solarwind wrote:
> The most annoying thing about placing LEDs on your breadboard for pin
> status indication is that you need a resistor to go along with it.

Oh gimme a break.  Adding a single resistor to a board is both trivially
easy and cheap.

> Why don't they just build the resistor right into the LED
> so it makes everyone's life easier?

Everyone's?  Are you sure?  Did you ask everyone?  I don't remember you
asking me.  For someone that is early in learning electronics it is a good
idea to start out assuming things are as they are for a reason, and if it
doesn't appear to make sense at first glance that this is probably because
you don't understand the reason rather than everyone else missed something.

LEDs are made with different processes than resistors.  Integrating a
resistor in a LED probably costs more than for you to put a separate
resistor on your board.

Then the market for such a LED would be more limited.  Now you have to drive
it with a specific voltage to get full brightness.  Without a resistor you
can chose the external resistance so that the same LED can be used in 3.3V
circuits, 5V circuits, or others.

You don't always want to drive a LED at its full rated current.  Most
ordinary LEDs are rated for 20mA continuous current to get full brightness.
Today's LEDs are bright enough that I often run them at 10mA or even 5mA
depending on other particulars of the product.  To cater to this and the
variations in drive voltage, a manufacturer would have to have variants of
the same LED with different resistors.  This would drop the volume and
therefore raise the price even more per unique part.

Sometimes LEDs aren't driven with series resistors at all.  The driving
circuit can already be a current source and you don't want a resistor in
series.

> Do such products exist?

Actually they do because in some niches they can make sense.  Go look around
and you will find the selection far more limited than for bare LEDs, and the
price much higher.


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