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Thread: [RESOLVED] Help with LEDs for power and hard disk access.

  1. #1

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    Resolved [RESOLVED] Help with LEDs for power and hard disk access.

    I am building a custom case and I want to use one of these bulgin switches for the power switch. They come in single and dual LED flavours and I would like to use a dual version but I'm a bit unsure if they are compatible with my system panel connectors.

    The literature does not clearly indicate the terminal layout of the dual versions. I think they use a common ground .

    There is circuit a diagram provided...
    Name:  Bulgin switch led circuit.png
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Size:  2.8 KB

    My mobo manual does not give much away...
    Name:  system panel diagram.PNG
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Size:  12.3 KB
    I understand the voltage is 5v and I won't need an inline resistor in the circuit. Does that sound right?

    Cheers folks.



    EDIT: I did not really ask a question there.

    Is it possible to wire the switch to indicate power and hard drive activity if it does indeed use a common ground?
    Last edited by Milk; Sep 22nd, 2013 at 11:16 AM.
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  2. #2
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    Re: Help with LEDs for power and hard disk access.

    The diagram means you have a bi-polar 2-color LED, or 2 LEDs lashed up to work like one. These need to be driven by a circuit designed for them.

  3. #3

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    Re: Help with LEDs for power and hard disk access.

    Appreciated

    In which case I think I will get the single LED version and use a separate indicator for the HDD.

    Can you confirm whether I should use an inline resistor or not. I am led (pun intended) to believe my mobo will sort that out with its black smoke.
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  4. #4
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    Re: Help with LEDs for power and hard disk access.

    You need to look at the voltage of the signal and the type of LED. LEDs vary in voltage by color, it's just how they work. Usually a case LED already incorporates the necessary voltage dropping resistor or a slightly more complicated driver circuit.

    That spec sheet for example mentions which models have a resistor built in and others where you must supply one.

    See Choosing The Resistor To Use With LEDs

  5. #5

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    Re: Help with LEDs for power and hard disk access.

    I've been thinking about using the bipolar LEDs again.

    I found an example circuit for driving bipolar LEDs which seems okay here.

    Combining the above with google, the gimp and my lack of electrical knowledge I came up with this...

    Name:  bipolar circuit 2.PNG
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    which shows the HDD circuit on the left and the PWR circuit on the right.

    Am I on the right lines? I have enough information from the article to work out the resistors.

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    Re: Help with LEDs for power and hard disk access.

    You might even find such a thing for sale as a driver IC in a small package. Looks about right to me though.

  7. #7
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    Re: Help with LEDs for power and hard disk access.

    if i were building this, i would use a led with three pins. they allow individual color control but you can still use a simple circuit to control both like this image shows.
    http://www.scienceprog.com/wp-conten...a_inverter.PNG in any case, all you really need is one tri-pin led and two resistors although you would have to be aware that the hard drive color would become the color the led is with both colors turned on. Be also aware that most bi-color leds will only accept positive voltage on one of the two color pins at a time.
    Last edited by Lord Orwell; Sep 28th, 2013 at 02:03 AM.
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    Re: Help with LEDs for power and hard disk access.

    Cheers.

    I've gone and bought the components now for the above bipolar circuit, it is a little over the top for a flashing light but I'm enjoying learning about it.

    I'm using a opto mosfet thingy for the relay. I'll post the result when I get round to sticking it all together.
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    Re: Help with LEDs for power and hard disk access.

    Job done.

    Name:  finished circuit sml.jpg
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    Thanks for the input chaps.
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