coozer
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| posted on 4/3/12 at 03:33 PM |
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Wiring LEDS?
Looking through my Omex manual it says a shift light with a LED in it needs a resistor...
Is this true and if I wire up say 8 of them to a single feed waht do I need?
Maybe a school boy error instead of using normal bulbs?
Steve
1972 V8 Jago
1980 Z750
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loggyboy
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| posted on 4/3/12 at 03:40 PM |
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Depends on the specs of the LEDs.
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BenB
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| posted on 4/3/12 at 04:30 PM |
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Yes you need to find the voltage they are rated to run at. You will need eight resistors (one for each LED) unless they are all going to be on at the
same time in which case you can put the LEDs in parallel and run a single resistor or even run the 8 LEDs in series (they'll get 14v/8 each)
which is what about 1.8v?
But anyway as said, depends on the specs of the LED.
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MikeRJ
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| posted on 4/3/12 at 07:23 PM |
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quote:
Originally posted by BenB
Yes you need to find the voltage they are rated to run at. You will need eight resistors (one for each LED) unless they are all going to be on at the
same time in which case you can put the LEDs in parallel and run a single resistor or even run the 8 LEDs in series (they'll get 14v/8 each)
which is what about 1.8v?
Running LED's in parallel is not a good idea. They are not like light bulbs that will equally share the current if wired like this because
LED's have a natural spread of forward voltages, and the LED with the lowest forward voltage will hog the majority of the current. These means
you get a variation in brightness across the LEDs and also you may exceed the ratings of one or more LED's. The Chinese do this in their cheap
LED torches because it saves a few pennies and they don't care if it looks crap or lasts 5 minutes. For the cost of the resistors it's
well worth doing it properly.
However, with a 12v supply you can run more than 1 LED in series to reduce the number of resistors and the amount of wasted power. For white LEDs
with a Vf of about 3.4v you can run up to 3 LED's, though if using a resistor to limit current I would stick to 2 LED's to reduce the
change in current over the normal range of battery voltages.
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