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Unread 09-05-2005, 07:39
Unsung FIRST Hero
Al Skierkiewicz Al Skierkiewicz is offline
Broadcast Eng/Chief Robot Inspector
AKA: Big Al WFFA 2005
FRC #0111 (WildStang)
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Re: Victor Burnouts

Quote:
Originally Posted by Sparks333
Al,
I can't remember the team number, but I will see if anyone else does.

Sparks

PS: Are FETs sensitive to polarization? I think they are, but I don't want to make false assertions. IFI Robotics has a notice on the vics page that says:

Is it such a jump to say that using an output as an input would have much the same affect?
It is not the FETs that are damaged by hooking up the power incorrectly, the drive circuitry is not protected from reverse polarity. These FETs do have protection zener diodes in the construction (as pointed out above) so reversing the power to the FETs will cause the diodes to conduct with a 1.2 volt drop. When the Victor is off and the motors are turned, the diodes conduct and the only path is through the rest of the driving circuit and back through ground. Since they are in a bridge configuration, the direction of the motor doesn't matter. Theoretically, there is nothing to limit the voltage produced by the motor, but with two diode in series, there is a 2.4 volt drop before anything else comes into play. I agree that it is unlikely that damage will result from a backdriven motor in power off.
I agree that the brake will not be applied unless the controller is enabled now that I think about it. All PWM outputs are disabled unless the OI and RC are talking and enabled. The brake should only cut in during a PWM 127 +/- the deadband right?
__________________
Good Luck All. Learn something new, everyday!
Al
WB9UVJ
www.wildstang.org
________________________
Storming the Tower since 1996.
 


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