On Fri, 16 Feb 2007 04:53:13 GMT, Thomas Horne
wrote:

Chop Suey wrote:
Larry inspired greatness with:

The LEDs being produced today for illumination do not require any resistor.
They are connected directly to the battery or other power source.


They may have a resistor packaged with it, but a LED is a *DIODE*, and
it requires a resistor.


For the sake of my education let me ask. Doesn't an LED have a
predictable voltage drop across the junction? I seem to recall 1.5
volts is that correct?

It varies depending on the LED. In an electronics catalog I got last
year, I see forward voltages ranging from 1.5V to 4.8V (that high one
was blue). I'd expect it to be constant for a particular LED.

If it is I only need as many LEDs in series as
will equal the voltage and they will need no external resistance. Is my
memory wrong?

Maybe if that voltage is EXACTLY right. Theoretically, you might see
this a few times during the life of the universe. In reality, don't
expect it.
--
Mark Lloyd
http://notstupid.laughingsquid.com

"Unlike biological evolution. 'intelligent design' is
not a genuine scientific theory and, therefore, has
no place in the curriculum of our nation's public
school classes." -- Ted Kennedy