Since progressing with my mod I no longer need both (power and activity) LEDs that are on my internal card reader. I still want the activity light however but I'd like to swap the LEDs over because I want a green activity light and you've guessed it, its currently red! My question is would there be any 'current' difference between the 2 LEDs? I'd also like to just leave the other (power) LED cut off since I don't need it. Would this be ok or would I need to 'close the circuit?' I know I could get a volt meter but I thought someone might know? Any advice appreciated. Gizmo1990
It is perfectly alright to swap LEDs. The forward current should be about the same for every color LED unless it is one of those high mcd ones. For the forward voltage, since a red LED's forward voltage is slightly lower than a green's there should not be a problem. If you want to be cautious, insert a low resistor in series with the new red LED - 1-10 ohms should do the trick. Otherwise just leave as is and swap LEDs. You do not have to "close" the circuit in this type of scenerio as in grounding or bringing to anode. You can just encircle both wires in electrical tape and that will be enough.
does the above advice include most blue LEDs? I'd like to swap my CDROM drives' LEDs (green) for blue ones, but i've heard they can often have different properties to the more standard ones like green and red. If so will the 1-10ohm resistor be adequate for normal (not super-bright etc) blue LEDs? (spot the electronics n00b!)
Thanks Xiachunyi. Kingskin: I think blue LEDs (even normal ones) do indeed require a higher voltage. However, wait for someone else more qualified to post as I'm not 'that' sure!
Blue LEDs usually have a higher forward voltage and about the same current requirements, even if the current requirement is higher - it will just be dimmer. A direct swap can be used in place of the green LED on the CD-ROM drive. If the blue LED does not light up, the voltage being fed to the blue LED is not enough to correctly forward bias it. You must then trace the little trace from the LED to its current limiting resistor and replace it with a lower value one. The resistence can be calculated utilizing Bit-Tech's LED calculator. Generally forward voltage ratings go in the order of (highest to lowest): Blue, Green, Red - generally speaking but it is better to check the stipulations. To go from a higher voltage to a lower, you will add resistence and from lower to higher, you will subtract resistence simply speaking.
I've run accross a query during my LED swapping!? I've noticed that the 2 LEDs I want to swap over appear to be flipped? That is, I was expecting to simply move one over using the same orientation, however looking at the LEDs their diodes (?) appear flipped. Heres a photo to better ilustrate what I mean! My question is, does this mean I should 'flip' the green LED over to match the red LEDs orientation and vica versa?
that flat bigger part inside the LED is the negative end, (cathode)...so all you have to do it make sure you hook up yur new LED the same way. the way it is like that is because of how the circuitry was designed,
...so because the negative cathode on the red LED is on the left, I should flip the green one over (so its negative cathode is one the left as well) when I swap it with the red LED?
yes no matter what LED you hook up, the positive will have to connect to the positive (anode)...and the negative will have to connect to the negative (cathode). so no matter what led you put in...wire them up the same way they look now when you put the green one where the red one is at...make sure the negative side is on the left...and vice versa i just realized i messed up in my first post...i wasnt fully understanding what you said...so this is answering yur question underneath yur picture...sry bout that
Not always... I've had red LEDs where it was reversed. Quite annoying actually... I flipped them over so they would all be oritented the same only to find out I had them right to begin and then they were like oddballs...
