Did you observe this behavior in both the Tan and Black Jags, or the Tan Jag only?
I ask because Gdeaver reported in an earlier post that the Black Jags use locked anti-phase switching.
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The black Jag behaves straight-forward that way with or without a load.
A long time at 0v/short time at max volts, progressively shorter time spent at 0v, until it’s full time at max volts.
The top end dips only in response to dropping battery voltage as the load draws more power.
So this whole thread just the result of measurement error?
Put simply, it would be physically impossible for a Jaguar (or a Victor) to have an actual 2V drop while driving a motor and not be on fire: It is WAY too much heat to dissipate.
80 watts IS a lot, isn’t it?
I wonder why infineon claims each power transistor can dissipate 100 Watts?
Anyways, I would appreciate getting back to the original topic. I recently obtained a Jaguar that has this problem. (I’m not sure what was done to it.)
The only damage I see is around the traces on ONE of the MOSFETs. However, I get no voltage both in Forward and Reverse.
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I think the discussion was fruitful, and produced a useful bit of knowledge:
An inexpensive multimeter (affordable by any team), set to read DC volts, should read the same voltage at the power inputs and the motor outputs of a Jaguar (either tan or black, or a Victor) when the Jag (or Vic) is being commanded full throttle and has a motor connected.
This knowledge is useful for helping teams to diagnose/troubleshoot Jag/Vic problems. Thanks Mark for the effort you put into running the tests.
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That spec only accounts for the junction to case thermal resistance and assumes a perfect heatsink with infinite mass at 25C. Power MOSFET specs are actually pretty funny when you look into the assumptions made.
I’m still confused as to what is going on. How is this different than the ESD issue?
How is the “no power out” different from the ESD issue?
Did I miss something?
In order for ESD to be a problem, wouldn’t the case have to be opened up. You’re saying the case was opened up while the Jaguar was still functional? Why would someone do that?
Or is it something else entirely?
Marshal,
The ESD issue didn’t need the case to be open. During the 2009 game, the regolith especially in ice arenas produced some rather extensive static lightning strikes for robots and field. Some of these events punched through the case or traveled along the wiring and took out some components. The early Jags also had an issue with the FET gate drivers that would self destruct and usually caused a single direction failure.
Does that mean I can return it for replacement?
I would recommend that you read the Jaguar Failure Analysis (FA) report, and then at least attempt an RMA. Both are linked from the luminary micro jaguar FRC site. Your Jaguar is probably out of warranty, but it doesn’t hurt to try, and at least lets TI know the extent of the problems.