Re: Looking for a connector
 

I did screw terminals last year, only problem is that there isnt really a quick way to disconnect the control box.

Re: Looking for a connector
 

Were you using the 45A contacts? Which motor were you using?

Re: Looking for a connector
 

Read the data sheet I provided the link too. 45A rating is the continuous duty, which for this connector is considered more than 1 minute, only when they are in a single configuration with 10ga wire.

Stack them together and the continuous duty rating drops way down.

I realize many teams "have gotten away with it" however one of the concepts of first is to encourage good, safe design practice. Using a connector rated for ~30A in a circuit that uses a 40A circuit protection device is not good, nor safe design.

Re: Looking for a connector
 

I think that's debatable....

Defining the requirements well is part of the design process. One of the requirements is that the robot last thru several 2:15 minute matches. That's quite different than most commercial products.

Re: Looking for a connector
 

Lets also keep in mind that most robots won't be sending 30+ A to a motor for more than a minute. Your CIM motors will get that high when you're starting from a stop, or when you're pushing against something, but those are typically relatively short moments. Most of the match, your drive train will be pulling somewhere in the teens, if not lower. As for the other motors... even the FP we had powering our elevator last year wasn't pulling 30 A throughout the match... and it was either stalled or moving pretty much the entire time (and we had some serious binding issues in the elevator).

Re: Looking for a connector
 

I agree that we are designing a robot to only last for an hour or two of total run time.

However good, safe, electrical practice dictates that in circuit design the minimum rated component in the circuit is rated at least as high as the circuit protection device, otherwise the circuit protection device can't protect the circuit.

Re: Looking for a connector
 

Mr. V,
In the paper you have linked to it is important to note that curves are only annotated to a 40 degree C rise. The UL rating for these connectors is based on a 65 degree rise. Of more interest is the pulsed current ratings for multipole connectors based on this standard. Note that with a #10 wire, the safe current is more than double the rated current when applied for less than two seconds at a time. Further derating can be included for connectors that are in the open rather than part of an assembly. For the majority of teams using these contacts for CIM motors with #12 wire for all power wiring, the series resistance of the wire, the battery, the speed controller and the contacts will limit the overall current to right around 100 amps in stall.

Re: Looking for a connector
 

Can someone explain to me how/why the connectors behave so differently with different gauge wires? The contacts are always the same as is the contact between them. The only thing that can change is the contact area between the wire and connector but that surface area is much larger than any other surface on the contact. If the gauge of the wire makes such a big difference, soldering the wire in should make an even bigger difference.

Re: Looking for a connector
 

Jason,
The rating is a direct result of heat rise in the contact. With larger wire, more heat is transferred away from the contact by the wire. It is essentially acting as a heatsink. Solder will only affect the heat rise if a crimp was made improperly and the wire is loose in the contact. The higher resistance will produce more heat. Dirty contacts, bent and misaligned or scratched contacts likewise will have higher heat associated with them.

Re: Looking for a connector
 

You guys mentioned using Anderson connectors...

My team has also been using them every year I have worked on our robot. If you're looking for a kit to get you started with using them, check this out:

https://www.base2.us/index.php?page=...de=b2kit-appk1

Re: Looking for a connector
 

Al,

They are not UL rated for a 65 degree Celsius rise they are UL rated for a 45a current at a maximum of 65 degree Celsius.

That is why the graphs only go to a 40 degree Celsius rise because they are basing it on a rise from ambient temp which the industry standard is 25 degrees Celsius. (25 C = 77 F for those of us that aren't that familiar with Celsius)

Using the pulsed current ratings are not really suitable in this case. Certainly they could and usually will see pulsed current in a FRC application but they could also see continuous current or pulses that last for more than a few seconds. As such the design should account for the worst cast scenario so the continuous ratings graphs are applicable.

As I previously stated, yes teams have shown that they "can get away with it", but 1 poster in this thread has indicated that they did indeed fail in a stall situation.

Re: Looking for a connector
 

Mr. V,
You are correct in that it is not a 65 degree rise specification. What the 65 degrees refers to is the UL standard of maximum current based on 65 degrees measured at the contact. This temperature is chosen as the reference point based on the failure temperature of the plastic body less some derating for safety. The connector can withstand continuous 45 amps forever under this test. I believe that the pulsed data is relevant for this connector based on general use in FRC robots and the addition of the circuit breakers that are in place. I cannot comment on the reported failure earlier in this thread. There are a number of factors that could have contributed to the failure beyond simply current.