Problems With The Power Distribution Block [Archive]

sanddrag

26-03-2007, 00:57

I'm sorry, but that Rockwell Disribution block has just GOT to go, or at least not be made mandatory. I'm sure it is a fine product, but just not in this application. For the sake of Rockwell's good name, I think it needs to keep it's home in its intended application. Bare wires screwed into terminals just doesn't work in FIRST. And the size and weight doesn't either. I inspected at two regionals. I couldn't find any team that was glad to have it. Most teams expressed their frustration with being required to use it.

Additionally, my team experienced the wires continually loosening and falling out of it, and the electrical engineers on the team also express their concerns with this item in the kit of parts.

So, for everyone else replying to this thread, I know you don't like the thing. But, please state the specific problems it has caused for you.

Tom Bottiglieri

26-03-2007, 01:03

One of the screws in the center coupler (little yellow thing) of the ground distribution wiggled loose during competition. Well, apparently when we started pushing the bot to its limit, a spark gap was created between the coupler and the block, causing both to melt. No fun.

Steve W

26-03-2007, 01:06

Everyone knew about this issue a while ago. A little Loctite will fix the problem.

Tom Bottiglieri

26-03-2007, 01:08

Everyone knew about this issue a while ago. A little Loctite will fix the problem.
Everyone? I'm pretty sure I didnt. And what about the rooks who don't even know what Loctite is?

sanddrag

26-03-2007, 01:35

I thought loctite ate plastic, so, I didn't go for it. Is this a different type of plastic that it doesn't eat?

Greg Marra

26-03-2007, 01:39

While we're talking about electrical stuff...

I am a big fan of the 2005 Power Distribution Block Thing made by IFI. I would love to see them return to bring simplicity back to robots' electrical systems. I helped wire two rookie robots in the pits at Boston on Thursday, and having that single block would have made things easier, and simpler for the rookie teams to understand.

RoyalRobo1070

26-03-2007, 02:53

Our main problem with it was one that was already pointed out: that the wires continued to slip out, as tightly as I or any other member or mentor screwed the screw in. If FIRST intends to continue with this power distribution block, I would suggest that they give us tips on how to keep those wires in.

allen_d

26-03-2007, 03:16

Everyone knew about this issue a while ago. A little Loctite will fix the problem.

Do they make a dip tank full of loctite that we can submerge our whole robot in?

I was not aware of this problem. I don't recall this being in any of the team updates.

I get a little concerned using loctite for this application. Even though we use blue loctite... we someday might need to take this apart!

Daniel_LaFleur

26-03-2007, 07:01

Everyone knew about this issue a while ago. A little Loctite will fix the problem.

First off, you should avoid using absolutes like "everyone knew", because, invariably, someone does not know.

Secondly, be very careful about reccomending loctite. Know your application and the type of loctite so that you can guage the reaction. Test on a sample (NOT ON THE ROBOT) to ensure compatability.

*note* I believe that Loctite is a good idea for this application, but please make sure that the type of loctite you use is compatable with the plastics and vynal wire coverings.

Pavan Dave

26-03-2007, 07:06

At Bayou, we checked our wires on and we ended up putting in some Loctite. I was against it, but after a mentor showed me how loose some of the wires were I said anything was better than nothing, and so we gave it a go. Well, none of the wires popped out to my knowledge and the drive team didn't have to tighten them after we put in the Loctite so I was satisfied. It works...but I'll get to do a better electrical inspection come Thursday at Lone Star and be even more sure!

Do I see it as necessary? No, but FIRST has their reasons I assume and now I know about ferrules and have all summer to think of new ways to keep wires in! Make this your off season project if you don't have one and than you won't have to worry about how to make wires stay in tight next year.

Pavan.

mtaman02

26-03-2007, 07:16

While we're talking about electrical stuff...

I am a big fan of the 2005 Power Distribution Block Thing made by IFI. I would love to see them return to bring simplicity back to robots' electrical systems.

I inquired about the Power Distribution block at the NYC Regional and if it will it ever make a comeback the answer coming from the horses mouth (IFI) was most probably not due to the loss of money in making the product (not enough buying the product retail wise) they do agree that it was a well crafted product that made wiring a robot simple it just cost too much to manufacture it and have no one buy it.

And I know there are plenty other threads concerning this but while I already went off the topic already for all those who are wondering if the RC will change - Also coming from the horses mouth (IFI) more than likely......... not. They are happy with its current size and dimensions and why change something that works perfectly. However when ever the ancient DB9 Port is completely extinct then start looking for a new RC configuration but until then don't hold your breath =).

While Loctite is a good answer to keeping almost any screw in place I would not use a whole lot of it b/c like many have said it will need to be taken apart someday. I'm pretty sure they're other solutions out there. Maybe instead of using Loctite do some test with some crazy glue. While it's not strong enough as loctite it should get the job done and be able to be undone with just a little bit of heat.

Alan Anderson

26-03-2007, 08:23

Everyone knew about this issue a while ago. A little Loctite will fix the problem.

Loctite on the yellow jumper's screws might be okay, but don't use Loctite it on screws holding wires in place. The wires will loosen with time (and vibration), and you will want to tighten the screws regularly.

I don't mind the Rockwell block. If properly installed, it serves its purpose well. The only big problems I've seen teams have with it are due to misunderstanding how the wires get clamped in.

After using the DIN rail this year, I've been playing with the possibility of adapting the Spikes and Victors to be DIN-mountable as well.

Steve W

26-03-2007, 08:34

First off, you should avoid using absolutes like "everyone knew", because, invariably, someone does not know.

Secondly, be very careful about reccomending loctite. Know your application and the type of loctite so that you can guage the reaction. Test on a sample (NOT ON THE ROBOT) to ensure compatability.

*note* I believe that Loctite is a good idea for this application, but please make sure that the type of loctite you use is compatable with the plastics and vynal wire coverings.

You are correct. Maybe not everybody knew but then not everybody reads the rules, updates and email blasts. I will be more careful on my wording in the future. FYI from update #14

"We would like to remind teams that the Allen-Bradley terminal blocks are required per the
Power Distribution Diagram. If you did not put them on your robot please be sure to bring
them with you to your events. Furthermore, we’ve gotten feedback that the screws may
become loose with vibration. We recommend that you periodically re-tighten the screw
terminals to prevent any connectivity issues." (I added the color and bold type)

Purple loctite seems to work well but does not make it difficult to undo or re tighten.

underwood

26-03-2007, 12:42

seems to me the solution is simple: rivet the friggin wires in!!:yikes:

(i'm being funny, but over-the-top solutions like this are usually neccessary. I hate this darn block:( )

MrForbes

26-03-2007, 12:58

We didn't have any trouble with the block at our first regional

I wonder if the problems with wires coming loose has to do with the mounting and routing of wiring? if the wires can't wiggle around, they most likely won't come loose....

I can see how it would be a good idea to check the tightness of the wire clamp screws occasionally, and to make sure the jumper screws are tight before a regional. I can't see how it would be a good idea to use loctite on the power distribution block.

Brandon Holley

26-03-2007, 14:15

At the winter warzone we had all kinds of problems with the block arc-ing and causing our victors to short out. It cost us the quarterfinals there.

seanl

26-03-2007, 18:39

the block is not totally useless. it seves a good purpose, it just has a few "bugs". i agree that it could be a bit lighter, but i dont really mind it. the only problem we had with it was that the main ground wire got pulled out by a divetrain person accidentally tugging on it, which was easily fixed with a screwdriver. overall i dont really care about the block. i just hope FIRST fixes the bugs in the block if they are going to implement it in next years game.

CraigHickman

26-03-2007, 19:23

For other purposes, the block would be amazing. For example, I plan to buy one for a project I'll be doing in my room. It'll be great for that, as I need breaker panels all over the place. However, on a vibrating, moving, slamming robot with only two breaker panels, it's practically useless.

We never had any problems (yet) with the block. One idea we had to meet the rules was to drill holes straight through the block from wire point to wire point, and run the normal wires through the holes. However, we ended up deciding to just wire the thing up in the required manner.

Al Skierkiewicz

27-03-2007, 08:29

At the winter warzone we had all kinds of problems with the block arc-ing and causing our victors to short out. It cost us the quarterfinals there.

At 12 volts these blocks cannot arc. Intermittant wiring will cause heating and intermittant electrical power can cause problems with any electronics. All termination devices at normal robot currents will have these problems including the interface to the battery terminals.
The Rockwell blocks use quasi-parallel clamps to secure the wires. If a wire is not stripped back enough or if the wire is not inserted far enough, the clamp will squeeze/push the wire out of the terminal. If you take a look at the picture (thank you to the Rockwell site) you will see that a wire that is not inserted to the end of the clamp will loosen and fall out. The specification from the Rockwell Catalog for this series (1492-J16) is "Wire Strip Length 0.63 in (16 mm)". The molded-in wire stop correctly positions the wire in the jaws for best termination. Additionally, stranded wire will be forced to change cross section as the clamp pushes down on the wire. This may force teams to check the tightness from time to time. (robot movement will shake wires and make this worse) For these reasons, Loctite is a bad idea on these blocks.
Some folks have suggested the use of ferrules over the wire. Debate is still raging but i have some Panduit samples coming in the next week or so to look over. stand by...

Danny Diaz

27-03-2007, 11:44

At Bayou, we checked our wires on and we ended up putting in some Loctite. I was against it, but after a mentor showed me how loose some of the wires were I said anything was better than nothing, and so we gave it a go. Well, none of the wires popped out to my knowledge and the drive team didn't have to tighten them after we put in the Loctite so I was satisfied. It works...but I'll get to do a better electrical inspection come Thursday at Lone Star and be even more sure!

I'll see about getting you a, "But it works on our robot!" sticker. We've had mountains of problems with wires coming loose during the build season, so we've instituted wire tightening/inspection specifically for the block in our pre and post match checklist.

-Danny

Hieb

27-03-2007, 12:00

MrForbes

27-03-2007, 12:06

The spec sheet for the terminal blocks suggests tightening the screws that hold the wires in, to 17 to 35 lb-in torque. That's a lot of torque to apply with a slot screwdriver! Maybe what's needed is to make sure someone with strong hands tightens the connections.

Also double check the wires are stripped the minimum 5/8" length.

Having a checklist to double check the tightness of the screws before competition, is a good idea.

Al Skierkiewicz

27-03-2007, 12:06

Alan Anderson

27-03-2007, 13:16

I know that some manufacturers of similar power distribution blocks (not sure about Rockwell--I haven't spent enough time looking) have spring loaded connectors that may be more suitable for our applications. At least that way the vibration wouldn't loosen the screws and let the wires fall out.

The problem isn't usually with the screws themselves loosening. It's almost always because the stranded copper wire deforms and is no longer held tightly. This can happen not only with the Rockwell parts, but with the 40-amp fuse block as well.

Make tightening the electrical connections part of your standard preventive maintenance and pre-match checks, just like keeping proper chain tension or making sure the pneumatic release valve is closed.

eugenebrooks

27-03-2007, 21:19

I am not enamored with the rockwell power distribution block.
The positive end of the block is completely redundant, one can
simply route the positive wire through the max-fuse block to
the panel for smaller fuses and be done with it. We can do
a much lower resistance job for the ground returns with the
ground lug from 2004 than we could ever get from the power
distribution block.

Loctite should not be used on electrical connections, it is not
a conductor. There is no substitute for proper torque on all
of the electrical screws, and proper stress relief for the wires.

The terminal block does need to be tightened to specifications.
If you don't have a suitable torque screwdriver, you can do quite
well with a wrench attached to a hex drive screw driver, and a
small "fishing scale."

We have not had problems with bare wire in the power distribution block,
but if we have to use this distribution block next year we will certainly
use the ferrules.

Eugene

T3_1565

27-03-2007, 21:43

All we did was put solder on the wires to stop them from fraying apart, which seemed to be our problem with why they were slipping out. Anyone tried that?

Al Skierkiewicz

27-03-2007, 23:11

All we did was put solder on the wires to stop them from fraying apart, which seemed to be our problem with why they were slipping out. Anyone tried that?

T3,
Tinning wire before insertion into a clamp type terminal should not be used. It prevents the wire strands from compressing inside and providing maximum contact area with the terminal. A tinned, stranded wire will act like a solid wire in most cases, usually making the problem worse and raising the series resistance.