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Thread: Can someone advice the right way ?

  1. #1
    Unenlightened
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    Jun 2012
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    Default Can someone advice the right way ?

    Hi, I need to replace a 14" tube-light (working on 230v ac / 50 hz) with a LED lamp with 35 w brightness, the new LED tubelight need to go into a control panel. This is my first project with LED's, and I am learning.

    My options are:

    Option 1:

    I have the capacitance based circuit that steps down the ac and drives the 96 nos. of 5 mm round white LED's. The output of the circuit provides 69 v dc @ 72 mA. The LED's are arranged in four rows of 23 LEDs each. Each row is provided with 18 mA current. The entire circuit is assembled on a PCB, and at one end, is being provided with a fan of 40 x 40 x 10 mm (230 v ac / 50 hz) for forced air circulation. What problems should I look out for ?

    Option 2:

    Other option is to use 1W LED's. I have a few of them and am unable to understand how to fix them onto the heat sink. The LED's are cicular with a dome shape and have terminals on either side (that look like small wings) for surface mount technology (my guess). The reverse of the LED has a metal tab, but my problem is that the tab is at the same plane as of the terminals. I am aware of the need for heatsink, but how do I fix them on the heat sink ?

    Comments are welcome and thanks,

    Madhav

  2. #2
    *Flashaholic* wquiles's Avatar
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    Default Re: Can someone advice the right way ?

    What are you using/planning on using to convert the AC variable voltage to a DC voltage needed for the 5mm/1W LED's? Is it a voltage regulator that takes from 230v to 69volts DC? How much ripple do you have on the DC side?

    What happens on a voltage spike, and the input voltage goes above 230V? Does the output voltage also goes up proportionally?

    Photos would help immensely, specially those of your 1W LED's.

    Will
    Please no PM/Visitor Msg's. Email for questions/Paypal: wquiles [at] gmail {dot} com. Please visit my new website.

  3. #3

    Default Re: Can someone advice the right way ?

    Quote Originally Posted by Madhavdivya View Post
    Hi, I need to replace a 14" tube-light ... with a LED lamp
    Why are you specifying LED?

    with 35 w brightness,
    Do you mean the light output of a 35 watt incandescent bulb?

    the new LED tubelight need to go into a control panel.
    Is there a way for air to flow around the light when it gets hot?

    This is my first project with LED's, and I am learning.
    Congratulations.

    and drives the 96 nos. of 5 mm round white LED's.
    There is some question in my mind about the life expectancy of the 5. MMs.

    at one end, is being provided with a fan of 40 x 40 x 10 mm (230 v ac / 50 hz) for forced air circulation.
    OK, so you do have ventilation.

    The reverse of the LED has a metal tab, but my problem is that the tab is at the same plane as of the terminals.
    What I normally do is bend the terminals up a little and stick a piece of electrical tape on the heat sink under them so they cannot touch.

    I am aware of the need for heatsink, but how do I fix them on the heat sink ?
    A technique you may wish to try is to get "Arctic Alumina" (or similar) epoxy and glue it down. The epoxy is specifically designed to conduct heat well.

    Another technique is to drill two small holes into the heatsink and use nuts and bolts to simply bolt the LED firmly to the heatsink.
    Last edited by Ken_McE; 06-09-2012 at 06:13 AM.

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