Light-emitting diode

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m (LED moved to Light-emitting diode)
(LEDs used "in reverse": as light sensors (moved from sensors))
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Light emitting diode:
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Light emitting diode
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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:
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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
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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.
  
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== sensor ==
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A few people use LEDs in an unusual way: as [[sensors]].
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== further reading ==
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LEDs used normally: to emit light:
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http://en.wikipedia.org/wiki/LED
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LEDs used "in reverse": as light sensors:
  
http://en.wikipedia.org/wiki/LED<br>
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*[http://www.ladyada.net/forums/viewtopic.php?p=22251  Hack a MiniPOV3 for IR capture]
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*[http://www.robotroom.com/ReversedLED.html Making an Amplified Color Sensor from an LED and an Op Amp]
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* [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:

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