A Play on SMD LEDs

mrburnette

Senior Member
I was ordering some parts the other day from an eBay seller in the States (reseller, I'm sure his wares come from China, but the shipping was free, but I still think of it as a domestic order!) Anyway, I was about to cash-out my basket when I noticed that he had small numbers of inexpensive SMD LEDs... a couple of bucks for 20. So I ordered 4 colors in two sizes: 0603 and PLCC-2. I was pretty sure that I could work with the PLCC-2 size even with my weak eyes, but I was taking a real chance with the 0603's ... or so I thought.

As it turned out, I spent lots of time trying to find a single 0603 that jumped out of the carrier strip as I was removing it... the carriers are stiff plastic, so if you strain the plastic, the part will sail away. I have a great way to find the little buggers: Just use one of those lint rollers that are low-tack... and roll it around. Not only will it catch your lost part, it will clean up the workbench from all the little pieces of snipped wire and plastic insulation! Just remember that the roller gets highly charged with static when the tape is removed, so you will want to pass it over the anti-static mat once or twice to ensure the part does not receive ESD damage when removed.

I had a nice afternoon play with these little LED parts. I found out a few (rather obvious, I'm sure) things and I wanted to pass it on to anyone who may not have thought of it yet. First, the 0603's are the perfect size to use with scrap pieces of etched protoboard; they will bridge the copper runs nicely. I found a scrap that had the power bus along one edge and just a few plated holes. The 0603 LED perfectly bridged the gap and the next hole was used to insert a strip of 8-pin header. The last hole in the bus strip was used for a single pin, staggered 1 position back, but in-line with what would have been the 9th LED. This made a nice 9-Pin strip for an 8-Bar LED. Add a 3-8 decoder (74HC238) and you have a very inexpensive LED BAR.

The other rather obvious idea is that you can use the high-stick copper tape and create a LED area anywhere you want. If you must, use Kapton tape to insulate prior to placing the copper tape. Or use copper tape and Kapton tape to create complex runs. This works much better than it sounds!

The other nearly spontaneous idea was that the PLCC-2 is perfect to solder directly on a PIN header strip. I used two pins to attache the LED and the 2nd and 3rd pins to place the current limiting resistor. Works perfectly on the breadboard.

The JPG shows all three concepts materialized in the physical computing world. So the next time you place an order, throw in one of those inexpensive SMD LED assortment and have some bright fun... Just perfect for PICAXE stuff.

- Ray
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