system
April 27, 2005, 12:00am
#1
Originally Posted By: cfuoco This post was automatically imported from our archived forum.
I am installing 5 of these LEDS in series from a 12 volt power source. Can anyone tell me what size resistor I need?
http://www.theledlight.com/pdf/042004/YZ-R_3mm_red.pdf
system
April 27, 2005, 12:00am
#2
Originally Posted By: bking This post was automatically imported from our archived forum.
You need a resistor in series with those 5 leds rated at 2 to 5 ohms and one half watt.
–www.BAKingHomeInspections.com
system
April 27, 2005, 12:00am
#3
Originally Posted By: cfuoco This post was automatically imported from our archived forum.
Thank you Bruce
system
April 27, 2005, 12:00am
#4
Originally Posted By: Greg Fretwell This post was automatically imported from our archived forum.
Doesn’t sound like enough ohms to me.
Leds drop about 2 v and you end up with 2 at the end, across 2 ohms is 1 amp. That’s 2 watts. I would start with 50-100 and see if they are bright enough. A LED needs about 15ma to be usable.
system
April 27, 2005, 12:00am
#5
Originally Posted By: bsumpter This post was automatically imported from our archived forum.
Using OHM’s law, if you know the Voltage, divide it by the Amperage, and the result is the resistance needed to complete the circuit.
Ohms Law is a mathematical equation that shows the relationship between Voltage, Current and Resistance in an electrical circuit. It is stated as:
V = I x R
R = V / I
I = V / R
Where
V = Voltage
I = Current (I stands for INTENSITY)
R = Resistance
Hope this helps somewhat !
--
system
April 27, 2005, 12:00am
#6
Originally Posted By: bgriffin This post was automatically imported from our archived forum.
This will calculate for multiple LEDs in series.
Bud
system
April 27, 2005, 12:00am
#7
Originally Posted By: phinsperger This post was automatically imported from our archived forum.
Using Bud’s link I came up with 10 ohms 1/4W
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Hinsperger Inspection Services
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system
April 27, 2005, 12:00am
#8
Originally Posted By: bking This post was automatically imported from our archived forum.
The specs ref. in the question said 2.3v per LED and 50ma current
using the resistor calc. from Bud, it says 10 ohms 1/4 watt
its not that critical for LED's, depends on the brightness you want.
You can use 5 to 20 ohms and be ok, I would use a 1/2 watt instead of a 1/4 though for good measure.
--www.BAKingHomeInspections.com
