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Unread 13-02-2012, 10:01
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: 10,798
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Re: Running PD Board from an outlet

Everyone,
Motors can produce significant currents at start up. My 35 amp linear supply will go into over current protect on an FP motor. Not only does the supply need to be able to handle large currents, it must also be able to handle startup current and be low impedance. You might find one cheap but in general, the cost for a line operated supply is likely too costly for most teams. Most inexpensive car chargers simply put raw rectified current into a battery. This is pulsed at power line frequency and could be either halfwave or fullwave rectified power. Even a battery connected across the charger will not take care of all the transients. Bench supplies can be had to run the PD and Crio along with controllers and relays as long as there is no load on these devices. Any CB power supply available at Radio Shack will likely be able to handle the current. I have a 5 amp supply at home that we have used from time to time.
As to computer power supplies and most switchmode, line operated supplies...
These devices generally rectify the incoming line voltage giving them a ~160 volt primary power supply. It is the capacitors in this part of the supply that carry the high voltage warning. The caps across the low voltage supplies are generally small in comparison and only carry the rated voltage (+/-12, +/-5).
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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.