LED

[Eddie Arnold]

Yes , it is true . you must use a limiting resistor.

Example : 5 volt source and a typical led which runs at 1.2 volts and 10
ma. needs a 380 ohm resistor.
hope that helps

http://nettacker.com/

Tomy wrote in message <7q8vim$k8s$1...@imsp009a.netvigator.com>...
>Hello,
>
> How can i run my LEDs safely? I 've heard some people said that LED has
>to be ran with some other components in order to use it for a long time
>withour
>burning. Isn't it true? Anyone can help me please.
>
>Tomy
>t...@hkstar.com
>
>

[Tomy]

[bruce]

the answer - a resistor

Tomy <t...@iname.com> wrote in message
news:7q8vim$k8s$1...@imsp009a.netvigator.com...

[spark builder]

Considering that you are running the LED off of a stable DC voltage supply, all
that you need is a resistor in series to the LED for limiting the voltage to
below max. spec. based on the LED's impedance. If the supply fluctuates (like
AC), however, then you've got some difficulties.

[Lord Garth]

Psssst! Resistors limit current !

spark builder <ga...@ufl.edu> wrote in message
news:37C822FA...@ufl.edu...

[Robert]

Nothing very complicated about LED's. Here are the basics:
Limit the current flow through the LED using a resistor. Calculate the
resistor as follows:
( Supply voltage - forward voltage of led ) / current through LED

Forward voltage Red LED = 2V, Green = 2.3V, Yellow = 2.2V, Blue = 3V, White
= 3.6V.
Current through LED: usually between 10 and 25mA for most applications.

Worked example: for supply = 5 Volts, current at 20mA (0.02A) and a green
LED, resistor = (5-2.3)/0.02 = 135 ohms.

Other things that damage LED's: They don't like more than about 5 volts
connected to them in the reverse direction. In the above example, if the 5
volt supply was reversed, the LED is reverse biased (no current flow). In
this condition there is no voltage across the resistor and thus the full 5
volts appears across the LED. This is right at the limit for safe operation.

Feel free to contact me if you have any further questions regarding LED's.

Rob <ssjo...@callnetuk.com>

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[NO]

"Tomy" <t...@iname.com> wrote:

>Hello,
>
> How can i run my LEDs safely? I 've heard some people said that LED has
>to be ran with some other components in order to use it for a long time
>withour
>burning. Isn't it true? Anyone can help me please.
>
>Tomy
>t...@hkstar.com
>
>

do you mean Light emitting diodes? if so I would reccommend putting a
resistor in series with it do that the voltage that is across the LED
doesn't exceed more than 1.5V.

Joe

To get in contact with me via email, please remove the NOSPAM from the email address.

[ssjo...@callnetuk.com]

[Bill sloman]

spark builder wrote:
>
> Considering that you are running the LED off of a stable DC voltage supply, all
> that you need is a resistor in series to the LED for limiting the voltage to
> below max. spec. based on the LED's impedance. If the supply fluctuates (like
> AC), however, then you've got some difficulties.

This isn't particularly coherent. It is important to note that LEDs have
a rated
maxiumum forward current, and if you exceed it you risk blowing up the
LED.

Most LEDs are specified at a forward current of 20mA, and the data sheet
will
specify minimum, maximum and typical forward voltages at a current of
20mA.

This voltage can range from 1.2V for some red LEDs, to 4.0V for some
blue LEDs.

You need to chose a resistor that will limit the current through the LED
to
less than the rated maximum when your supply current is at its maximum
(5.25V for
a nominally 5V supply, say) and the LED forward voltage is at its
minimum.

The LED data sheet also specifies a maximum reverse voltage - often
around
5V. If you reverse bias a LED by more than this voltage, it may light up
-
and I've seen this used to get very fast rise-times out of an LED - but
you risk destroying the LED.
Bill Sloman, Nijmegen

[Alan Middlemas]

Tomy
A LED has a foward drive voltage ( Vd ) of 1.6 V D.C.
Most LEDs need a drive current ( Id ) of .010 A or 10mA.
There must be a limiting resistor to protect the LED

Bat--------/\/\/\-------->I-------GND
5V------- resistor -------LED-----GND

EX:1
If for example you wish to run a LED on a 5 V digital circuit then follow this.

5V - Vd (1.6) =3.4V
Id = 10mA
Using Ohms Law
R=Vd/Id
3.4V/.01 = 340 ohms

now the common resistor near this is 330 ohms.

EX:2
If for example you wish to run a LED on a 12V car battery circuit then follow
this.
12V - Vd (1.6) =10.4V
Id = 10mA
Using Ohms Law
R=Vd/Id
10.4V/.01 = 1040 ohms

now this common resistor near this is 1000 ohms or 1K ohm
good luck
Alan

[Graham Knott]

look at http://ourworld.cs.com/gknott5413/elect112.htm
electronics for beginners
http://ourworld.cs.com/gknott5413