pic: cRIO CAN Jag

[Daniel_LaFleur]

Originally Posted by Stuart

I just hope that they fixed the issue where if the jags sensed a 6v drop ( for any length of time) it would power down to protect itself( I can replace a bad jag, I cant replace a bad match).

Erm ... power management?

[Gdeaver]

The 2009 game did not stress test the Jag. If First opens up the Can control there are very many issues that come into play with serialized control. With the Can control software pallete there are many ways First Teams could place the Jags into a very stressful situation. It would be nice to Know that the Jags are redesigned and robust before opening up the Can can of worms. The build season is short and the thought of battling controller failures and firmware issues should worry the people who will have to deal with product support. The motor controllers are a key piece to the system. They have to be rugged and reliable. I know everyone wants the Can stuff but, sometimes a conservative roll out can be in everyones best interest.

[Bertman]

Originally Posted by JesseK

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.

"Clear nail polish thing"? please explain.
Thanx

[daltore]

Clear nail polish can be used as a light glue just to hold the connector in place until you want it to come out. Unlike super glue, that last part still works.

Again, if opening up the CAN protocol worries you, use the PWM connector.

[Andrew Schuetze]

Originally Posted by daltore

Again, if opening up the CAN protocol worries you, use the PWM connector.

This last point does need some consistent reminding even for me, more so since I am a veteran mentor since 2001. FIRST has given us options like we've not had before. Tone down the dooms day mentality a bit. There was a day when all we could use was PBasic and items found in the Small Parts Catalog. These are not bad products or vendors at all but when one now looks at the options we have:
Labview, C, Java
PWM, CAN "maybe"
AndyMark.biz, IFI Robotics, BaneBots, FRC Teams operating as LLC ...
Be cautiously prudent or dare to experiment with contingency plans

[Justin Stiltner]

As an additional point of interest:

Keep in mind that your program will need to send the data to a specific address on the CAN bus, so that means that each of your speed controllers will need a unique number... can you guess where this is going?

If you need to replace a speed controller on your can bus, you will need to do one of 2 things, either program your new speed controller with the old ones address, or determine the address of the new one (its not imprinted on it anywhere) and change your code.

Its one of those rock and a hard place problems.

Also, as a network engineer, and working in IT for 8 years now, if you use high quality connectors, and don't abuse them you shouldn't need to worry about those connectors. I have actually seen the cable come apart before the connector came out of the jack in the wall!
However If you buy your cables at the dollar / 50 cent / dumpster store good luck to you!

[Justin Stiltner]

Another separate thought.

The Jaguar controllers have built in PID control, allowing you to command the speed controller to do positive speed, positive positioning, or constant current control of your motors, as well as monitor the current, voltage, temp, etc it is currently outputting, VERY neat stuff... and only available on CAN bus... sign up for CAN bus today!!! Available anywhere CAN supplies are sold!

[R.C.]

Originally Posted by Justin Stiltner

Another separate thought.

The Jaguar controllers have built in PID control, allowing you to command the speed controller to do positive speed, positive positioning, or constant current control of your motors, as well as monitor the current, voltage, temp, etc it is currently outputting, VERY neat stuff... and only available on CAN bus... sign up for CAN bus today!!! Available anywhere CAN supplies are sold!

This is by far one of the coolest posts I've seen in the past few weeks. That should be put on a poster or something.

-RC

[biojae]

Originally Posted by Justin Stiltner

Another separate thought.

The Jaguar controllers have built in PID control, allowing you to command the speed controller to do positive speed, positive positioning, or constant current control of your motors, as well as monitor the current, voltage, temp, etc it is currently outputting, VERY neat stuff... and only available on CAN bus... sign up for CAN bus today!!! Available anywhere CAN supplies are sold!

My first test of the CAN bus will be to make a CIM servo, with PID and a tough box

[Jon236]

Has anyone ordered the Design Kit?

http://www.luminarymicro.com/products/rdk_bdc.html

[DonRotolo]

Originally Posted by squirrel

The signal has to go thru all the connectors in the chain before it gets to the end. If any fail, the signal won't get through to those past it. Is my understanding correct?

Um, yes. I'm not sure what I was thinking, but if one connector fails, everything past that point has failed.

Originally Posted by Gdeaver

The 2009 game did not stress test the Jag. ...

They have to be rugged and reliable.

I beg to differ. The Jaguars were indeed stressed this year - at least by our team - and were found to be rugged and reliable. Please tell us your experiences to the contrary.

Originally Posted by biojae

My first test of the CAN bus will be to make a CIM servo, with PID and a tough box

That would be cool, very cool indeed. You might want to gear it down even further than a toughbox, but we'll cross that bridge when we get to it.

[biojae]

Originally Posted by Don Rotolo

That would be cool, very cool indeed. You might want to gear it down even further than a toughbox, but we'll cross that bridge when we get to it.

At Atlanta, the luminary micro demo of the CAN bus was a wheel on a tough box

it was very neat to see a cim maintain a rate of 10 rpm even under heavy load

[Elgin Clock]

Ok, I'm gonna get some n00b flack on this one, but what exactly am I looking at and how is it different than the setup we had this year??
I see the same components, & only with the addition of a telephone/modem/fax type cable added to the components similar to the way VEX uses to hook up controllers, I don't see much speculation that can come from this?

So... what's the big deal & all the fuss about?
And what the heck is CAN?
Just a little lost over here... I'm mechanical, not electrical! lol

[EricVanWyk]

Originally Posted by Elgin Clock

Ok, I'm gonna get some n00b flack on this one, but what exactly am I looking at and how is it different than the setup we had this year??
I see the same components, & only with the addition of a telephone/modem/fax type cable added to the components similar to the way VEX uses to hook up controllers, I don't see much speculation that can come from this?

So... what's the big deal & all the fuss about?
And what the heck is CAN?
Just a little lost over here... I'm mechanical, not electrical! lol

CAN is a method of communication that allows many devices to talk to each other. Think of it as ethernet, but much simpler.

PWM (as we use it) is a method of communication that allows one device to command another: One piece of information, one direction.

The advantage CAN provides is that more types of information can be sent, and it is bi-directional. This would potentially allow you to:

• Access the Jaguars back-emf and current measuring capabilities.
• Current and voltage control, rather than just duty cycle control.
• Internal PID loops
• Virtual Springs - Combine torque(current) control with built-in quadrature encoder/pot inputs.
• Active load-sharing: Have motors that share a tough-box balance their loads.
• Lots of other cool stuff.

[JesseK]

Originally Posted by Gdeaver

The 2009 game did not stress test the Jag. If First opens up the Can control there are very many issues that come into play with serialized control. With the Can control software pallete there are many ways First Teams could place the Jags into a very stressful situation. It would be nice to Know that the Jags are redesigned and robust before opening up the Can can of worms. The build season is short and the thought of battling controller failures and firmware issues should worry the people who will have to deal with product support. The motor controllers are a key piece to the system. They have to be rugged and reliable. I know everyone wants the Can stuff but, sometimes a conservative roll out can be in everyones best interest.

I don't agree with this, not one bit. This is like asking for the FAA-certified fly-by-wire controllers used on airplanes with the pricetag of a Jag. But hey, that's just my opinion. I've witnessed the beauty of CAN first-hand at some recent demos for work ... in the right situations it fulfills everything we ask it to, almost flawlessly. So here's my over-simplified -isms of the day. If we want to throw rapid current fluctuations and voltages changes through a motor controller that are outside the specs, it's not the manufacturer's fault. Furthermore, no matter how much the programming mentors gloat about it, software control cannot make up for bad power design without significant sacrifice to quality and/or goals.

A more probable -ism is that we shouldn't judge a motor by its size, but rather by the end results of the calculations we produce from it. CAN on!