pic: cRIO CAN Jag

[Andrew Schuetze]

loading photo ...

[Jared Russell]

Very cool. I'm crossing my fingers that this is a "go" for 2010...

[Uberbots]

I like how they just left the head of the cable in the last jag (:

Thats really cool. daisy chained jag's look intimidating without those silly 3-color wires coming out of them.

[Jared Russell]

Does the idea of having (potentially) all of your speed controllers in series scare anybody else?

One would assume that the CAN pass through circuitry is sufficiently removed from the motor driver so that even a "blown" Jag wouldn't bring down the entire network. Even if that is the case it seems like this configuration could lead to a really tough time debugging your electrical system.

[Alan Anderson]

Originally Posted by Uberbots

I like how they just left the head of the cable in the last jag (:

Look at it closely. I'm pretty sure that's a termination resistor, something typically used to suppress signal reflections at the end of a high-speed bus like CAN.

[EricVanWyk]

Originally Posted by Jared341

Does the idea of having (potentially) all of your speed controllers in series scare anybody else?

One would assume that the CAN pass through circuitry is sufficiently removed from the motor driver so that even a "blown" Jag wouldn't bring down the entire network. Even if that is the case it seems like this configuration could lead to a really tough time debugging your electrical system.

Eh, not really. CAN is reasonably fault tolerant. I'd be more afraid of a cable coming out or a device on the bus going "babbling idiot mode" than one Jaguar electrically disabling others.

Originally Posted by Alan Anderson

Look at it closely. I'm pretty sure that's a termination resistor, something typically used to suppress signal reflections at the end of a high-speed bus like CAN.

Quoted for Truth. Standard CAN usually has 120 Ohm termination resistors on either end of the bus.

[MrForbes]

THe only thing that worries me is all those RJ45 connectors in series.....you saw what happened to similar connectors on the DS this year when used in a competitive environment.

[Nick Lawrence]

Originally Posted by squirrel

THe only thing that worries me is all those RJ45 connectors in series.....you saw what happened to similar connectors on the DS this year when used in a competitive environment.

Well, ideally your electronics would be in a low impact area on your robot, right?

-Nick

[MrForbes]

Yeah, right

[JesseK]

Originally Posted by Nick Lawrence

Well, ideally your electronics would be in a low impact area on your robot, right?

-Nick

Finding a low impact area is difficult to do in the situation where a 150lb robot going 12fps slams into your bot.

If anything we can do the clear nail polish thing again. It worked wonders on the IFI PWMs and it still works great on my R/C car.

[MrForbes]

Unfortunately the RJ series connectors are inherently flaky....

[EricVanWyk]

Originally Posted by squirrel

Unfortunately the RJ series connectors are inherently flaky....

Please don't assume that because KwikByte chose to use an unacceptably inferior component that TI/Luminary did as well. RJ connectors come in many forms and many quality levels. If you squeeze cost out hard enough, any component can become a failure point.

[R.C.]

In my opinion, I hope they release the module before season so we have a few week to play with it. Even though none of our pwm's ever came out, I personally would feel better if we used CAN.

-RC

[Andrew Schuetze]

What I like about CAN is removal of several PWM wires all traveling the same path and having to check which pin number it was in and verifying correct orientation on both ends several times during the build when things would get disassembled and reassembled. With CAN, 1 RJ45 cable from the cRIO from just the CAN bumper to the first device and then daisy chain from there. No need to verify orientation and keep the log of which pin to which device ... all that is in the code and addressing log.

How many times did your robot temporarily lose functionality after a re-build because a PWM was not inserted into the correct pin ...

[MrForbes]

Originally Posted by EricVanWyk

RJ connectors come in many forms and many quality levels. If you squeeze cost out hard enough, any component can become a failure point.

Unfortunately, cost seems to be the primary design consideration for the RJ series since it's inception decades ago.

Hopefully Luminary has figured out how to make the system reliable....but my long experience with the connector series isn't good.