My very first LED

My first encounter several decades ago with a pillar of modern technology yielded more than just one lesson.

NEREM 1967 was the IEEE Northeast Electronics and Engineering Meeting held at the Sheraton-Boston Hotel and the War Memorial Auditorium in Boston, MA, from November 1 to 3, 1967. I was there, although most of the engineering population in the Northeastern United States could probably have shared that claim back then; it was perhaps the busiest mass of human activity I’ve ever encountered in one common environment.

The display booths were extremely elaborate, but the one thing I couldn’t help noticing was that all these demonstrations of test equipment sported a constellation of these strange but intense little red lights that, in many cases, formed numbers, but some of which had to be viewed from pretty much straight on or the light would vanish.

Of course, they were early versions of LEDs.

Shortly afterward, having learned what an LED was, I obtained a sample. It was a Monsanto type MV-50 (Figure 1), which, when I wired it up, I saw its little red light. At the same time, a separate light of realization went off in my head as I finally understood what it was that I’d been seeing all over the place at the NEREM show.

Figure 1 My very first LED obtained soon after attending NEREM 1967. Source: eBay

Next, I began studying some LED datasheets.

One parameter that kept appearing at the forefront of many datasheets was light output rated in candelas. The candela is a unit of luminous intensity or luminous power per unit of solid angle, and the numbers for that parameter rivaled each other from product to product.

However!!

The physical dimensions of some LEDs of that era were really quite small and some of them had very directional and limited light output patterns. Even though the candela ratings could be “impressive”, the total light output from some of them was, if you’ll forgive me for being judgmental, puny.

The stress that was placed on the high intensity rating seemed like an exercise in specmanship. Still, if you want to know how far LED technology has come in the ensuing fifty-odd years, take a late-night walk-through Times Square in Manhattan and don’t forget your sunglasses.

John Dunn is an electronics consultant, and a graduate of The Polytechnic Institute of Brooklyn (BSEE) and of New York University (MSEE).

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