Help me change LED bulb please!

Discussion in 'General Electronics Chat' started by Borat, Nov 12, 2009.

  1. Borat

    Thread Starter New Member

    Nov 12, 2009
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    0
    Hey guys, I'm new to electronics, so I though I'd better ask pros

    I have external hard drive enclosure which lights up in blue, but I would like to change LED bulb so it lights up red. I have no idea which bulb I need, but I know its a 3 pin led. http://img9.imageshack.us/img9/9057/dsc00621ni.jpg
    Sousing from : http://img40.imageshack.us/img40/2880/dsc006302.jpg

    The LED is always blue (see through with no power ON), it constantly flashes, being a small flash even when HD is inactive and stronger, brighter flash, when HD is spinning, being used

    Could you please advise me how to change this Tri-colour LED to work in RED.

    I can get voltmeter to measure ΔV, λ etc, if you tell me how to operate it.


    PS. I am a TOTAL noob in electronics! Although I will be able to use a solder!
     
  2. Borat

    Thread Starter New Member

    Nov 12, 2009
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    Any one know?
     
  3. BMorse

    Senior Member

    Sep 26, 2009
    2,675
    234

    You do not have a Tri-Color LED, basically just 1 led with a built in blinking circuit (blinking circuit could be on the controller board itself, instead of being built into the LED), so if you just connect the red wire to +5 through a 330 ohm resistor), and connect the White wire with blue stripe to ground you should see it blink, if you connected the solid blue wire to ground, it will be on bright blue......

    They are using the blinking circuit just as a power indicator, the second function of the LED is tied to an active low output from the HDD activity LED pin, so it pulses brighter with HDD activity.......

    So if you want to change your LED to RED, just connect it to the RED and White/Blue stripe wire..... this should make it to where it will be constantly on, if you want it to blink when there is HDD activity, connect the LED's cathode to the blue wire....


    My .02
     
  4. Borat

    Thread Starter New Member

    Nov 12, 2009
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    Will these be suitable?
     
  5. parawizard

    Member

    Jul 23, 2009
    10
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    Looks like a 3mm. It won't be very detrimental to match specifications in that use but more size to fit into the enclosure.
     
  6. BMorse

    Senior Member

    Sep 26, 2009
    2,675
    234

    maybe if you have a multi meter with current reading capabilities, you can measure the current draw of the LED in the case, and find an exact match to replace it.... or you can just go with a higher current rated LED, but use a transistor to turn it one, since the Hard drive indicator is an active low output (Most people think the LED's V+ is switched, but the V+ is constant it is the V- that is controlled by the HDD activity indicator circuit) you will need a PNP transistor and a pullup resistor for the base.... If you are just going to use it as a Power indicator, just find a suitable resistor for whatever LED you purchase and connect it to a +5 source from the circuit....

    So are you just wanting a RED LED to indicate power and not blink to any activity?? If so any RED LED will work, better yet get a super bright diffused one so you can see it from any angle....

    My .02
     
  7. someonesdad

    Senior Member

    Jul 7, 2009
    1,585
    141
    Measure the operating voltage -- blue and red LEDs often have different forward voltages. You might have to put a resistor in series with the red LED if it would exceed around 20 mA current draw.
     
  8. Borat

    Thread Starter New Member

    Nov 12, 2009
    5
    0
    Hey, thanks for the answer Morse! for once a proper answer! :D
    I do actually want the LED to blink at HD activity.

    I'll get my multi meter out of garage tomorrow and see if it has current readings capability. Thanks again for the replies guys!
     
  9. BMorse

    Senior Member

    Sep 26, 2009
    2,675
    234
    Normally there would already be a current limiting resistor in the circuit for the original LED that was there, so you might just be better off using a transistor to control the LED (normally I would use an optocoupler), just connect the resistor going to the base of the transistor to the wire that blinks the original blue LED when there is HDD activity......

    If you want, I can give you a circuit, which is more elaborate than just one LED and gives you an actual "activity" meter, not just one blinking LED.... check out the video here >>> http://www.youtube.com/mcscoder#p/u/25/ux6TC0doJrk


    My .02
     
  10. lmartinez

    Active Member

    Mar 8, 2009
    224
    6
    I suggest for your to read the following material:

    Thevenin's Theorem: it will assist you understand how to replace an the existing electrical part within a circuit with what you wish to replace it with. Enjoy learning...:)
     
    Last edited: Nov 25, 2009
  11. Borat

    Thread Starter New Member

    Nov 12, 2009
    5
    0
    Hey guys, thanks for your replies!!! Exam time... Makes me sad! I'll get down to theory as soon as I'm done! Once again thanks for your help!
     
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