Is there in existance, an LED that can have its colour output controlled by varying input frequency.?

Question

ie, by varying the input frequency to a self contained LED, the wavelength of the output will change. Rather than control of a red, green and blue LED, or RGB LED seperately

Answer 1

I've not heard of one, but you could make a rather simple circuit the would provide a frequency dependent trigger to different colored diodes for the same effect using capacitors and by pass filters.

Answer 2

No.  A diode is a DC device and cannot be affected by frequency.

There are two-color LEDs that are two diodes back to back so that one polarity produces one color and the other produces another color.  These can be made to produce a third color by applying AC so that both diodes are illuminated.  But it's not really the same thing.  You can only get a third color and the frequency is not critical.

Answer 3

Charcind is correct, but it's an interesting question.  You might be able to change the colour by feeding the light from the LED into a non-linear optical medium whose properties can be varied electrically, but don't ask me for any technical details.

Answer 4

No LED, but if you want a color organ that shows different colors with varying frequency, they are available in electronic shops - see Radio Shack etc. Or you could put a graduated varying color filter from photo shops onto the screen of an oscilloscope.

Answer 5

Fairly sure it can't be done within a single LED, without changing the materials used in the LED

You SHOULD be able to get a slight colour shift using the Doppler effect, IF you can get the LED moving fast enough. Only have the LED on when its "moving" in the appropriate  direction, and at the correct speed.

Don't know the mechanics of how fast quartz changes shape, when you apply a voltage, but it's probably fairly fast. Problem would be the distance travelled is tiny, so the LED would have to be turned on/off REALLY fast.

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It would probably be easier if you could move the active part of the "junction" without moving the physical device. Perhaps limit/move the area over which the junction emits light, perhaps by altering the path of the current using the hall effect? Problem is then you'd be looking at a "bar" of light moving back and forth across the device. Perhaps a mirror at 45% aabove the light emitting surface would allow the Doppler effect, as the light emitted by the device would then be moving back and forth in the same direction as the "main" beam.

Answer 6

LED's in the old days were made of simply doped silicon, using processes that were suited toward making IC's. Now, it looks like silicon LED's are not even made anymore. The various materials used to get different colors are not well suited to making IC's. Thus, LED's tend to have only the LED.

However, you can add a 50 cent microcontroller with 8 leads to do what you want. They have single chip with onboard clocks, and are fully programmable, so you can change the limits and  patterns as needed. If the LED's are powerful, you would also need 3 transistor drivers, maybe all three in a single package. You would have to look at how to interface to the ucontroller. You could use a counter to determine the input freq, or analog circuitry if you have to be fancy. You could also use some serial or other input. Changing the duty cycle on the three output pins changes the colors. These parts put together, probably with a decoupling cap on a small section of printed circuit board, together form the module you want.

Here's this type of design:

http://picprojects.org.uk/projects/rgb/

http://www.semifluid.com/?p=12

This one is fancier:

http://www.rgbled.org/RGBLED/index.html

There are multi-chip modules put together with LED's such as this one:

http://www.superbrightleds.com/specs/rgb...

This technology could do what you want, but I could not find your function in one piece.

Answer 7

no

Answer 8

No, there is no such thing. Even the multi-colour leds have 3 led chips inside them - red, green and blue, and the different colours are made by mixing these three colours.

It is not possible in principle to do this, because the wavelength emitted by a led is determined by the energy lost by electrons as they cross its PN junction. This depends on the chemistry of the semiconductor materials, so it is a fixed value.