"Black Box" Electrical Board

[FireAmpersand]

So with the school year starting up as well as pre-season, I've started to think of new ways my teams electrical board could be improved from the year before. And I've thought about an idea that is like a "Black Box" for the whole electrical board. The Box would contain most of the standard electrical system: Rio, VCM, PCM, PDP, Motors controllers and so on. There would be output cables plugs (Like a 15 Pin) on the out side of the box to output to things like motors or external sensors. So my question is would this be legal to use within a FRC Match? The Box would be Inspector Friendly, durable, and very easy to manage. Tell me your thoughts.

[EricH]

I think that WAY too much is going to have to depend on the implementation to make the call either way unless I had said box right in front of me. Can it work? Sure. It's been done before.

#1, you're going to need to make sure that all the appropriate lights can be seen by an inspector. Fail this, and you automatically lose "Inspector Friendly" (as well as having to rebuild the board to see the lights). That being said, there aren't too many lights on the boards that actually need to be seen.

#2, you're going to need to make the access easy (you want to be able to work on the stuff when you're not on the field, right?).

#3, make sure all your plugin points--motors, sensors, main breaker/battery, and anything else--is secure, well labeled, and ideally very difficult to plug in the wrong way. (Varying sizes of Anderson custom blocks for motors work; a 15-pin or maybe a 37-pin for sensors; also make sure you've got an appropriate pigtail for your programming cable.) This isn't inspection stuff, this is so that you don't get the wrong cable into the wrong spot.

#4: FAN. You'll need to cool the box somehow, what with all the electronics there generating heat.

[FireAmpersand]

1. Thanks for the quick and detailed reply.

2. The idea is like the picture but on a bigger scale, I plan to make it so we build the box once that way for every season we just do minor upgrades or replacements and don't do much to it.

3. Do the lights need to be seen just at inspection or all the time? If its all the time we can make the top out of some see through material.

4. We do have a Electrical Tech as a mentor, he can makes sure everything is snug and safe for the box. The best part with 15 pin plugs is most of them can only go a certain way so anyone can plug them in.

If all goes well i can also post a picture for people to comment on so that we can make sure this is legal for comp.

Once again thanks for the reply.

[FireAmpersand]

Also if done right it makes teaching first years electrical just by looking at the box and its wiring diagram

[EricH]

Originally Posted by FireAmpersand

2. The idea is like the picture but on a bigger scale, I plan to make it so we build the box once that way for every season we just do minor upgrades or replacements and don't do much to it.

There are some rules that would require building a new one every year. Not the least of which happens to be the fact that the robot design changes every year! That being said, building a new box on the same design would appear to be legal. At least under the 2015 rules.

3. Do the lights need to be seen just at inspection or all the time? If its all the time we can make the top out of some see through material.

I'd just make it out of see-through material. And here's why: It can make troubleshooting a LOT easier if you see all the lights! Inspection only needs to see a few, at inspection--but we'll generally expect to see them as the robot would be on the field. If that means opening the top of the box, you'll probably get a comment, but you'll probably also pass.

4. We do have a Electrical Tech as a mentor, he can makes sure everything is snug and safe for the box. The best part with 15 pin plugs is most of them can only go a certain way so anyone can plug them in.

As long as you aren't using 15-pin plugs for the power to the motors (or they happen to be for the appropriate wire gauge, which would be one NASTY 15-pin)! This is where Anderson connectors come in handy: you can build them into bricks of varying sizes, and match them exactly--say, 40A wires in one, 30A in another, 20A in a third... or should that be drive motors in one, manipulator motors in another? Pick something that makes sense. Makes life really nice, or so I hear. (I haven't had occasion to do that and pull the plug, at this time.)

If all goes well i can also post a picture for people to comment on so that we can make sure this is legal for comp.

Just for some clarification: You won't be sure until you get to your first official event of the season. Anything said on CD needs to be taken with a grain of salt. (Even if Al says it--though if Al says it, it's almost certain to be accurate.)

[Michael Hill]

I wouldn't want to be the electrical guy to tell the mechanical guys that they need to find room for my giant box o' electrons. To be honest, I like how modular the current system is because it lets your electronics fit in a confined space.

[Al Skierkiewicz]

My advice to teams always starts with a discussion of wire losses for high current loads. If you want high performance from your robot, my suggestion is to place the PDP near the center of all of your electrical loads. This make the wire runs short and reduces wire loss to a minimum. Add you motor controllers in a like fashion centered around the PDP. Follow that with my advice that adding connectors also raises the chance of a failure and loss. Keep connectors at a minimum and you will be much happier with the robot. Please keep in mind that the #6 wiring from battery to PDP carries all of your robot current. Keep this run short, direct and neat. Even #6 carries loss. If you are running 4-6 drive motors, you are passing 500 amps through this circuit. At typical lengths, 500 amps will drop at least 1/2 volt before the PDP.

[jojoguy10]

I saw team 4118's electrical box in person. It was a pretty good design. We're planning to do something similar.
https://www.youtube.com/watch?v=klMEioarUds

[MrForbes]

We've been able to make a box for the electronics only two of the past ten years. Something about the function of the robot driving the shape of the robot, driving the available location for electronics.

It's a neat idea, but may not be very practical.

[scca229]

Originally Posted by FireAmpersand

3. Do the lights need to be seen just at inspection or all the time? If its all the time we can make the top out of some see through material.

The FTA/FTAA would really like to be able to see the lights in the event of a problem on the field. The lights help with troubleshooting such things as:

• Did the Rio reboot?
• Did the Radio Reboot?
• Are the Rio/Radio receiving power?
• Is there network activity? (ethernet cable unplugged?)
• Many more I'm forgetting early this morning

It helps to be able to tell the team/inspector what we saw so that there is a starting point on getting it fixed and not missing a match. If you can help us with being able to see, we can help narrow down what the cause may be.

[evanperryg]

Originally Posted by EricH

I think that WAY too much is going to have to depend on the implementation to make the call either way unless I had said box right in front of me. Can it work? Sure. It's been done before.

#1, you're going to need to make sure that all the appropriate lights can be seen by an inspector. Fail this, and you automatically lose "Inspector Friendly" (as well as having to rebuild the board to see the lights). That being said, there aren't too many lights on the boards that actually need to be seen.

#2, you're going to need to make the access easy (you want to be able to work on the stuff when you're not on the field, right?).

#3, make sure all your plugin points--motors, sensors, main breaker/battery, and anything else--is secure, well labeled, and ideally very difficult to plug in the wrong way. (Varying sizes of Anderson custom blocks for motors work; a 15-pin or maybe a 37-pin for sensors; also make sure you've got an appropriate pigtail for your programming cable.) This isn't inspection stuff, this is so that you don't get the wrong cable into the wrong spot.

#4: FAN. You'll need to cool the box somehow, what with all the electronics there generating heat.

All of these, but especially #2 and 4. Trying to fix that thing inside of your robot between matches is going to be a nightmare if it isn't implemented right. Think about it- odds are, your electrical is already difficult to repair at events, and now it's inside a little box, and really close together. As a result of that closeness, #4 is a serious issue, too- I remember seeing a thread where someone talked about how they tried something like this, and their electrical system overheated on a regular basis. You'll definitely need some strong ventilation if you plan on making something like this.

[nuclearnerd]

I think it's a useful idea for sure - we might even try it ourselves this year, so thanks for the thread and responses.

I've attached up a potential layout using this enclosure from McMaster Carr, which has a clear lid so judges can see the lights. At 22" x 15" x 4", it should fit in a belly pan (depending on gearbox location), or elsewhere on the superstructure. Everything fits well inside, although you would need a separate enclosure / area for the pneumatic system. Fans, as suggested, should be added, as well as panel mount connectors for all the motors, etc.

(Open question: are we allowed to use a second Anderson SB-50 connector in the line between the battery and the PDB?)

[EricH]

Originally Posted by nuclearnerd

(Open question: are we allowed to use a second Anderson SB-50 connector in the line between the battery and the PDB?)

I believe the answer was "no" last year.* That being said, by being "creative" about the location of your main breaker, I think you can get away with using only one. Hint: Think (on the) outside (of) the box.



*Last year's rules do not apply to this year. OK, I said it, now the fine print: But I rather suspect that this rule/ruling will make an appearance in the rulebook/Q&A again.

[GeeTwo]

We always wait until we have at least a rough robot design before we start on the control board. The past two years, having a relatively large, flat control board worked well (belly pan, under the ball in 2014 Aerial Assist, and on the rear and low, but easily accessible for 2015 Recycle Rush). For AA, we arranged so the taller cRIO was to one side and the large parts of the pneumatics system were in the corners where they would not interfere with the ball. For RR, the roboRIO was low-profile, and we did not use any pneumatics.
In 2013 Ultimate Ascent, with the suddenly reduced frame perimeter and height (if you wanted to fit under the lowest bar on the pyramid, as we did) and complexity (throwing frisbees and climbing the pyramid were completely different!), the control board wasn't a board at all, but was (as described at the time by Allister, who was in charge of the control board) like playing 4-D tetris. Not only did he have to work in a cramped space, but it changed regularly as "team foundation" (drive and shooter) moved something, which displaced the climber, which in turn moved the controls around. If we'd had a preconceived control board, it would have been guaranteed not to fit.
In 2012 we DID lay out and install the control board after the drive was done but before the manipulators. We wound up cutting it in half to make room for the pneumatic cylinder that lifted each ball into the turret. Not pretty.
Besides, you never really know what needs to go onto the board - what if the controller you're planning to use is outlawed, or not needed? Do you really KNOW a priori whether you'll need pneumatics at all?
In short, design your control board like you design your robot -- for example, if you make advance plans for three or four basic drive systems, make advance plans for three or four basic control layouts. Then, wait until you've done your game analysis, strategy selection, and at least high-level robot design before you do your control system physical design.

[OccamzRazor]

This idea is relevant to a robotics team I was on at the university level. We used talons on this lunar rover for the NASA Lunabotics Lunar Mining Competition and they along with the rest of the sensitive electronics had to be fully enclosed because real lunar regolith (real regolith simulant used by NASA) will absolutely destroy motors, actuators, circuits, and clog any possible crevice because it also has an electrostatic charge.
https://www.youtube.com/watch?v=DaodHQC_MIo

We used these "black boxes" you see on either side to house our electrical systems and we plugged in with military grade dust proof connectors. They do work for FRC as well, but you may want to check for heat generation inside of the box and really see if simple fans will work. There are free heat conduction simulators online. It is really easy to make these boxes a nest of wires so use caution.