly, a single thread on CD and a few Q&A posts are unlikely to change these rules, so I'm not seeing that this could be implemented easily this year.

Jon Stratis 24-01-2017 12:22

Re: How to power Mini-PC on robot?
 
I understand what you want, but the rule is not written that way. That certainly could change in the future, but there's a whole world of safety related stuff that has to be taken into consideration.

If a team is improvising a battery and power system for a computer, do there need to be rules around wire gauge and breakers for that system? Do we need to check the system for grounding to the frame? Do wires have to be properly color coded? It's a whole can of worms you would be opening up here.

Allowing integral batteries solves that problem. GO PRO cameras can use their integral batteries without worry about burning up wiring or shorting out. Laptops can use their integral batteries while avoiding those worries as well.

So, FIRST really has a choice... have a rule written like it is in order to ensure batteries for COTS devices are implemented safely, or add another section to the rule book and another dozen rules to regulate what teams can and can't do. Personally, as an inspector, I prefer being able to rule on this simply without having to dig through a bunch of different rules for a situation that doesn't really come up all that often at events.

marshall 24-01-2017 12:25

Re: How to power Mini-PC on robot?
 
Quote:

Originally Posted by Jon Stratis (Post 1635603)
If a team is improvising a battery and power system for a computer, do there need to be rules around wire gauge and breakers for that system?

It's a custom circuit. There are already rules.

marshall 24-01-2017 12:28

Re: How to power Mini-PC on robot?
 
Quote:

Originally Posted by Bkeeneykid (Post 1635599)
Both of those options bring up a lot of concerns that I don't think FIRST will agree with. With option A, you have the potential of teams connecting batteries to things that really shouldn't have batteries on them.

You really don't. Limit it to cameras and COTS computing devices and you have what we have now.

Also, S03 already covers unsafe robots.

Jon Stratis 24-01-2017 12:38

Re: How to power Mini-PC on robot?
 
Quote:

Originally Posted by marshall (Post 1635606)
It's a custom circuit. There are already rules.

If we were to allow batteries like you want, please point out, in the current rules for custom circuits, what would stop me from putting a battery equivalent in capacity to the robot battery on board to power a custom circuit, and wire from that battery to the circuit with 28 gauge wire? Can you even pretend that situation should be allowed?

You would NEED rules just as complicated as our current power distribution rules for custom circuits if you allowed improvised powering of custom circuits from random batteries. For the sake of safety there just isn't any way around that.

Jon Stratis 24-01-2017 12:40

Re: How to power Mini-PC on robot?
 
Quote:

Originally Posted by marshall (Post 1635608)
Also, S03 already covers unsafe robots.

So you're OK with an LRI arbitrarily looking at a battery powered custom circuit and saying "I deem that to be unsafe"? You don't want rules in place to actually tell you what is considered a safe setup and what isn't?

marshall 24-01-2017 12:42

Re: How to power Mini-PC on robot?
 
Quote:

Originally Posted by Jon Stratis (Post 1635618)
So you're OK with an LRI arbitrarily looking at a battery powered custom circuit and saying "I deem that to be unsafe"?

It's already a rule and happens all the time to rookie teams.

Chris is me 24-01-2017 12:45

Re: How to power Mini-PC on robot?
 
I think it's vaguely clear that by "integral", they mean, like, the battery isn't an external device that plugs into the power supply port in lieu of a regular power supply. A laptop not only has a cutout for a battery, but a port purpose built for its use, and hardware integral to the laptop to regulate its charge. I think it's not THAT hard to understand the Q&A on this.

All of that being said, I think the rule is stupid and pointless and has no business making this distinction. USB batteries for custom circuits should be allowed. I know they aren't, so I won't use them, but they should be. It's silly that they aren't allowed, and it arbitrarily makes some solutions (more expensive ones!) better than others (more accessible ones!).

Rules for USB batteries don't have to be complicated. Allow a USB powered custom circuit to connect to it using standard ports and cables only. Make it like pneumatics where you can't modify the cables or the battery or use custom wiring or whatever. Maybe even regulate the size of the USB battery if you must. This is not prohibitively difficult.

marshall 24-01-2017 12:51

Re: How to power Mini-PC on robot?
 
Quote:

Originally Posted by Chris is me (Post 1635621)
I think it's vaguely clear that by "integral", they mean, like, the battery isn't an external device that plugs into the power supply port in lieu of a regular power supply. A laptop not only has a cutout for a battery, but a port purpose built for its use, and hardware integral to the laptop to regulate its charge. I think it's not THAT hard to understand the Q&A on this.

All of that being said, I think the rule is stupid and pointless and has no business making this distinction. USB batteries for custom circuits should be allowed. I know they aren't, so I won't use them, but they should be. It's silly that they aren't allowed, and it arbitrarily makes some solutions (more expensive ones!) better than others (more accessible ones!).

Rules for USB batteries don't have to be complicated. Allow a USB powered custom circuit to connect to it using standard ports and cables only. Make it like pneumatics where you can't modify the cables or the battery or use custom wiring or whatever. Maybe even regulate the size of the USB battery if you must. This is not prohibitively difficult.

No no, we can't have common sense here! We must all argue with Marshall about hypothetical rules he made up to help explain what kind of answer he was after from the Q&A people and their silly actual rules.

Andrew Schreiber 24-01-2017 12:51

Re: How to power Mini-PC on robot?
 
Quote:

Originally Posted by marshall (Post 1635619)
It's already a rule and happens all the time to rookie teams.

Or to any team that doesn't follow whatever inane whims some LRIs seem to have.



Pre-Edit: Don't read any subtext into this. If you think it's an attack on someone, it's not. Seriously, I'm not that subtle.

techhelpbb 24-01-2017 12:53

Re: How to power Mini-PC on robot?
 
Quote:

Originally Posted by marshall (Post 1635561)
So I truly do not understand what FIRST is after here. If they don't want external batteries then specify that.

If they are going to allow batteries for laptops then I truly do not understand why they think laptop batteries are integral. They are not required for a laptop to function. They are not essential to completeness yet that is how they defined it so I'm left to think that a battery must be required for a laptop because if it loses power then it will potentially corrupt the OS or files. Any 1st year EE undergrad can tell you that a power source is a power source yet FIRST doesn't seem to think that. Maybe a cell phone has a battery that is literally required for completeness but that's not strictly true either. All of these devices can be run from an alternative power source like the robot battery.

Now they've said that USB power packs shouldn't be considered integral. Well, ok... what about this: https://www.sparkfun.com/products/13896

IT USES A USB BATTERY PACK!!!

Not to mention the custom circuit rules which allows for other things like this:
Ebay link for a supercap based system that should be able to charge from the robot battery

USB batteries aren't legal but yet this thing seems perfectly legal provided it charges from the robot battery and doesn't power anything on the robot's control system or motors. IT MAKES NO SENSE! It's not a battery after all, it's just a bunch of capacitors in a custom circuit. Bonus, it has a built-in USB port.

I'm committed to kicking and screaming about this for as long as it is ambiguous and believe me, we'll push boundaries on trying stuff.

I really implore FIRST to stop and think about what this rule is trying to accomplish and then explain the intent. At this point they are just being silly.

I would like to third that an external battery properly engineered - should be just as safe as a in integral battery. Considering that certain products known to smoke have integral batteries that were not properly engineered either.

I believe I understand the spirit of the goal with this rule - but I disagree that integral batteries insure proper engineering and external batteries are more risky.

If it's down the bare legal issue of having someone to sue - consider that most companies DO NOT recommend mounting their systems on a mobile robot so in a Court of Law they'll pull that out as a defense.

Unrelated to the quote above:

I disagree that a small PC that is not a laptop will fair poorly on a robot. I know of several HP Pavilion models (550 for example) that are miniITX motherboards in unusually large cases and take 19VDC power in. With the addition of a cheap SSD these would be no more likely to fail than a laptop and that style board is often mounted in large full size motor vehicles. Granted a full size motor vehicle has a suspension. Years ago someone told me on Chief Delphi that a laptop on a robot would fail if it wasn't as robust as a Panasonic ToughBook so I put a Dell Mini 9 (SSD) and a Gateway netbook (with a HDD replaced with an SSD) on a robot in a box merely padded with foam and drove it over the 6" bumps in the field that year hundreds of times without a single failure of any sort. Could it fail - sure. Did it fail - no. I have watched people drop average HP and Dell laptops down stairs in a padded case in hibernation and they come out in one piece and still work.

As far as how to produce reliable power for such a setup - I strongly recommend that someone boost their input voltage from the battery as high as they are legally allowed then buck it down to whatever voltages they require (use switching power supplies). If 24VDC is the maximum (likely because of the history of the cRIO) then go as high as that. If you don't do this you'll always have risk that the battery will absorb a heavy load and drop output voltage just enough to force a reboot.

If would be better if your PC could run off 16V or less because at 19VDC you only have room for the input voltage to dive about 5-6VDC before the only safety you have to insure a correct output voltage will be the temporary charge of the internal switching power supply capacitors.

Finally I am still game to produce a 3D printed or laser cut case with a Raspberry Pi and battery in it but the requirements for this are more about FIRST rules than some huge business opportunity. If someone wants to put the work in I am will to provide assistance if asked. I figure the goal should be to provide such platforms for a bunch of common FIRST coprocessors because frankly - many times the coprocessors in FIRST are each powerful enough to run a mobile robot outside of FIRST and there could be some opportunity there if that business later provides expanded I/O solutions for those platforms as well. If someone designs the case I have access to many 3D printers and the large format laser cutters at NextFAB in Philadelphia. I can also provide free web services and domain registration to reduce the operation costs. I can finally provide testing and prototyping for the electonic elements. As I have effectively made this offer for this 5 times now on Chief Delphi alone - please be aware that you'd be working on something for next year because this year is cutting it very darn close and if FIRST (understandably) asks for something to examine themselves you are leaving them far too little time to complete that evaluation.


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