View Single Post
  #14   Spotlight this post!  
Unread 10-04-2009, 07:54
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: 10,766
Al Skierkiewicz has a reputation beyond reputeAl Skierkiewicz has a reputation beyond reputeAl Skierkiewicz has a reputation beyond reputeAl Skierkiewicz has a reputation beyond reputeAl Skierkiewicz has a reputation beyond reputeAl Skierkiewicz has a reputation beyond reputeAl Skierkiewicz has a reputation beyond reputeAl Skierkiewicz has a reputation beyond reputeAl Skierkiewicz has a reputation beyond reputeAl Skierkiewicz has a reputation beyond reputeAl Skierkiewicz has a reputation beyond repute
Re: Using the cRIO to control custom lights

Hal,
The RC network is not really needed but your LED string does need some series resistance to limit the current in the LEDs. Current to the base of the transistor is limited by the 10k pullup resistor in the DSC. To fudge the calculation I start with 2 volts per LED so on a 12 volt supply, that allow for 5 LEDs in series and a series resistor. Calculating 2 volts and 20 ma for the resistor gets you 100 ohms. In reality the LEDs are less than 2 volts but as the battery output drops, the LEDs will stay on.
__________________
Good Luck All. Learn something new, everyday!
Al
WB9UVJ
www.wildstang.org
________________________
Storming the Tower since 1996.
Reply With Quote