pier Posted May 4, 2007 Author Report Share Posted May 4, 2007 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 ? Quote Link to comment Share on other sites More sharing options...
audioguru Posted May 4, 2007 Report Share Posted May 4, 2007 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. Quote Link to comment Share on other sites More sharing options...
pier Posted May 14, 2007 Author Report Share Posted May 14, 2007 Hello AG What is lumens and CCT with respect to LED ? Quote Link to comment Share on other sites More sharing options...
audioguru Posted May 14, 2007 Report Share Posted May 14, 2007 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. Quote Link to comment Share on other sites More sharing options...
pier Posted May 15, 2007 Author Report Share Posted May 15, 2007 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 . Quote Link to comment Share on other sites More sharing options...
audioguru Posted May 15, 2007 Report Share Posted May 15, 2007 Hi Pier,If you used thermal grease between the LED and your little heatsink then it is fine. Without thermal grease then the LED is probably too hot inside.I don't know what is "hylem". Quote Link to comment Share on other sites More sharing options...
pier Posted May 15, 2007 Author Report Share Posted May 15, 2007 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 . Quote Link to comment Share on other sites More sharing options...
pier Posted May 16, 2007 Author Report Share Posted May 16, 2007 I spelled it wrong . It was hylam instead of hylem . Here is a pic of switches and a socket fixed on a hylam board . Quote Link to comment Share on other sites More sharing options...
audioguru Posted May 16, 2007 Report Share Posted May 16, 2007 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. Quote Link to comment Share on other sites More sharing options...
pier Posted May 17, 2007 Author Report Share Posted May 17, 2007 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) . Quote Link to comment Share on other sites More sharing options...
audioguru Posted May 17, 2007 Report Share Posted May 17, 2007 I use solid 22AWG wire for most low current wiring and stranded 22AWG wire for flexible wires. Quote Link to comment Share on other sites More sharing options...
pier Posted May 23, 2007 Author Report Share Posted May 23, 2007 Hi AG Should I use any protection for the transformer from AC mains voltage fluctuations or will that effect the circuit ? Quote Link to comment Share on other sites More sharing options...
audioguru Posted May 23, 2007 Report Share Posted May 23, 2007 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. Quote Link to comment Share on other sites More sharing options...
pier Posted May 23, 2007 Author Report Share Posted May 23, 2007 A reasonably high voltage is also fine. How much could this voltage be ? Quote Link to comment Share on other sites More sharing options...
audioguru Posted May 23, 2007 Report Share Posted May 23, 2007 Hi Pier,I think a transformer is designed to allow a 10% mains over-voltage. Quote Link to comment Share on other sites More sharing options...
pier Posted May 25, 2007 Author Report Share Posted May 25, 2007 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 . Quote Link to comment Share on other sites More sharing options...
audioguru Posted May 25, 2007 Report Share Posted May 25, 2007 Are your LEDs manufactured by a major semiconductor manufacturer? Quote Link to comment Share on other sites More sharing options...
pier Posted May 25, 2007 Author Report Share Posted May 25, 2007 No AG, its a chineese make. Quote Link to comment Share on other sites More sharing options...
audioguru Posted May 25, 2007 Report Share Posted May 25, 2007 No AG, its a chineese make.Hee, hee, hee. ;D ;D ;DI bought a bag of 100 LEDs made by Fairchild. Every one is absolutely perfect and they were a pretty good price. Quote Link to comment Share on other sites More sharing options...
pier Posted May 25, 2007 Author Report Share Posted May 25, 2007 Do you have the part number to order for the led's made by fairchild . What price you bought it for ? Quote Link to comment Share on other sites More sharing options...
audioguru Posted May 25, 2007 Report Share Posted May 25, 2007 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. Quote Link to comment Share on other sites More sharing options...
ante Posted May 26, 2007 Report Share Posted May 26, 2007 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 Quote Link to comment Share on other sites More sharing options...
pier Posted May 26, 2007 Author Report Share Posted May 26, 2007 will i be able to get LED's which are similar to each other, i mean from big branded manufacturers ? something like led's from a batch ? Quote Link to comment Share on other sites More sharing options...
audioguru Posted May 26, 2007 Report Share Posted May 26, 2007 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. Quote Link to comment Share on other sites More sharing options...
pier Posted May 26, 2007 Author Report Share Posted May 26, 2007 Hello AG What was the part number you gave ? Quote Link to comment Share on other sites More sharing options...
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