Re: New Talon Speed Controller
 

Darn, I was planning on doing a test like this later this fall (I was waiting for the new Victor)! When the new Victor comes out, can you add results from its performance and let us know here? I'd be very interested to see how it compares.

The Talon definitely looks good!

Re: New Talon Speed Controller
 

You really need to have some form of inductive load on an h-bridge to measure its linearity. The current gen Victors are very non-linear, but your measurement technique significantly over-states this.

Essentially, for a given bridge frequency and rectification style there is inductance * average current combination above which the bridge is nicely linear. Below that threshold, you will see weird non-linearities that are highly dependent on the specific motor and amount of current flowing. Above that threshold, it is close enough to "perfectly" linear.

Re: New Talon Speed Controller
 

Guys:

Read the fine print. That's open-circuit voltage linearity.

When connected to a loaded motor, the Vic 884 is much more linear.

Re: New Talon Speed Controller
 

Yup, that's why I said a test like it, not the exact same test :p I've actually been talking with one of our mechanical mentors for the past 10 minutes about how we could best do a simulated load to repeat this testing with our team... We were thinking of putting two CIMs into a gearbox, and setting one of them to Brake (sending it a 0 signal), while trying to drive the other one. Any better ideas out there?

Re: New Talon Speed Controller
 

If you can get your hands on a big programmable DC load, connect the second CIM to that and you can then vary the load on the drive motor across a wide range. Finishing building mine has been on the "list of stuff that never gets done" for a while now.

You also can just put big various power resistors on the second CIM. We used to call them "toasters" in the motor lab.

Re: New Talon Speed Controller
 

For anyone thinking about doing similar testing this offseason, I would recommend using the PWM class rather then the Jaguar/Victor Class. This removes any bias from scaling built into the Jaguar/Victor Classes.

Re: New Talon Speed Controller
 

Or use this.

Re: New Talon Speed Controller
 

Joe - This is a rather interesting point. Using the PWM class would allow you to more accurately evaluate the speed controllers in a "stand-alone" fashion. However, that doesn't represent real-world (maybe FIRST-world is a better term?) use. When we use the speed controllers, we use the appropriate class to control them, specifically to allow the built in libraries to aid in scaling to give us a better response.

My thought is that teams would rather see results as though it was on their competition robot. However, it could be a great learning opportunity to run it both ways - then we could view concrete data on what the built in libraries actually do for us, and show the students the actual reason for doing things the way we do them.

Re: New Talon Speed Controller
 

I would agree, if there was a Talon or Victor 888 class.

Re: New Talon Speed Controller
 

Someone mentioned apples-to-apples in an earlier post.

An argument could be made that for purposes of comparing the various motor controllers to each other, you want to run them without intervening third-party software.

Re: New Talon Speed Controller
 

Thanks for the suggestions guys. We'll go back and retest the linearity under a constant-load scenario. We'll trying using the PWM as well, to see if anything is significantly different.

Also, it appears we've had an offer to start testing the Victor 888's. I'm fairly excited to get side-by-side comparisons for both new products. More variety is always a good thing.

Re: New Talon Speed Controller
 

Tom,

The beta test URL link in your sig appears to be broken. Or maybe it's just my DNS acting up again?

[EDIT] it works now, but the LabVIEW tutorial link doesn't [/EDIT]

Re: New Talon Speed Controller
 

Nope, it was my link. We just finished converting the whole site over to using Server-Side-Includes, and I didn't update the page extension to .shtml.

All fixed. And All Fixed again. Silly website revisions.

On another note, we're horribly behind right now. Our Labview 2012/13 installtion backfired on us. We were running administrator accounts, but we didn't right click the setup file and 'run as administrator'. There appears to be a world of difference when it comes to Labview between those two instances, so we're redoing 5 hours of Labview Installations.

Bleah.

Re: New Talon Speed Controller
 

That's so the rest of us don't have to.
Thanks for the effort and the warning:)

Re: New Talon Speed Controller
 

From my experience, this isn't just a Labview problem... this is a Windows 7 problem (I assume that's what you're using?). They've started switching us over at work, and a lot of guys I work with have had all sorts of trouble getting software to work correctly due to permission issues.

Still, it's good to find it now, so it can be called out in the instructions in January!