2014-04-04 Nichia 225 LM LEDs

I received  box in the mail yesterday and opened it up to find a small plastic bag with the LEDs in it. The bag took up less than 1 tenth of the space inside and the rest was wadded up paper.  Each LED is in a cup in the plastic tape, and covered with clear plastic film, which peels off to allow the LED to be picked up by the automated machine that puts it on the circuit board.   In other words this is a surface mount LED. According to goldmine-elec.com, these are new Nichia NS6W183RT 6 chip SMD white LEDs, 5 mm square by 1.35 mm high. Their brightness is 225 Lumen, 73 CD, 3.3 watt, and require 21 volts at 115 milliamps.

It looks like one contact is the heatsink for the LED chip, so it should make good thermal contact with the circuit board. How am I going to mount this temporarily so that it makes good thermal contact with the mount? If it’s going to put out a lot of light it’s going to need a good heat sink. I was thinking of using a heavy copper wire as the mount. Or maybe an old copper penny? I have enough LED’s so I can experiment a little bit, so I guess that’s what I’ll have to do.

The LED has no lens, it’s just flat on its surface so the light output is over a wide area, probably close to 180 degrees. It will make a good task light over a table or something like that. But if I want to use it for a flashlight or something similar, it’s going to need a reflector. I have a lot of old flashlights with incandescent bulbs so I could try putting the LED into one of those reflectors. The problem is that those reflectors were made for incandescent bulbs, not for LEDs, and the reflector doesn’t do a good job; much of the LED’s light is spread out and doesn’t get concentrated into the beam. So the flashlight is going to look more like a flood light than a flashlight.

I heated up my soldering iron and found a piece of 12 gauge wire about 6-1/2 inches long. I took a utility knife and stripped off the insulation, then bent it in half like a hairpin and with a pliers, made the bend very sharp. Then I bent the sharp bend 90 degrees to the wires so the wires will face to the rear of the LED.

I used a forceps to hold the LED but it sprang loose and flew into some boxes on the shelves and I gave up trying to find it after about 20 minutes. I had better luck with the second one; I managed to get it soldered onto the heavy wire. But when I was soldering the other contact on, it pulled loose – I now had two LED pieces – so I found out these LEDs are very delicate. I put a rubber band on the end of a long nose pliers to hold it closed and better grip the LED. I repeated this sequence again: the 3rd led flew off into the boxes and I took a quick look and gave up. I managed to get the 4th led soldered to the heavy wire but then it broke off when I soldered the other lead on. Man, these things are really delicate! Finally I got the fifth LED on the heat sink and the other wire soldered up to it. Only one out of five! I’m really glad I bought plenty of these things!

I clipped the power supply leads and turned the power supply on and started turning up the voltage. I got to 16, 17, 18 volts and it started glowing, then got brighter. The milliammeter started to approach 50 then100 milliamps at 19.4 volts. That’s almost 2 watts. The bright white light was blinding; it lit up the bench nicely. The heavy copper wires got so warm near the LED that it stung. They were warm at the far end, so they’re doing their job.

Whew! Success! I think it’s time for a break! It’s apparent that these LEDs were made to be mounted on a single piece of PC board that puts no tension on the two contacts. I strongly urge anyone to use a similar mounting method, or you’ll get the same bad results that I got. I’m going to try a piece of PC board with a large area of copper, double sided. I may try to mount this PC board on an aluminum heatsink.

More hopefully good results later.