12V LED

Discussion in 'Electronic Basics' started by [email protected], Apr 8, 2005.

2. James BeckGuest

Sounds like it has the resistor already in there, so no, you don't need
to add one. That is assuming the RS info is correct.

Jim

3. Lord GarthGuest

In typical Rat Shack style, they don't really tell you what you need to know
BUT, no LED
I have ever seen drops 12 volts in forward bias (Vf). So this unit has a
dropping resistor
in the package which looks like you can see it through the case.

Don't let these guys rip you a new one! That red LED and resistor is poor
quality at best
50mcd at 45 degrees. Their cost is probably all of 2 cents. Get an LED
from some
broken item and connect up a scavenged resistor. The color of the LED makes
all the
difference to the Vf and that's the number needed to calculate the value you
need. For just
a quick test, pop on a 470 Ohm resistor and hook up to your 12 volts. WATCH
the
polarity, it is a DIODE after all!

470 Ohms is yellow violet brown

4. Bob EldredGuest

Pay attention to this very complicated answer: NO! No resister is needed.
rated for the required voltage, in this case 12VDC. There are versions of
these lamps that have a diode and resistor for 120VAC, directly, no external
components.
Bob

5. petrus bitbyterGuest

Checking out the URL you provided, I found this component to have a build in
680Ohm resistor already. So you can connect it parallel to the 12V fan. Be
sure to connect it in the right direction. You may blow it it you connect it
in reverse.

petrus bitbyter

6. John SmithGuest

" Be sure to connect it in the right direction. You may blow it it you
connect it in reverse."

Why? Surely no current will flow, as the diode part of LED comes into play.
What's going to blow it?

7. petrus bitbyterGuest

Most LEDs can handle a maximum reverse voltage of 5V. So unless some
precautions are taken, the LED wil get 12V reverse voltage which it cannot
stand. Precautions may be a antiparallel diode or even a second LED
antiparallel to the first. As I did not see this or any other provision
mentioned in the specifications I advise to stay on the safe side.

petrus bitbyter