Difference between revisions of "Light-emitting diode"

From OpenCircuits
Jump to navigation Jump to search
m (LED moved to Light-emitting diode)
(LEDs used "in reverse": as light sensors (moved from 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:
 
The resistance required is as follows:
 
R = (U_power - U_led) / I_max
 
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
 
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.
 
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]

Revision as of 18:22, 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.

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: