Difference between revisions of "Light-emitting diode"

Revision as of 17:22, 26 July 2008

Light emitting diode

To make the LED light up, you need a power supply (any voltage) and a resistor.

The resistance required is as follows: R = (U_power - U_led) / I_max

Example: a LED with voltage drop of Uled=1.2V and a max current of I_max=0,020A (20mA) to be powered by a 5V DC source needs:

R = (5-1.2)/.02 = 190 ohm

You then connect a 190 ohm resistance in series with the LED to make it work.

A few people use LEDs in an unusual way: as sensors.

@@ Line 1: / Line 1: @@
-Light emitting diode:
+Light emitting diode
+To make the LED light up, you need a power supply (any voltage) and a resistor.
 The resistance required is as follows:
 R = (U_power - U_led) / I_max
-Example a LED with voltage drop of Uled=1.2V and a max current of I_max=0,020A (20mA) to be powered by a 5V DC source needs:
+Example: a LED with voltage drop of Uled=1.2V and a max current of I_max=0,020A (20mA) to be powered by a 5V DC source needs:
 R = (5-1.2)/.02 = 190 ohm
@@ Line 10: / Line 12: @@
 You then connect a 190 ohm resistance in series with the LED to make it work.
+== sensor ==
+A few people use LEDs in an unusual way: as [[sensors]].
+== further reading ==
+LEDs used normally: to emit light:
+http://en.wikipedia.org/wiki/LED
+LEDs used "in reverse": as light sensors:
-http://en.wikipedia.org/wiki/LED<br>
+*[http://www.ladyada.net/forums/viewtopic.php?p=22251  Hack a MiniPOV3 for IR capture]
+*[http://www.robotroom.com/ReversedLED.html Making an Amplified Color Sensor from an LED and an Op Amp]
+* [http://www.redrok.com/electron.htm#led1 LED1 LED Sensor Relay Tracker Schematic]