[DFTF] Jags v. Vics...

[JamesCH95]

Originally Posted by slijin

This is only true during build season; the Jaguar discount is implemented, I believe, immediately following kick-off. To my knowledge, there has been no discount on Victors since 2010.

Ah, I see. I haven't purchased Victors since 2005...

That's a big price advantage to the Jags during build season then.

[AdamHeard]

We prefer the smaller weight and footprint of the Victors, although I understand that isn't a concern to many.

We've used Jags in various applications, but what always worries me is the 100-amp fault mode. We've triggered this when we drove defensive bots at home with jags in drive over and over.

Can the 100 Amp reset be removed if you use CAN?

I'll just never feel comfortable with them in drive powering a motor that will draw 133 Amps routinely.

[flameout]

Originally Posted by AdamHeard

Can the 100 Amp reset be removed if you use CAN?

Someone please correct me if I'm wrong, but I don't think so. However, you can reduce the time it shuts off after a fault is detected -- I think the minimum is half a second.

I'm not sure if this change is persistent -- maybe you don't need to use CAN on the robot, but rather connect as a one-off configuration step (then you can use PWM on the robot). Does anybody know if it's persistent?

[AdamHeard]

Originally Posted by flameout

Someone please correct me if I'm wrong, but I don't think so. However, you can reduce the time it shuts off after a fault is detected -- I think the minimum is half a second.

I'm not sure if this change is persistent -- maybe you don't need to use CAN on the robot, but rather connect as a one-off configuration step (then you can use PWM on the robot). Does anybody know if it's persistent?

That is an inadequate solution. I don't really understand the point of this feature, one would assume the designers of the Jaguar are aware of what motors we use?

[slijin]

Originally Posted by AdamHeard

That is an inadequate solution. I don't really understand the point of this feature, one would assume the designers of the Jaguar are aware of what motors we use?

To be fair, bringing the Jaguars to voltage fault, from personal experience, is very difficult. Last season, we did mecanum for the first time; believing that the potential for better control Jaguars offered was worth the departure from Victors, we set up a test drive base with Jaguars on a serial-to-CAN interface.

We ran into a number of issues with Jaguars; one in particular led us to do a number of stress tests to see how easily voltage faults were induced. Although the testing was relatively casual and we recorded no quantitative data, the only way we could ever induce voltage faults was by rapidly shifting from full forwards to full backwards multiple times within a few seconds.

To elaborate on other problems we had, I have to say that the issues began the moment we took them out of the box; I believe 3 out of an initial order of 9 were defects (configuration could not be accessed, did not respond to signal control, etc). More died after we put them onto an actual drive base; the most notable example was one that released magical blue flame in the middle of a driving tryout.

Other issues we ran into include CAN issues that could not be properly debugged because of issues possibly related to the proprietary code (as we could not effectively isolate said issues).

One point that I'd like to raise, non-performance related, is the encoder I/O interface on the Jaguars. One of their selling points is that they can be configured to run their own individual PID loops with encoder input, but that feature is somewhat tedious to utililze. The encoder input is a 5-pin PWM setup, whereas the USDigital optical encoders have a 4-pin output (Jaguars can take an index signal that these encoders don't). Most teams would have to cut up the KoP 3-pin and 2-pin PWMs and solder them to the encoder wires, which I personally find to be a tedious implementation. The alternative, however, requires teams to own the tools and materials necessary to produce their own 5-pin PWMs.

[Jared Russell]

Originally Posted by slijin

To be fair, bringing the Jaguars to voltage fault, from personal experience, is very difficult...the only way we could ever induce voltage faults was by rapidly shifting from full forwards to full backwards multiple times within a few seconds.

With a full traction wheel arrangement, it is much easier to induce these faults.

[apalrd]

We were able to repetitively fault out the Jaguars on our Lunacy shooter. Part of the spin-up process backed up the shooter wheel and feed conveyor (to get any moon rocks out of it), stopped the feed conveyor, spun up the drum, then fed the conveyor forward. This reverse/forward slam of a 6" diameter 24" long drum geared like 5:1 off a CIM was enough to fault the Jaguars on a battery that wasn't fully charged (e.g. 5 minutes into a demo, it would fail). If we had significant load on the drivetrain (any non-lunacy wheel), this time would have been very very short.

We haven't used Jaguars since the grey ones. We blew up quite a few that year, and combined with the overactive faults, were turned away.

That said, I have heard that the new black ones don't blow up as much as the grey ones.

[Joe Johnson]

Best Price on a Jaguar/Victor as of this minute is...

Digikey has them for $109. AndyMark has them for $119, but with a $20 discount for FIRST teams.

Is there a better place price to be had?

As to Victors, the 884 is $90 from Vex.

Again, is there any other source or discounts that I am not aware of?

Joe J.

[Aren Siekmeier]

During the season you can get a $25ish FRC discount on the Jags straight off Digikey, making them $84 (is the price I remember). Don't know of anything else for the Victor.