Wire color...

[Al Skierkiewicz]

Jeff,
I would have made that same assessment. Green or green with yellow is a universal color for safety ground that implies a low impedance connection to a ground rod or water pipe. It is also the wire to which you should attach a ground fault interupter. Although there is no robot rule that covers this color, we do want to keep students using standard color codes so they don't get in trouble elsewhere.

[Joe Johnson]

Originally Posted by Al Skierkiewicz

...Green or green with yellow is a universal color for safety ground...

I think this is too strong of a statement. Automotive wiring uses green in many places for wires other than ground. Automatic equipment mfg do not limit themselves to non-green colors within their PLCs. There is a lot of green wire out there being used in non-safety ground applications.

If there is no rule against it, I think it should be allowed.

Joe J.

[texarkana]

Originally Posted by Al Skierkiewicz

Jeff,
I would have made that same assessment. Green or green with yellow is a universal color for safety ground that implies a low impedance connection to a ground rod or water pipe. It is also the wire to which you should attach a ground fault interupter. Although there is no robot rule that covers this color, we do want to keep students using standard color codes so they don't get in trouble elsewhere.

This is dead wrong. It is not the inspector's place to make up rules on the spot based on his own personal opinion just to teach a lesson. There are very few water pipes and GFI's in an FRC robot. If he wants to teach a lesson about house wiring and encourage students to not use green wire then he is free to offer that advice, but you do not make up rules and force teams to rebuild their robot at a tournament because you feel they used poor practice. There are 1000 rules of thumb about good mechanical and electrical practice that are not in the rules and you cannot ask teams to accommodate the pet peaves of every inspector. As a mechanical inspector I would not force a team to put lock washers under their nuts even if I felt strongly that they should, because it is not in the rules and it is not my place to add it. If the GDC intended for a wire color to not be used they would put it in the rules. The inspectors have a checklist for a reason.

[Al Skierkiewicz]

Whoa Tex,
I didn't say I would make the team remove it. I said I agreed with the assessment that green is a color used for safety ground. As such I would inform the team of my assessment and let them decide. Inspectors do have a responsibility to try and help teams. We are on the front line to help you be competitive because it is best for all involved. As green is often thought of as being a common/earth/ground/safety, an electrical person would walk up to help you troubleshoot and naturally think that the green is tied to battery common. If used in the output of a speed controller, that could allow a person to tie a meter or other electrical device to it thinking it was common and find a pulsed 12 volt signal there. Smoke may follow. In auto electrical, as Joe has pointed out, there are other color codes.
As always, teams have the right to question the inspector and ask the LRI for a ruling. An LRI will usually include the head ref and FTA in discussions that transcend the rules. As much as we try to help, teams often disregard our advice. A testament to this is teams who mount the breaker panel upside down and have breakers fall out or teams that attach chain sprockets directly to the shafts of CIM motors without the use of additional bearing surfaces and have the motors fail during a finals match. The list is long, these are just a few.

[texarkana]

Originally Posted by Al Skierkiewicz

Whoa Tex,
I didn't say I would make the team remove it. I said I agreed with the assessment that green is a color used for safety ground.

Ok. He said the inspector made them rewire it, and you said you agreed with that assessment.

[Danny Diaz]

Originally Posted by Al Skierkiewicz

As much as we try to help, teams often disregard our advice. A testament to this is teams who mount the breaker panel upside down and have breakers fall out...

Ouch. I happen to fall into this boat; we considered everything that could fall/hang/dangle off/down/from the robot's electrical system (which was mounted upside down as a safety measure against balls and to save space on the robot) - however, I guess we never considered the breakers falling out since we have a hard time pulling them out by hand as it is. But, I guess I can see how this is just another thing we need to consider. Any suggestions on how to guarantee the breakers don't fall out, other than mounting the board right-side up? Has that been a problem with the new Power Distribution Boards?

-Danny

[Al Skierkiewicz]

Danny,
I was speaking to the old fuse blocks. The new PD holds pretty tight until it has been used repeatedly. However, if your robot comes off the bump hard, it might pay to think of a way to put a piece of lexan over the breakers that will not obstruct their view for inspection.

[joeweber]

Originally Posted by Danny Diaz

Ouch. I happen to fall into this boat; we considered everything that could fall/hang/dangle off/down/from the robot's electrical system (which was mounted upside down as a safety measure against balls and to save space on the robot) - however, I guess we never considered the breakers falling out since we have a hard time pulling them out by hand as it is. But, I guess I can see how this is just another thing we need to consider. Any suggestions on how to guarantee the breakers don't fall out, other than mounting the board right-side up? Has that been a problem with the new Power Distribution Boards?

-Danny

In 2005 we mounted all of our electric upsidedown and we had no problem with fuses falling out. We also used ruber bands to help hold in the PWM cables. This year every thing is mounted upsideright and our fuses have almost fallen out many times. We have to keep checking them and pushing them back in.

[Al Skierkiewicz]

Joe,
Are you using a new PD or last year's?

[joeweber]

Originally Posted by Al Skierkiewicz

Joe,
Are you using a new PD or last year's?

We are using the new one.

I have never seen a game shake up a robot as much as this one.

[Al Skierkiewicz]

That is very odd. Ours is so tight we have a hard time pushing the breakers in. There isn't a chance that the cover has shifted a little and you are inserting the breakers between the cover and the outside of the female terminal is there?
And I know this sounds strange but I have to ask. Have you asked if anyone has made any adjustments to the PD? I have had more than one team stretch open contacts because they thought they were too tight. One was on cable terminals for the Spikes, one was on the old fuse block and one was the main battery connector. The last one produced the most damage.

[joeweber]

Originally Posted by Al Skierkiewicz

That is very odd. Ours is so tight we have a hard time pushing the breakers in. There isn't a chance that the cover has shifted a little and you are inserting the breakers between the cover and the outside of the female terminal is there?
And I know this sounds strange but I have to ask. Have you asked if anyone has made any adjustments to the PD? I have had more than one team stretch open contacts because they thought they were too tight. One was on cable terminals for the Spikes, one was on the old fuse block and one was the main battery connector. The last one produced the most damage.

How I found the loose breakers was in between matches I noticed a light coming form the fuse panel. I chased it down and one fuse was almost completly out and two others were on there way out. The fuses were the 20 amp type. The larger 40 amp fuses were tight and almost impossible to pull out. Maybe it was not pushed in correct but I don't think so.

[Rapt0r9]

We were going to mount all of our electronics upside down, but our electrical captain didn't want to have to lay on his back to work on the wiring, so he just hung panels off of the frame. The biggest problem I would see with a board being upside down isn't the breakers, but the pwm cables coming loose. In the past and even this year, we've had a bunch of issues with loose pwm cables causing control devices to cut out during matches.

This year, the pwm cable for our compressor's spike wouldn't seat into the connector if the spike had its housing on. When I just used the internals from the spike, it responded, but as soon as I put the housing back on the spike, there was no communications between the digital sidecar and the spike. After trying different spikes and different cables, I cut some of the housing for the spike off allowing the cable to sit lower and that was the last we saw of that problem.

[Danny Diaz]

I've been playing with another PD that we have in our shop right now - I have also noticed that the 40-Amp fuses on the new PD are next to impossible to put in and take out, but some 20-amp fuses are easier to pull out and some are waaaay too easy to pull out (I don't remember them being that loose on our robot, and I know none fell out during our pre-ship scrimmage). I'm definitely taking your advice and mounting a plexiglass panel over the PD once we get to Dallas next week, better safe than sorry.

Thanks!
-Danny

[Danny Diaz]

Originally Posted by Rapt0r9

In the past and even this year, we've had a bunch of issues with loose pwm cables causing control devices to cut out during matches.

We used zip-tie mounting plates (1"x1" plastic self-adhesive pads) and forced the PWMs into tension against our Spike and Victors by zip-tying the PWM cables to the mounting plates. The Jags have the tension "clips" that we used to prevent the PWM's from falling out. With this, we cannot even pull the PWMs out by hand without cutting the zip-ties.

Originally Posted by Rapt0r9

This year, the pwm cable for our compressor's spike wouldn't seat into the connector if the spike had its housing on.

You aren't using a male/female adapter on the PWM cable, are you? We find that those male-male (pretty much a 3-pin header almost) adapters do not fit into Victors or Spikes nicely, you've got to use the Universal Servo connector with the pins built into the plug. Otherwise, you have the issue you mention, and it doesn't stay plugged in very long no matter what you do.

-Danny