Gluing PWM connectors into Motor Controllers

[feverittm]

I was talking to another one of our mentors the other day and he told me something interesting.

I have always (past 4 years of FIRST electrical) that it is a good idea to put a drop of hot melt glue on your PWM connections on the motor controllers to keep them from falling out. This is especially true for older Victor style controllers whose connections can become loose.

However, he told me that 'gluing' the PWM connectors is illegal as it counts as 'modifying' the controller.

Does anyone know for sure? I wanted to make sure before we decided to follow this strategy and maybe make a mistake.

Thanks

[joelg236]

I've seen discussion of this before. Most people agree that it is technically illegal, but depending on the inspector may or may not get looked at.

We did it last year at 3 competitions, never had an issue.

[Nirvash]

I would agree that it is technically illegal. However if one follows that rule that strictly, it would probably also disallow labels, Velcro and anything else that uses adhesive to bond to the motor controller.
In my opinion, it is an example of taking a rule too literally.

[billbo911]

We do this on a regular basis with both 884 Victors and Spike relays. Not once has an inspector had an issue with it.

Honestly, I can't even imagine why it would be an issue or even be considered modifying a speed controller any more than using thread locking compound on a motor mounting screw is modifying the motor.

[jspatz1]

Ah, the semi-annual PWM-gluing thread.

Its not really an uncertain matter of opinion whether or not gluing is considered tampering with a motor controller. R65 specifically states that gluing is prohibited on a motor controller. Its a dumb rule, but its a clearly stated dumb rule.

[cbale2000]

The nice thing about using hot glue, whether you believe its legal or not, is that it can be easily removed if an inspector has a problem with it.

[billbo911]

Originally Posted by jspatz1

Ah, the semi-annual PWM-gluing thread.

Its not really an uncertain matter of opinion whether or not gluing is considered tampering with a motor controller. R65 specifically states that gluing is prohibited on a motor controller. Its a dumb rule, but its a clearly stated dumb rule.

Jeff,
Thank you! Whether I agree with the rule or not, it is a rule, and I was unaware of it. There is no one to blame for that but me. Time to change our practices.

Originally Posted by cbale2000

The nice thing about using hot glue, whether you believe its legal or not, is that it can be easily removed if an inspector has a problem with it.

Agreed!
That said, it is a hard and fast rule. So, if it is still in place this coming season, we WILL follow it.

[Pault]

Remember the standard disclaimer that the rule could possibly change next year. And this is one case where that really should happen (at least put in a blue box beneath the rule creating an exception for this).

[thefro526]

For what it's worth, here's the rule (2013 Manual) that's being cited as preventing hot glue from being used to secure PWM connectors to speed controllers.

Originally Posted by 2013 Game Manual

4.1.9.11 R65
The Driver Station software, cRIO, motor controllers, relay modules, wireless bridge, and batteries shall not be
tampered with, modified, or adjusted in any way (tampering includes drilling, cutting, machining, gluing, rewiring,
disassembling, etc.), with the following exceptions:

A. User programmable code in the cRIO may be customized.
B. Dip switches on the cRIO may be set (applies to cRIO-FRC only).
C. Motor controllers may be calibrated as described in owner's manuals.
D. Fans may be attached to motor controllers and may be powered from the power input terminals.
E. If powering the compressor, the fuse on a Spike H-Bridge Relay may be replaced with a 20A Snap-Action
circuit breaker.
F. Wires, cables, and signal lines may be connected via the standard connection points provided on the devices.
G. Fasteners may be used to attach the device to the OPERATOR CONSOLE or ROBOT.
H. Labeling may be applied to indicate device purpose, connectivity, functional performance, etc.
I. Brake/Coast jumpers on motor controllers may be changed from their default location.
J. Limit switch jumpers may be removed from a Jaguar motor controller and a custom limit switch circuit may be
substituted.
K. If CAN-bus functionality is used, the Jaguar firmware must be updated as required by FIRST (see Rule R68-D).
L. The First Touch I/O module’s firmware may be modified.
M. Devices may be repaired, provided the performance and specifications of the component after the repair are
identical to those before the repair.

If you read the rule in it's black and white context, speed controllers are not allowed to be modified other than the above exceptions. (Fans, Connect Wires to/from, Labeling, etc.)

Depending on how you interpret the rule, arguments can be made on both sides for why hot-gluing the PWM cable is legal or not legal.

On one hand, you can argue that the speed controller is not being modified, as it still performs and functions the same as a commercial off the shelf unit, with the only real change being that the PWM cable will not come unplugged at random. (And you are allowed to connect PWM cables to the controller per R56.F)

On the other hand, it could be argued that if the hot glue were to remain on the speed controller after the PWM cable is removed (it happens) then the speed controller has now been modified. The hot glue could also be interpreted as making the 'standard connection' a 'non-standard connection', depending on the inspector.

I guess if someone really wanted to stretch things a bit, one could argue that if the PWM cable comes unplugged during operation, then the speed controller is not functioning as intended, and is therefore in need of repair. Since the speed controller is designed to retain a PWM cable under normal operating conditions, a dab of hot glue on the connector would allow the speed controller to be restored to it's intended function. (Although, it could be argued as being different in function than a COTS unit, depends on the inspector.)

In any case, in my 8-ish seasons of doing FRC, I can't remember a single instance of an inspector giving us a hard time about hot gluing the PWM's into the speed controllers - heck, some have even suggested it. If you decide to go through and apply hot glue to the connections in the coming season, make sure that you re-read the rules, and see if they've changed at all. If they don't, be aware that you may have to remove the hot glue down the road, and if you're told to do so, to just go with it.

[Alan Anderson]

Originally Posted by thefro526

On one hand, you can argue that the speed controller is not being modified,...

Unfortunately, the "gluing" restriction falls under the category of tampering, so any argument about modifications is not relevant.

[DonRotolo]

We have used a substance a lot like modeling clay* to hold the PWM cables on a Victor in place (back when we used Victors). We never had a problem with inspections, and it isn't gluing, nor is it permanent, so it does not appear to be tampering (no more than using a label to mark the Victor, for example).


*I think it is the stuff used to hold fine china and vases down to a shelf so it doesn't fall over. Museum putty?

[AlexH]

http://www.loctiteproducts.com/p/cnt...ting-Putty.htm

this stuff?