Difference between revisions of "Light-emitting diode"
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A few people use LEDs in an unusual way: as [[sensors]]. | A few people use LEDs in an unusual way: as [[sensors]]. | ||
| + | == 5.0v - 3.3V voltage drop via red LED == | ||
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| + | The average red LED has a 1.7V voltage drop. This property can be (ab)used to power very small 3.3V IC's from a 5.0V power supply -- put the LED in series with the 5V line. | ||
== further reading == | == further reading == | ||
Revision as of 13:41, 16 October 2012
A light emitting diode is the most popular kind of optoelectronics.
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.
POV
throwies
Several other wiki discuss how to turn LEDs into "throwies":
- Cybords wiki: Throwie Talkie: A Talkie is a Throwie that has been hacked to blink graffiti messages in Morse code.
- TagRecord.com Wiki: Led throwies
- the mayowiki: Throwies
sensor
A few people use LEDs in an unusual way: as sensors.
5.0v - 3.3V voltage drop via red LED
The average red LED has a 1.7V voltage drop. This property can be (ab)used to power very small 3.3V IC's from a 5.0V power supply -- put the LED in series with the 5V line.
further reading
LEDs used normally: to emit light:
http://en.wikipedia.org/wiki/LED
LEDs used "in reverse": as light sensors:
