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Unread 08-05-2011, 17:13
qnetjoe qnetjoe is offline
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Re: Victors verses Jaguars?

Please let me chime on a few things here:
  • Jag Over Current Protection
    • Gearing - A good number of these issues really center around the lack of proper gearing. There is no subsuite for good mechanical design. For example, one of the teams at a regional I supported was trying to direct drive a 6" wheel with the CIMple gear box. This is about half of the proper gear ratio.
    • Stupidity - I don't know for sure, but I suspect that the reason that it was implemented had more to do with the rash of team that did not fuse their victors during the post 2008 off season. I personally saw at least 4 or 5 teams that wired victors directly to the rockwell PD block without any fusing.
  • Reliabilty - I have personally fried at least 10 or more victors and jags. In almost every case the problem was environmental and not a design flaw of either. Metal shaving and debris are not friends with any motor controller. One of the big problems with the Gray Jags is that the screws were not met to be taken out thus creating metal shavings. It would not surprise me if a third version of the Jag is released that it will be conformally coated.
  • CAN - CAN is still a work in progress and will be for the near future. CAN provides a gateway into the power of the Jag. The Jag can do 40+ MIPS (million instructions per second). Moving your control out to the Jags can have a major advantage if you are will to put in the time to get it to peform consistently and reliaibly.
  • Firmware Update? - Have you updated the firmware on your Jags? I know they changed some of these settings in one of the firmware updates. I updated the firmware of my gray jags to V92 vs the original firmware and the behavior is night and day.

The biggest piece of feedback that I can provide is that if something fails find out why. This is what engineering is about. Too many people blame the jags since they are just a symptom and don't find the root cause. The whole window motor is a great example. The Jag provides a more linear output (most of us could argue that this is better) and this creates an issue with the locking pin. The problem is not with the JAG but with the locking pin on the window motor (root cause); Yet people blame the Jag (symptom). You could replace the Jag with an industrial drive and have the same problem.

One of challenges of designing things for FIRST is that it can be used in so many ways; commonly in ways you never expect.
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