LEDs Part 2

In my previous post, I went over how I selected the Lite-On LTST-C230TBKT blue LED. Today I'll discuss the process I used to check that this LED was a good selection.

The first thing I did was go to Octopart to see what prices and availability were like outside of Digikey. There, it looked like Digikey had the best price and the most in stock, but Mouser had 10,000, and a few other places also had these LEDs.

Second, I wanted to see what other color options existed in the same form factor and with similar electrical characteristics. Down at the bottom of the Digikey product page is a link to view the product in the online catalog.

There, I saw a bunch of color options, which looked promising. From that page, there is a link to view results as a parametric search. There were some non-reverse mount LEDs and multiple packages. After selecting only reverse mount, cut tape, and in-stock parts, there were nine options left (about one in each color). I could have red, amber, yellow, green, or blue LEDs. They all had the same current rating, so the current set resistor connected to the LED driver IC wouldn’t need to change. Because they all had the same package dimensions (which presumably meant that the land patterns for the PCB were the same), I could use the same PCB for any color.

Next, I wanted to see the options for buying reels of these LEDs. Digikey has a nice little "Alternate Package" box with a link to the reel packaging. At 11,000 LEDs, they would cost just under $0.07 each. If I built more than 500 boards and ordered more than 15,000 LEDs, that price would drop down closer to $0.06. That price was not bad and was a lot cheaper than other options I'd seen.

Finally, I wanted to check the datasheet. LEDs are simple, but I like to know that the manufacturer cares enough to test the product and publish the results. For this project, some of the exact details don't matter, but it's nice to know the product is well characterized. It's reassuring to have the spatial distribution of the light produced, for example, even if I don't need that data at this point. More importantly, the datasheet has land patterns and hole cutouts for the PCB and also has exact dimensions of the product and its packaging. The PCB information would make it easy to lay out the board. The dimensions of the reel would be useful for a contract manufacturer or assembly house so they know what they're getting and can set up their pick-and-place machines.

After I considered these features, this LED looked good. In my next post, I plan to go over my selection of the connector.