This is PAGE 3 of the 1960s exhibit. Go here to return to PAGE 1.




1960-1969: THE LED IS BORN





This is an old red LED, manufacturer not known (very possibly Motorola), part # NKT 7011.
A fan of the website recently mailed me two of these LEDs, and they arrived on 06-30-06.



Note that the LED has three leads, not two.
I do not know what the third lead is for; probably nothing at all.

Spectrographic plot
Spectrographic analysis of this red LED.
Ocean Optics USB2000 Spectrometer on loan from TWO-CUBED.



This is a rare General Electric SSL-6 LED, which is a yellow silicon carbide (SiC) LED. I believe these were available as early as the late-1960s.





These pictures show one of these LEDs, as owned by L.N. in Italy.
One of the emails he sent in late September 2003 simply reads:
I own 1 SSL-1 and 1 SSL-6 new in original perspex box

Note: I do not have this LED, so please don't ask me to fire it up and tell you what it looks like...sorry about that.

Thanks to L.N. in Italy for these photographs.



I received a GE SSL-1 SiC (silicon carbide) yellow LED from R.L. in South Carolina USA on 06-21-08!!!
I've been looking for one of these LEDs for years now, and I can now say that I have one!!!
Thank you very much R.L.!!!
It comes in a metal can with what I believe is a glass positive (magnifying) lens in the end.
The die appears to consist of a mainly cubical block, and its primary composition is SiC (silicon carbide); a material most people know of only as the hard, abrasive crystals used in grinding wheels and some sandpaper.



This is a 5mm of fairly recent pedigree (left) compared with the GE SSL-1 (right).



This is a photograph of it in my LED test set, being operated at a current of ~29.4mA.
You'll immediately note that this LED really isn't all that intense; its light output could probably be measured in Ácd (microcandelas).
The intensity is simply too low to measure with the instruments at my disposal.
According to the packaging materials, this LED has an output of 14 foot-lamberts at an If of 50mA.



This is the package it comes in to prove that I really have the SSL-1.


Spectrographic plot
Spectrographic analysis of this rather antique (circa. late-1960s) LED.
Baseline was artificially lowered with Photoshop to show actual spectral output.
And I had to place the LED directly against the sensor aperture of my USB2000 spectrometer to obtain any plot at all.


Spectrographic plot
Same as above.
Baseline was artificially lowered with Photoshop to show actual spectral output.
And I had to place the LED directly against the sensor aperture of my USB2000 spectrometer to obtain any plot at all.


Spectrographic plot
Same as above.
Only this time, the plot was adjusted via SpectraSuite software (included with my USB2000 Spectrometer) to be closer to full scale.
Note the *VERY FAINT* line at 393.9nm in the near-ultraviolet region of the spectrum. This line was not evident with quiescent conditions, so it had to be generated by this LED. Let's take a closer look at it...

Spectrographic plot
Here is the near-UV line itself; the spectrometer's response band was narrowed to a range of 390nm to 400nm.


Spectrographic plot
Same as the plot above the last one; spectrometer's response band narrowed to a range of 490nm to 720nm this time.


Spectrographic plot
The If was 50mA (its rated current) for this analysis.


Spectrographic plot
The If was 50mA (its rated current) and newer software settings were used for this analysis.


This is PAGE 3 of the 1960s exhibit. Go here to return to PAGE 1.





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