Quote:
Originally Posted by Al Skierkiewicz
The devices you think are 317's are in fact IRL3103 Power MOSFETs in the Victor. As Eric pointed out the large cap on both the Victor and the Jag are to smooth power supply. 317s can't handle brake mode, make a minimum of 1.25 volts output when the control input is grounded, can't control 40 amps each and require a large diode for reverse polarity protection.
As to the resolution, most teams don't use the ~120 bits (accounting for the deadband and only one direction) as it is and most don't even calibrate the controllers.
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Ah, that makes a lot more sense. I was wondering how they would get by the 1.25 reference voltage of a LM317. I guess they COULD use LT3080s to get around that, but like I mentioned before, I haven't taken a Victor apart (mostly because they're not mine, and our team doesn't have the kind of resources to waste on me accidentally breaking a Victor).
The reason I mentioned that it would be nicer to have more resolution is well...put it this way. This year, the majority of teams (including 3138), had shooter wheels with a speed controller. If your max speed (that is full voltage to the motors/128 counts) is 4000 RPM, which is easily attainable, the finest you can change your motor speed by is ~30 RPM, which can be a heck of a difference. I'm sure there's got to be a way to use it as an unsigned value (that is 0-12V rather than -12-12V) to get 256 counts of resolution, but that would still only give you a 15 RPM resolution. While many teams figured out it didn't make a huge difference, it would be nice from a controls perspective to be able to control it down to a single RPM (which would be attainable with a 12-bit PWM signal)