What is a Diode?

According to google

"[size=-1]A device that allows current to flow in one direction only."

Light Emitting Diode?
Laser Diode
Diode on a Circuit board

While looking for "diode" on ebay I just this second found this lol

http://cgi.ebay.com.au/Solar-Centurion-Light-Emitting-Diode-Floodlight_W0QQitemZ7765032355QQcategoryZ20509QQrdZ1QQcmdZViewItem

It's an LED Floodlight (Solar Powered) for Outside, pretty cool idea

but back to Diode... and what a Diode is, why is an LED or Laser Diode called a Diode, if a Diode simply passes /electricity/ through on a Circuit board..

probably going no where on this lol, anyone like the Flood Light?

[/size]

LED stands for Light Emitting Diode.

Not all LEDs are lasers but some are.
Not all lasers are diodes but some are. (ho hum? Is this right?)
Not all diodes are LEDs but some are.

Diodes were initially developed to allow the passage of electric current in one direction whilst blocking the flow of current in the other(he blithely writes without research). A bit like a one way valve or gate. They can be used to make alternating current(AC) into direct current(DC). Other sorts have properties that allow them to be used to regulate voltages (zenier) diodes. Stick two diodes together in the right way and you have a transistor. Stick a few transistors together and you have a Cray supercomputer.

Have a look at "crystal radios" link if you want to play with one without any battieries.

And some bright spark found that they could also emit light. Thank you. Thank you. Thank you. Thank you. Thank you. Thank you. Thank you. Thank you. Thank you. Thank you. etc. etc...


Here are the Wiki links.
Diode
LED
Laser

Or if you really, really like them go and study physics.

Regards

Diodes are a electrical valve. They are made up of two sections of silicon (or germanium) that have different impurities in them laid side by side. One section has an extra electron and the other side needs an electron. This allows the electrons to flow much more easily in one direction than in the other. LED's are diodes that produce light as a biproduct of the forward flow of electrons. Its an inefficiency, sort of. As the electrons flow "downhill" they product light and heat rather than just heat. The color of the light is determined by the chemistry.

Hope that helps.

How Stuff Works . com

(an article on how LEDs work)

This site is great for everything! (I also recommend their article "How Skydiving Works.")


-Jeffrey

Good call peacefuljeffery!! That web site howstuffworks.com is the best at explaining stuff. I could waste 2 days easy, just reading on that web site.

kendallAA

lol, how true i must say i've used that site a few times

And thanks to leduk for trying

Well, just to pick a few nits - a Diode is, as various people stated, a device that conducts differently, depending on the direction of the current. Most diodes will conduct in their reverse direction, but usually the conductance in one direction is better by a few orders of magnitude compared to the other direction.
But, unlike what most people (and the first pages of howstuffworks) said, a diode doesn't have to involve a semiconductor. Actually, semiconductor diodes are pretty complicated if you really want to know how they work (unfortunately, both LEDs and laser diodes are semiconductor diodes).
The simplest diode (in terms of understandability) is still the vacuum diode: imagine an empty (i.e. vacuum) container (usually a glass tube, but that's just because they're easy to make and fill with vacuum). Add two electrodes - basically, they're both the same at the moment - which are not touching each other. Now, at room temperature, you can apply quite some voltage between the electrodes without anything much happening (this is why we use a vacuum - if the container were filled with gas, things would be different - you'd get a HID...). This changes when you heat up one of the electrodes: this will enable some of the electrons on this electrode to escape from the metal - and since we have a voltage applied between the electrodes, the electrons will be accelerated towards the positively charged electrode. If this happens to be the hot electrode, you gained nothing much -the electrons will simply return to where they come from, still no current flowing between the electrodes. But if you apply the positive charge to the cold electrode, a current will flow from the hot, negative cathode to the cold, positive anode - you have a diode!
Admittedly, vacuum diodes are a bit unwieldy when it comes to most of today's applications, but for some special cases (high-end audio and high voltage handling) they're still in use.

Bye
Markus