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Unread 25-01-2012, 08:09
Unsung FIRST Hero
Al Skierkiewicz Al Skierkiewicz is offline
Broadcast Eng/Chief Robot Inspector
AKA: Big Al WFFA 2005
FRC #0111 (WildStang)
Team Role: Engineer
 
Join Date: Jun 2001
Rookie Year: 1996
Location: Wheeling, IL
Posts: 10,808
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Re: Banebots RS-775 Case Short

Everyone,
I think it is important to state the effect of shorted motors on FRC robots. In the event of a shorted winding to the armature, there is likely to be no significant degradation of performance in our applications. Only quality control style testing would indicate a drop off in speed or power and then only when measured using the type of instruments used in this testing. Where problems will arise on an FRC robot is when wiring errors occur on the robot such that an additional electrical path is established through both the shorted motor and the other fault. If this second path is established through the Crio chassis which is electrically tied to the negative terminal of the battery, the Crio +24 volt power supply will be compromised and that will result in Crio reboot. If the second path should be through a second motor, a variety of faults could occur. While none have been documented, these could be anything from tripped breakers to power supply fluctuations to electrical component failures. We all know that a simple test for frame continuity may not show a defect until the motor is rotated to where the short is actually connected to a brush within the motor. A single shorted motor on a properly constructed FRC robot should not (in and of itself) cause any additional failures. In the event of a short as witnessed in 2011, the frame of the robot would be alternately switched to the negative lead of the battery or the positive lead of the battery dependent on the motor direction command of the controller. As inspectors we are very concerned about frame shorts of any kind for two significant reasons. One occurs when two faulty robots become engaged and there exists two paths through frame and other electrical wiring that may cause significant damage to electrical components or sparks. The second is our desire to insure every team plays every match and is able to be competitive at every event they attend.
When you are building your robot please keep in mind that the Crio must be electrically isolated from the frame and that all electrical wiring be insulated. When an inspector points to something during the inspection process, he/she is trying to help you. He/she wants you to perform at your best. Good Luck.
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Good Luck All. Learn something new, everyday!
Al
WB9UVJ
www.wildstang.org
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Storming the Tower since 1996.

Last edited by Al Skierkiewicz : 25-01-2012 at 08:12.