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Unread 07-02-2011, 07:59
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
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Re: 9 motors too much?

Quote:
Originally Posted by Ian Curtis View Post
We tripped one once in 2006...
then running it into the drivers station over and over (which kept the CIMs fairly close to stall)
Ian,
Is it possible you may have tripped due to mechanical stress on the breaker?

For others, the internal resistance of the battery is 11 milliohms. At 500 amps, there will be only 5.5 volts dropped across this resistance which is still enough voltage to power the PD power supplies and keep the Crio and radio up (and therefore your robot). Using smaller snap action breakers does not limit the current to the motors. A CIM will still stall at 133 amps regardless of breaker size. If you use a smaller breaker and then use smaller gauge wire, there can be significant resistance in the wire to limit the current through a motor. The down side to this option is reduced motor performance.
Caveat:breakers that are tripping will heat up. If you hear a buzzing noise from your robot, do not touch the breakers when the robot comes off the field. You will be left with an impression of the breaker size on your finger tip for several months.
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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.