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Unread 25-03-2007, 13:55
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
 
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Rookie Year: 1996
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Re: Voltage difference in PWMs

So there is no confusion in interpreting all the answers...
The PWM outputs of the RC are powered by the backup battery (7.2 volts) and the power pin is used on any servo connected to one of these outputs. The signal line of the PWM output is generated by the RC processor and is conditioned (opto coupler, noise filter, etc.) at the input of the Victor or servo as designed. The Victor does not use the 7.2 volt pin. The power for the Victor is derived from the main battery and the output is switched main battery voltage. The output of the Victor varies pulse width not voltage and in so doing varies the average current in a motor to control the speed. If you were to look at the output with a scope you would see a sqare wave of varying pulse width but the peak voltage would be the same as the main battery less the voltage drops due to wire losses and the series resistance of the FETs in the Victor. The output of the Victor changes polarity (M+ becomes negative and M- becomes positive) when the signal calls for the output to be reversed.
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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.