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pier

white led

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Hi AG
        I have seen in the projects Q/A form, your topic on the mood lamp where in the last a heat sink has been suggested for the LED. Should we use a heat transfer paste (white colour) in b/w the LED and the heatsink ?

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Heatsink compound (the white paste) should always be used between a semiconductor's metal surface and the heatsink. It fills microscopic valleys and scratches with the compound that conducts heat very well. The film of paste must be very thin and the items should be tightly bolted together.
The LED datasheet has spec's for a heatsink.

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Hi Pier,
Ordinary small LEDs have their brightness measured in candela or milli-candela units.
Incandescent, fluorescent and very bright large LEDs have their brightness measured in lumens.

One type of measurement takes into account the different sensitivity of our vision to different colors.

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hello AG,
            I bought a new one (luxion 1 star) The Voltage across the led is exactly 3 volts with the regulator circuit . I have mounted it on to a heat sink(aluminium) of size 57mmx57mm square with 3mm thickness( i cut it myself ) and that is now having heat sinking . I want to screw the heatsink on a hylem sheet of thickness 3mm and length 100x100mm to screw it up again on the roof. Will the hylem sheet get damaged because of heat ? the tempetature on the heatsink just below and opposite to the led is 50 degree centigrade .

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Hi AG
        It is used to fix switches and sockets on them. Brown colour on the back and white in the front made by Anchor . I will try to send a pic .

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Bakelite Hylam Ltd. has made bakelite in India since 1947.
Very old phones and tube radios were made of bakelite.

Maybe now they make a newer plastic. I don't think you should have your 50 degrees C heatsink near it.

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Hello AG,
              Thanks for advice . I'll screw it up with some space in between (using lingthier screws). What wire shall i use for the led(+&-) I have used one now with 7 strands and 0.2mmthickness for each strand (here we call it 7.2 wire) . 

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A low mains voltage won't harm a transformer. A reasonably high voltage is also fine.
A gross overvoltage (lightning, high voltage by mistake or by accident) would fry a transformer.

Most overvoltage protection devices conduct to blow themselves up or to blow a fuse.

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Hi AG
        In my previous LED project 2 LED's blew off from in between the string , I think that the quality of the LED is poor . What do u think ? . I just replaced them .

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Fairchild and all the other major semiconductor manufacturers make hundreds of excellent LEDs at a good price. I recently got an e-mail from the distributor where I bought mine that mine are now discontinued and I could have bought the last ones they had. I didn't buy any more because better ones are available now.

I bought some white and blue LEDs made by Hewlett-Packard who changed to Agilent who changed to another name. They are made for pixel screens at stadiums and are also excellent.

I bought some LEDs made in your country and half of them were bad. The store replaced them all with better ones.

I bought some LEDs made in the same country as ypurs. Most were good but some  failed.

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Hi AG
        In my previous LED project 2 LED's blew off from in between the string , I think that the quality of the LED is poor . What do u think ? . I just replaced them .


As with transistors in parallel you can

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Hi Pier,
Aren't your LEDs connected in series? Then the current through each one is exactly the same and the LEDs don't need to be the same. They just need to live up to their current rating.

I bought my factory-sealed bag of 100 Fairchild LEDs online from Digikey. They were probably from the same batch.

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