Does it make any difference where in the circuit the resistor is placed (before or after the LED)??
ie, +12V - LED - Resistor - earth
or +12V - resistor - LED - earth
Simple one but cant find a definate answer
Cheers
Definitw answer - no
if there was a power surge 
the resister would blow and save the diode
Sorted!! Thanks
No difference.
quote:
Originally posted by Mr Whippy
if there was a power surge
That will be the fuse should
there be a power surge. When is does go, often the plastic cover gets blown off too I have to say I think the resistor would not save the LED, it will limit the current that will flow at 12V to a level that's safe for the LED but if you suddenly had a voltage surge from an electrical fault it would allow a proportionally higher current, potentially enough to blow the LED. You'd need to know the safe amps limit of the led and fuse it to that level, i'm not sure if there's any point though...?
I do of course reserve the right to be completely and utterly wrong.
Well i have wired in the LEDs the other way around to the "norm" now as I had already done the circuit board with the resistors on "the
other way" and wasnt about to change it unless i had to. If an LED does blow then a new one is 19p and a few mins soldering so not enough to
worry about.
Martin who i am building the car for is an electrician so i think he'll be fine.
Just found this:
http://www.kpsec.freeuk.com/components/led.htm
Hope it helps.
Martin.
quote:
Originally posted by martinq357
Just found this:
http://www.kpsec.freeuk.com/components/led.htm
Hope it helps.
Martin.
Or you could just get 12v LEDs from the likes of Maplin. 30-40 pence & no resistor to worry about!
Know what you mean Mr Whippy. My old car got LED's fitted (by me) when i fitted a carbon dash and the main beam warning was blinding!! I changed the resistor so many times to turn the brightness down but still dazzled me.
I have found this LED ARRAY WIZARD useful in the past.
Neil
quote:
Originally posted by trikerneil
I have found this LED ARRAY WIZARD useful in the past.
Neil
LED array wizard is brilliant !!
quote:
Originally posted by Mr Whippy
Hope it helps.
good find. Anyone know why blue LEDs are so dazzling even at a distance with a big halo around them? I suspect it is the short wavelength light refracting inside the moisture on the surface of the eye.