CAN Rules

[duane]

And while I'm at it, do teams have any recommendations for connectors for the CAN wires?

We are likely to try out the new Talon SRX. They have wires for CAN. How should We connect the CAN wires together? What kind of connector would be good here?

We're considering PWM connectors, but they PWM connector notoriously do not lock.

Thanks for the ideas.

[Peter Johnson]

Originally Posted by duane

And while I'm at it, do teams have any recommendations for connectors for the CAN wires?

We are likely to try out the new Talon SRX. They have wires for CAN. How should We connect the CAN wires together? What kind of connector would be good here?

We're considering PWM connectors, but they PWM connector notoriously do not lock.

Posted this in another thread, but since you ask.. Hansen Hobbies sells 2-pin latching polarized PWM connectors. They are what we'll be using on our 2015 robot. http://www.hansenhobbies.com/product...nlpconnectors/

[NabilHanke]

The connectors form Hansen Hobbies are at a price premium. They are just Molex connectors - try digikey http://www.digikey.com/product-detai...2573-ND/134131

Also, electricity is color blind to insulation color. Twisting your pairs isn't absolutely critical on CAN, but not doing so will turn 2 minutes of laziness into two hours of hair pulling. CAN uses a differential signal: both will rest to the same voltage, then when signaling, CAN High gets pulled up a volt or two and CAN low gets pulled down a volt or two and they are compared against each other. If there is noise it'll effect them the same and that differential will remain intact. Good stuff.

Where you can find another opportunity to pull your hair out is loose connections on the CAN bus. It is a bus, all CAN High connections should be congruent with each other and all CAN Low connections likewise. If you have a bad connection in the middle, you'll lose not just the other half of devices, but the terminating resistor as well and the whole bus itself... well, in an ideal world. But fortunately theory and reality don't agree and sometimes you'll still have an intact bus.

BTW, I'd use WAGO lever locks for the motor controllers.

[ozrien]

Originally Posted by NabilHanke

Also, electricity is color blind to insulation color.

Yeah, the green/yellow is helpful for other reasons.
-Makes robot inspection and troubleshooting easier.
-The colors are labeled on the roboRIO CAN connector
-The colors are present on the PDP/PCM Weidmuller connectors.
-The colors match the Talon SRX cable harness
It all adds up to a better CAN bus experience.

Originally Posted by NabilHanke

Twisting your pairs isn't absolutely critical on CAN, but not doing so will turn 2 minutes of laziness into two hours of hair pulling.

Very well put.

[nighterfighter]

Originally Posted by duane

And while I'm at it, do teams have any recommendations for connectors for the CAN wires?

What we did (temporarily) is just twist the ends together, then wrap with electrical tape. It lets you verify everything works, you can address each Talon, and drive it around.

[cglrcng]

Originally Posted by stinglikeabee

If you want to twist your own cable...

https://www.youtube.com/watch?v=YAquFszYZ1k#t=75

Note: Please do NOT FORGET YOUR SAFETY GLASSES like the guys in the video did if twisting that wire w/ a drill. Sight is important!