Post : Writing on LEDs with a laser pointer
URL : http://hackaday.com/2012/07/27/writing-on-leds-with-a-laser-pointer/
Posted : July 27, 2012 at 11:01 am
Author : Brian Benchoff
Tags : led, LED display, led matrix, light sensor
Categories : led hacks

http://hackadaycom.files.wordpress.com/2012/07/led.png

After [Ch00f] got his hands on an 8x8 LED display, he didn't make a 64-pixel video game or VU meter. He made a laser doodler (http://ch00ftech.com/2012/07/26/the-laser-doodler/) , allowing him to draw on this display with only a laser pointer.

Using LEDs as light sensors is nothing new; [Forrest Mims III] discovered that LEDs can also detect light (http://en.wikipedia.org/wiki/Forrest_Mims#Using_LEDs_as_narrow_band_light_sensors) Â way back in the late 60s. [Ch00f] played around (http://ch00ftech.com/2011/11/16/ldds/) with this concept before creating a circuit that uses an LED as both a light emitter and sensor that reacts to the ambient brightness.

[Ch00f]'s laser doodler takes this phenomena and applies it to an Adafruit bicolor LED matrix (http://adafruit.com/products/458) . When a light shines on an individual pixel in the display, the ATMega48 senses the current and turns that pixel on. Since this these pixels have two colors, [Ch00f] used a latch circuit and a button to cycle between what color the 'Mega writes to the display.

In the video after the break, [Ch00f] shows off his display by having the LEDs light up in response to a laser pointer. It may be a bit small, but we can see a lot of potential for something like this as a gigantic art installation.

Read more of this post (http://hackaday.com/2012/07/27/writing-on-leds-with-a-laser-pointer/#more-80825)

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