25-11-2006, 21:10
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FIRST's Spare, Queuer & Tech guy =)
AKA: Mike M. / Mouse =)
no team (FRC Volunteer)
Team Role: Alumni
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Join Date: Jun 2002
Rookie Year: 2001
Location: Staten Island, NYC
Posts: 1,504
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Re: 12Vdc 5mm LED Bulbs
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Originally Posted by Al Skierkiewicz
Mike,
All LEDs are about 2 volts forward voltage drop. You need to put a resistor in series with the LED to limit the current for the power supply you are using. There are some manufacturers that make filament lamp replacements from LED/resistor combinations for different voltages. If your plan is to replace filament style bulbs in your truck, it is also necessary to provide for reverse polarity using some diodes in addition to the resistor. The unfortunate problem with LED replacements for filaments is the directivity of the LED vs. lamp. If the application uses a lens or reflector, you may be unhappy with the results of an LED. If you are replacing LED's then there may be other problems that caused them to burn out in the first place.
In general, a single LED will require about 500 ohms in series to drop the voltage from 12 volts@20ma. 470 or 560 ohm resistors are the standard values close to 500. If you purchase a particular high brightness LED, follow the specifications for that device.
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Theres already a Resistor on the PCB from the old LED. =) The LED will be replacing one that is mounted to a 2000 Chevy Blazer Rear Wiper Motor / Rear Window Open Illuminated switch.
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Past FIRST Robotics Events that I proudly volunteered at: FLL: NY State Competition '03
FRC: NYC Remote Kickoff '04 & NYC Regionals '04-'15 ,'10-'13 & NJ Regionals '06-'10, Finger Lakes Regional '09 & SBPLI Regional '08-'15 and the World Championship in '05 (Galileo Field) '07 (Newton Field) '09 (Practice Fields Attendant / FTA(A)), CeBIT Convention in '04 & NextFEST in '06 both held @ the Javitts Center, Monty Madness '07-'10, Panda-monium '08, B.Eruption '08 & '09, Ramp Riot '08, PARC '09 & '10, BR^2 '09 & Wol. Inv. '09 -'15
2015 FIRST Robotics Off Season Events that I hope to volunteer at: Where is Wolcott Invitational 2015 FIRST Robotics Events that I will be volunteering at: SBPLI Reg. & Championships Volunteer Resume: Alt & Lead Team Queuer, Field Repair/Reset, Field Setup/Breakdown, Spare Parts Attendant, Field Power Controller/Score Keeper, Co-Emcee & Official Scorer, Control System Advisor, FIRST Tech Advisor Assistant & recently Practice Field Attendant.
Last edited by mtaman02 : 25-11-2006 at 21:13.
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