Victor-PWM Cable connections

[RbtGal1351]

Hello all,

I am wondering what fixes teams have come up with to ensure a good connection between the Victor Speed Controllers and its PWM Cable.

What happened: During the final rounds at Davis, one of our drive motor Victors started continually blinking orange (no signal). We traced the problem to a bad PWM cable connection. We did replace a fried Victor right before this problem occurred, so I would assume that our cables were just unseated during this process. We did, after this, make sure the PWM cables were plugged all the way in, which they were. I am wondering how the PWM cable does not make contact if it is all the way down (vertically).

Also, our victors are mounted on the bottom of our robot, so it would be rather unlikely for the cable to just "pop out" of the Victor seating, plus they are electrical taped in to avoid this very problem.

If the connections are so precarious to unseat and lose the connection that easily, how and why do they withstand competitive matches? Or don't they?

What have you come up with to solve this problem?

Thanks a bunch in advance,
~Stephanie

PS--Searched, these threads may be useful too:
http://www.chiefdelphi.com/forums/sh...m+connec tion
http://www.chiefdelphi.com/forums/sh...m+connec tion

[mtaman02]

I don't know how much help this may be but here it goes, This problem has been around for the past few years and well there's really not a whole lot you can do about it, when I first joined in 2002 the Speed Controllers had a slight design change then what they are now which was the cable would just sit in the speed controller which was a major headache because then the cable could wiggle freely about. After I think '02 or '03 IFI revised the speed controllers so that they would have a small rectangular piece around the area the cable goes in. While this solved the problem of the cable moving freely about, a new problem came up and that was you could never tell if the plug was all the way in or lined up with the holes.

Now as for a solution maybe there will be another revision to the speed controller for '07 depending on how many teams let IFI know of the problem of the PWM Cable being plugged into the speed controller.If teams don't let IFI know of this problem at the competitions or if they don't email or call IFI then nothing will get resolved.

The only solution(s) that I can think of right now:
1) Leave the robot powered on and communicating and reseat the cable till the speed controller has a solid amber light that way you won't have to guess if the wire is in all the way or if all the pins are in the holes and you can see the status of the speed controller as your doing it, after that find away to hold the cable in place so that it doesn't pop out.
2) Is if IFI makes the speed controller in a way that when you plug the cable in it snaps into place ensuring that the cable is secured correctly and is lined up with the holes.

[Mike Martus]

There is a device that is sold at one of the Robot parts sites like
"Robot Marketplace"

http://www.robotcombat.com/marketplace

that is a PWM clip. They keep down pressure on the wire. This clip takes space and will require access to the speed controller.

I am not seeing the part but am sure this was the site.

[KTorak]

Correct link.

[DonRotolo]

Originally Posted by RbtGal1351

I am wondering what fixes teams have come up with to ensure a good connection between the Victor Speed Controllers and its PWM Cable.

How about the other end: We had some issues with the PWM cables popping out of the RC. The way we mounted the RC it was difficult to see, leading to some puzzling moments...

Does anyone have a good way of keeing the cables on to the RC, aside from hot melt glue (which, in my experience, eventually comes loose)?

Don

[Billfred]

I haven't tested this, and as such I'm not making any warranties, but what about a thin bar that goes through all of the PWM cables just above the connector and keeps the RC connection from being pulled up accidentally? (I'm imagining something like the gates to the FRC field, except the other end would unlatch as well.)

[lukevanoort]

I never had this problem this year, although I was told by the guy who wired last year's 'bot that he had this problem and I should be careful. So, I looked at the board differences, and the only major difference I can see is this year's has less distance to the controllers from the RC and there is zero stress. The whole setup is also mounted at a 90 degree angle to the floor as opposed to flat as in last year's I don't know if that helped it or not...

[Josh Hambright]

An old fix that i can remember using on the old victor with the old style of PWM connector was to put a small dab of hot glue on the connector, this can also be done on the other end where they all connect to the RC. Using hot glue makes them stay in place but you can peel it off if you need to remove the connections.

[RbtGal1351]

Originally Posted by Don Rotolo

Does anyone have a good way of keeing the cables on to the RC, aside from hot melt glue (which, in my experience, eventually comes loose)?

We electrical taped our PWMs to the RC, and our RC was at a 45 degree angle facing down, and had no problems.
(But I can't guarantee that this will work, seeing as our Victor PWMs were electrical taped and they were mounted right side up... )

Originally Posted by KTorak

Correct link
.

How does this help?

Thanks
~Stephanie

[lukevanoort]

Originally Posted by RbtGal1351

How does this help?

I think he means this. About 2/3s of the way down, they clip on and hold the PWM.

[KTorak]

Originally Posted by lukevanoort

I think he means this. About 2/3s of the way down, they clip on and hold the PWM.

Sorry about that. I know I navigated to the right page with the item...but it must not have copied it.

[Gary Bonner]

We had some cables/Victors that would not consistently make contact even though the cables were seated all the way down. We very slightly bent the middle pin so that the three pins were not exactly in a straight line. This seemed to take care of the problem.

[eugenebrooks]

Originally Posted by RbtGal1351

Hello all,

I am wondering what fixes teams have come up with to ensure a good connection between the Victor Speed Controllers and its PWM Cable.

The wadded up extra length of the pwm cable can present an extra
bit of mass that wiggles the cable when the robot moves. We cut
our PWM cables to the required length, replacing the female end with
a Molex C-grid connector, using the "high force" sockets. We don't
use the C-grid connector on the male end, the pins seem to be too
short to make a good connection to the victor/spike.

The cable itself is zip tied to the electronics board right next to the
controller, or the victor, so that the cable comes up and over with a
inverted U shape, providing for stress relieve in the event of impact.
Attaching the electronics so that the force of typical impacts is
perpendicular to the connector, removing the tendency of the impact
to pop it out, is a good idea.

We check all of these connectors between every match to make sure
that none are walking off, and we keep track of any that might be
moving. If it moves a half millimeter when you push a little with your
fingernail, it is walking off and you need to do something about it.

There is no substitute for checking the connectors between every match,
and laying out the electronics to make it easy to do this without bumping
wires, but you can take measures to improve things:

* You can make a bracket that pins the connectors down when
it is screwed to the electronics board. With due attention to the
possibility of a short, the 3 dollar clip available at robot marketplace
would seem to work for a victor, but you need a single bracket to
hold a large number of connectors on the RC. I would want these
brackets to be made of plastic to reduce the chance of a short,
but the aluminum ones on our robot this year were insulated
with electrical tape. If you have th luxury of using every other
PWM output on the controller, you can make a "comb" style of
bracket that will hold the connectors better.

* Another strategy is to glue the female connectors to each other
as you install them on the RC, producing a single connector with
a large pin count. The resulting high pin count connector is almost
impossible to walk off, although you can get if off if you need to.
The drawback here is that if you need to replace one cable for some
reason you get to do some cutting, but it produces a connector that
does not walk off without using a bracket. We use this strategy for
the array of switches used to provide autonomous modes, or inhibit
motors for safety in the pits, that are connected with a single multi-
conductor cable.

[Rickertsen2]

Overall, PWM cables seem to be the #1 source of electrical system problems. .1" headers are NOT designed for this type of application. They are however the standard for RC control. I prey that they will change during the next IFI design cycle.

As far as fixes, our team hot glues all of our pwm cables in place. Hot glue holds well enough to keep them where they belong, but also breaks away cleanly if you ever need to change something. We also use electrical tape to make a single connector our of the RC side connections.

[ECarlson]

Originally Posted by lukevanoort

I think he means this. About 2/3s of the way down, they clip on and hold the PWM.

Those look like a good idea, unless the metal cuts into the cable, or shorts out something else, but you should be able to avoid those problems.

One thing we did on the RC side, at least for our sensor connectors, was use one large connector block to hold all the wires, so it's easier to hold in place.

BTW: Here is the image from the robotcombat web site of the Victor PWM Clips: