[dsirovica]

Al: Thank You for bring us back to earth!

It is by no means necessary to be able to follow this debate in order to be a great FIRST participant.

One of the genius ideas behind FIRST is that it enables kids of different backgrounds and skills to actively participate by leveling the playing field. The design of the KOP, the game rules, strategies, community effort, etc. The body of knowledge behind the scenes and the way it is organized to serve a noble cause is just phenomenal.

As a new mentor, and one of the little cogs in the FIRST ecosystem, I was dismayed when one morning after another 1AM night of frantic redesign a few days before bag-day, the robot showed up with all its Jags replaced by Vics! The reasoning was – they kept cutting out, we always have problems with them, we've always switched back to Vics and we carry a bag of replacement Vics as they die!

Well needless to say, in the professional world, this is not a satisfactory assessment of the situation and resulting decision...

BTW, on a more humorous note, that same night when the kids where left home alone :-) our robot almost went for a midnight skinny dip – one wheel was over the edge of the pool! Maybe it was a Jag that prevented that fiasco!

I see the pursuit of this thread as a way to close one of a gazillion of open issues that many struggle with and forever debate on these fora. I believe that a little extra effort to push for a definitive understanding and resulting recommendation is going to save this community a huge effort. We must though ensure that the mechanism exists to capture, save, and make this knowledge readily available when next time someone asks Jag vs. Vic? Can you just imagine what the total effort spent on this is ? Our team has spent many person-days on this just this season. It has a huge spill-over effect too. Our mechanical design called for a JAG-based PID shooter control, so all that work is down the drain too!

Back to the topic for a moment:
Thanks Mark for the latest Vic PN 2N03L13
It is very similar to the other one I used in the math FDB6035AL
The parameter of interest is RDS the New PN is
10.3mOhms(25C), 15.5mOhms(150C) so just a little better – not too significant.

BTW: in my posted equation for the MOSFET Power dissipation I forgot to show the Pswitching contribution, so the formula should be
P= I^2*R + Pswitching which is 0.5W for our Jags and 0W for Vics

The numbers presented are still valid.


Al is also right – as others have said – we are investigating an area of operation that is near, and beyond the “red-zone”. Proper design would call for staying well clear of the edge of the normal operating zone (kids take note!). Jag designers know that, so they designed the cut-outs to ensure the system stays clear of that zone. We all know that once a system is deployed it will be pushed -accidentally, or on purpose, to its extreme. So the Jags just cut out, while the Vics burn!

It is like the 0-11 setting in the Spinal Tap amplifier :-) users want, and will always push to go to 11!
So I do think the Jag should allow for an “11” option and a disclaimer User Beware :-)

Seriously, IMHO, the Jag can relax its protection a bit and still be quite safe. Especcially I think there could be two modes (1) for regular long steady-state operation, and (2) for short bursty operation like a FIRST competition. Yes yes I can hear you say users of (1) will use the (2) setting to solve a mechanical design problem... c'est la vie!