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Thanks to our Technology Editor Steve Bush for flagging this one - Build a DIY LED - which continues the LED theme nicely, following our Build your own LED cube post.It is a fascinating article by one Michael T. Lippert about making a light emitting diode from a pin and the mineral Moissanite.
He states that this is Silicon Carbide or Carborundum (compound of Silicon and Carbon - SiC) and that he used a less rare synthetic form of it:
Most of you will know this substance as the black "sand" splinters on sand paper. Due to its extreme hardness it is most often used in abrasive substances and tools. You could easily cut glass with it. I picked up four boxes with 1 cm big crystals for one Euro total on Ebay.He was inspired by reading a biography of Oleg Losev, described as the inventor of the LED, and an article in Nature:Photonics describing the history of the LED.
He continues:
The setup is very simple. I took a crystal of SiC and attached a clamp to it to supply it with about 20 Volts. It is important that the plus clamp is used. It is further advisable to limit the current to something around 30 mA. This will prevent the crystal from heating up too much, as the diode forward voltage will be only on the order of 9 Volts @ 30 mA.For full details see: http://www.dlip.de/?p=99
If you have no current limiter on your power supply or want to use a battery, use 12 Volts as fixed voltage and be careful not to overheat your setup. The negative lead is attached to a wire which holds a regular pin from your sowing supplies. After applying the voltage the pin should be moved across the surface forming a cat's whisker detector. Every now and then a tiny light appears at the contact point. This is the LED!
Comments (4)
I made a light emitting diode back in the 1960s by accidentally passing far too much current through a germanium point contact diode and getting the tungsten wire to glow!
Posted by EW | December 9, 2009 7:05 AM
Posted on December 9, 2009 07:05
I like it, Erich. I wonder how many other "accidental" LEDs have been created out there?
Posted by Alun Williams - Electronics Weekly.com
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December 10, 2009 10:45 AM
Posted on December 10, 2009 10:45
EW's comment above, while strictly a glowing diode, is only glowing because of resistive heating of the fine wire contact rather than by light emission from the diode due to electron/hole recombination.
I have heard of carborundum emitting light - thanks for giving more details! Methinks an opportunity to play presents itself, probably with a phototransistor and a modulated supply to measure turn-on/turn-off times too!
Posted by Peter F Vaughan | May 11, 2011 12:20 PM
Posted on May 11, 2011 12:20
is only glowing because of resistive heating of the fine wire contact rather than by light emission from the diode
Hey, light is light ;-)
Glad you enjoyed the post, Peter - a "chance to play" should always be embraced, I think!
Posted by Alun Williams - Electronics Weekly.com
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May 12, 2011 4:30 PM
Posted on May 12, 2011 16:30