Swapping Out LEDs to Change Color

jedihobbitjedihobbit Central Virginia, USA New
edited July 2010 in Hardware
As part of the “as yet to be named” build I plan on replacing the blue LEDs that are part of the Zalman ZM850-HP that is in its future. Currently they are the usual “blue” and wish to replace with green.

While I have no issues with de-soldering and soldering, component selection will be. In my limited knowledge I believe I’ve read somewhere that just because it is an LED doesn’t mean they are all the same. Soooo was wondering if there may need to be a resistor or something that will need to be in the circuit? :confused2

While on the subject of soldering, as I don’t do that much and no longer have a soldering tool…….which would be better the traditional “iron” or the racing looking “gun”?

Comments

  • drasnordrasnor Starship Operator Hawthorne, CA Icrontian
    edited July 2010
    You want to try to match the physical size of the LED you're trying to replace (typically either 3mm or 5mm) which will require you to pull the original LED fan. Once that's done, buy an LED that will fit.

    You will almost certainly need a current-limiting resistor but to size it you need to know the LED supply voltage and the supply voltage from the power supply. If it's an LED fan then the latter is probably 12V. The equation Rl = (Vs - Vl)/Il will give you the value of the LED current limiting resistor Rl for supply voltage Vs, LED rated voltage Vl, and LED rated current Il. That information will be in the LED datasheet.

    I prefer a soldering pencil for this sort of work. I have a really nice Metcal soldering station but the Weller 25W or 30W pencil is perfectly adequate. The gun is for soldering big hunks of metal like copper pipe or power conductor and will probably melt/set fire to your PSU's guts. You'll want to get some fine-gauge 63/37 rosin-core lead solder; 60/40 lead is okay but the green lead-free stuff sucks. For splicing wire you'll get good results by tinning each conductor with a small amount of solder and then sweating the conductors together.

    To be totally honest though, you'd be better off just replacing the LED fan as an assembly. Buy one that's the same size as the one inside your power supply with a nice bearing and the LED you want and solder that in place of the old one.
  • RichDRichD Essex, UK
    edited July 2010
    Please correct me if im wrong as my electronics knowledge is pretty patchy but surely, if you are swapping an LED the old LED will already have the resistor in place? Wont it just be a case of swapping the LED for another one that is the same physical size as the other?
  • SnarkasmSnarkasm Madison, WI Icrontian
    edited July 2010
    Depends what you're swapping it from and to. Red LEDs require less power than blue or green, etc; white has different power requirements than amber; so on and so forth.
  • RichDRichD Essex, UK
    edited July 2010
    That I did not know! Do you happen to know the difference in power between Red and Blue. I converted a set of Technics 1210 Record Decks to Blue LEDs and just swapped the LEDs. Im wondering if I need to add some extra resistance?

    They seem to work but I am now worried about their lifespan?
  • drasnordrasnor Starship Operator Hawthorne, CA Icrontian
    edited July 2010
    Technically, red LEDs require lower voltage than blue LEDs to reach their design current consumption. If the system was designed for a red LED then it ought to be able to drive a blue LED without modification though the blue LED will be emitting less than its specified brightness. This increases the life of the LED and if it's bright enough for you then it should be fine.

    As a rule of thumb, you can go from longer wavelength LEDs to shorter wavelength LEDs without changing the resistor though you'll lose some intensity as you'll be driving the new LED at a lower voltage. Going the other way you need to modify the resistor since the short-wavelength LEDs require higher operating voltage than what the long-wavelength LEDs are rated for.
  • RichDRichD Essex, UK
    edited July 2010
    Cool. Thanks for the advice and sorry about hijacking the thread!!!
  • jedihobbitjedihobbit Central Virginia, USA New
    edited July 2010
    RichD wrote:
    Cool. Thanks for the advice and sorry about hijacking the thread!!!

    No hijack that I noticed! :confused::eek::wink: :bigggrin:

    Hope to have some parts to play with by next week. I'm sure the assembly I'll be attacking has the resistors hardwired. Will just have to see if an extra will need to be inserted or if a total replacement will be required. :crazy:
  • tmh88tmh88 Pittsburgh / Athens, OH
    edited July 2010
    Just use a multimeter to get a reading off of the circuit and then find LED's according to that. Any decent manufacturer will include specs of their LED's.
  • trolltroll Windsor, Nova Scotia Icrontian
    edited July 2010
    Good little calc for current limiting resistor size...

    http://ledcalculator.net/
  • jedihobbitjedihobbit Central Virginia, USA New
    edited July 2010
    Thanks for the input guys......still have to get back to this!
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