Re: REV Sparks or Vex Victor 888?
 

We have provided SPARK motor controllers to Richard and Ether to perform this testing series on them http://www.chiefdelphi.com/media/papers/2720

They would like to test the other new motor controllers also but need to get samples.

Re: REV Sparks or Vex Victor 888?
 

As Greg says above, Ether and I will be testing the SPARK for linearity in the same way that we tested the Talon, Jaguar, Victor 888, and Victor 884 a few years ago. REV has sent us SPARKs for testing and we plan to begin next week -- I have spent some time this week validating the test set-up.

I agree that it would be good to test newer controllers using the same methods. I will check to see what 3620 can provide. If anyone can help with samples of newer FRC-legal motor controllers we will be glad to include them in this round of linearity testing.

Re: REV Sparks or Vex Victor 888?
 

Richard,

Are you also referring to the Talon SRX and Victor SP when you are asking for "newer sped controllers"?

From my records, you have plenty of SPs and SRXs to do the testing but let me know if you need more.

Paul

Re: REV Sparks or Vex Victor 888?
 

Omar, I hope you or others in the FIRST community do not misunderstand. 2015 was by far the smoothest season I have experienced when running CAN. That is largely a result of the hard work and dedication of the folks at CTRE, and the best part is that I think we can expect it to continue improving!

I personally did not contact you during the season because I significantly scaled by my involvement during the 2015 season to finish my Master's thesis. The rest of the team is far less active on CD, so I am unsurprised that they would not take this initiative either. Furthermore, I had actually entirely forgotten about the strange behavior during that one practice match until prompted to comment on my experience with CAN. It never came back to bite us again, so it was a small blip on the radar compared to other problems we were working on throughout the season.

My mistake on the inaccuracy of the description of the mode changing issues. Looking back at my notes, the intended control strategy was to start the match by driving the relevant mechanism to a mechanical limit using set voltage, until it hit a current spike. When this occurred, we would switch to positional control mode with the mechanical limit sensed by the current spike as our 0 reference for use with our optical encoder feedback to know the absolute position. It was this mode change from set voltage to set position that took more time to figure out than anticipated (over a week). We figured it out eventually, but I would still contend that we would have more quickly been able to use current feedback from the PDP and a PWM motor controller with encoder feedback through the digital I/O, leaving us more time for practice. This was more an issue of us not having the existing know-how, but it should still be factored into a team decisions on what motor controllers are used in season.

I generally look to teams like 118, 254, 1114, 1678, etc. as rational decision makers. The fact that 2016 is the first year 254 comes out and says CAN warrants consideration for them is significant from this perspective for a few reasons:
1. Shows how far the implementation of CAN for FRC robots has progressed as a result of the hardware and other improvements (Talon SRX, etc.).
2. If a team with the man-power, expertise, and monetary resources of the Cheesy Poofs is just NOW in 2016 stating that the benefits of CAN may outweigh the costs for them, it should follow that a team with significantly less resources may be better off sticking to the simpler plug-and-play functionality of PWM.
3. Once more and more of these high profile, powerhouse teams start switching to CAN, we may start seeing teams capable of executing something more efficiently or elegantly as a result of using CAN. More resources will become available for teams to learn about how to use CAN. I do envision a future where CAN will be the sort of go to for motor controllers in FRC. The cost-benefit analysis for a vast majority of teams may someday favor CAN motor controllers. Performing this cost-benefit analysis for Team 5811 (rookie team) for this season simply reveals that it is not there yet for us.
(Already some great stuff from CTRE, but the more the merrier:
http://www.ctr-electronics.com/Talon%20SRX%20User's%20Guide.pdf
http://www.ctr-electronics.com/Talon...e%20Manual.pdf)

I am no longer mentoring Team 20, but I will send you an email to start the conversation and include others who were more intimately involved with programming the robot. My apologies it took this long to surface.

Re: REV Sparks or Vex Victor 888?
 

That's a pretty good excuse :)

Re: REV Sparks or Vex Victor 888?
 

I agree with what you are saying, but I would like to emphasize for all that each team should choose based on what they personally weigh for pros and cons. An important aspect of FRC IMHO is making trade off, if you follow what a team like the Poofs does because they are the poof then you are not truly learning.

Just a plug for the importance of making your own desicions rather than following others. ;)

Re: REV Sparks or Vex Victor 888?
 

To add to this. Victor 884s and 888s have no advantage over the other controllers. In fact, they have disadvantages that have been pointed out (difficult to wire, no passive cooling, exposed FETs.

The only reason I can see teams wanting to use them would be for the cost (as in teams have those stockpiles), and experience (I know they work. They've worked for us for 10 years, why change).

FIRST making them illegal would be a bad move, especially after the Recycle Rush game. Sure teams wouldn't just throw them away, but their usefulness will obviously suffer.

Re: REV Sparks or Vex Victor 888?
 

That graph was actually taken directly from the 2013 fighting pi beta tests on our Web page......... I guess I need to start watermarking the graphs.

http://www.fightingpi.org/Resources/...12_Day_9.shtml

Re: REV Sparks or Vex Victor 888?
 

Tom,
If you have any interest in testing the SPARK I will gladly send a few your way to run the same test.

Greg

Re: REV Sparks or Vex Victor 888?
 

Sure thing greg. You have a pm.

Re: REV Sparks or Vex Victor 888?
 

I'll second this. I'm speaking from the perspective of a team that, after getting tired of dealing with the headaches of CAN in 2012, switched to PWM, then most of our students and mentors experienced with CAN left. Wiring the new CAN system is a lot easier than wiring PWM (these things make it even easier, highly recommend them), but the configuration interface takes a little getting used to, especially for teams that have no experience with CAN. We had some trouble with the CAN configuration system being a little glitchy (although this was probably our inexperience) so I'd suggest learning how to use it before you have to do it on your competition robot. We had no issues using the built-in limit switch and encoder inputs. Overall, CAN was a very pleasant change for us, especially now that we have experience configuring it properly.

Re: REV Sparks or Vex Victor 888?
 

Just completed some basic Spark Linearity testing:

http://www.fightingpi.org/Resources/...ntroller.shtml

Re: REV Sparks or Vex Victor 888?
 

If i were in your position, i would use victor sp's. they are a new generation of victors and they don't make any sound, don't get warm, which means there is no need for a fan.they are also pre-wired out of the package, and I have shown great improvement with my electronics board.

Re: REV Sparks or Vex Victor 888?
 

They also cost a lot more. Sparks don't need a fan and don't get too warm either, according to the tests.

Re: REV Sparks or Vex Victor 888?
 

Sparks look pretty good to me also. So do the Victor SPs and Talon SRXs.

Ether and I have been testing several controllers, collecting data for a comparison of linearity (speed vs. PWM command) over a range of CIM motor shaft loads. I have some of his raw data now and will review that tonight, then post some graphs. I think the initial round of data will only compare Spark against Talon SR -- the older screw-terminal model.

As others have commented (see especially the Fighting Pi data that Tom Line linked), Sparks have a good design for transporting heat out of the power components. I have not made any laboratory thermal tests yet, but I think REV has some data. The Average Joes have run Sparks on a demo robot with no complaints -- the original controllers in that demo were Victor 888s and we've seen no significant difference.