Quote:
Originally Posted by Greg McKaskle
Full disclosure -- also not an EE, that was only my minor. Also not a HW designer much less a power supply guru.
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Greg McKaskle
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Greg,
As to the fact that the actual RoboRIO blackout voltage was show to be 3.5V in one case, while I want to say good things about this, I just can't. The Spec you link to says 4.5V, I suppose that is what it was designed to be. One particular example showing a lower actual drop out voltage doesn't change that. Specs are about what happens to the worst built RoboRIO on its worst day. Am I happy that one particular data point is suggestive that there is design margin in that 4.5V? Sure. Do I wish that we were talking about a designed blackout voltage of 3.3V (or lower -- recall that as an ME my opening ask was for the RoboRIO and other key equipment stay alive down to 1V and was only talked off the ledge by my EE friends) and were talking about actual blackout voltages in the sub 3V range? Yes, yes I do.
BUT the RoboRIO reboot voltage is only one piece of the puzzle. The control system is a SYSTEM. Its nice to have a RoboRIO not rebooting but that is not enough. I need to have radio communications alive and well. I need to have my incremental encoders not lose their positions. I need to have my MEMS IMU keep its position for a the whole match (I'm looking at you navX). I need to have my onboard Beaglebone coprocessor not reboot during a match. I need to have sensors doing their thing. ...
It was FIRST's task to think on a system level and provide a system that just works.
As to the other things that FIRST/NI did right, I am not disputing this. There are a ton of things that FIRST/NI did really well. Protection against reversed and misrouted power/ground IS important and, as far as I know, the RoboRIO does a good job of this. Nice job on that front.
But that doesn't free the FIRST from the responsibility to manage power effectively. On this front, FIRST has a lot to answer for.
And now I will finish with the question I am promised to ask until it gets answered: How much would it have cost if FROM THE START OF A CLEAN SHEET DESIGN to have the RoboRIO, the Radio, 6V*, 5V & 3.3V rails all stay alive down to a Battery voltage of 3.3V?
I have a pretty good idea what the answer is but I would like to hear those who made the decision not to provide give their estimates.
Dr. Joe J.