I would like to use the NXT light sensors my EV3 brick. I don't have enough light sensors as I need 2 for each robot (per set) and it only comes with one. However, I have a lot of NXT sensors. Will the EV3 be able to use it and is it as accurate as the EV3 light sensor?
NXT Color Sensors are supported directly by EV3-G, the EV3 software running on the PC or MAC. NXT Light Sensors are not.
To use Light sensors requires a bit of trickery. EV3-G has a Raw Sensor block that provides access to the Light sensor values. The raw sensor returns values from 0-1023, which is very different than the 0-100 of the NXT-G Light Sensor block.
Setting up the Light sensor to use ambient or reflected light is also solved with a bit of trickery. Use the Sound Sensor Block and toggle the dB setting.
Once that much is tested and working, create a set of MyBlocks to mimic existing Color Sensor blocks.
Raw sensor value works, but shows a level of dark, not of light :), meaning that higher values indicate lower light.
Ambient light works directly, but for reflected light you need to insert a EV3 Color Sensor block with Reflected Light mode to turn on the light in the NXT Sensor. After that, use raw values or the Sound sensor block.
The Sound sensor block is not included in the download version of the EV3 software (at least not in mine), you can download the necessary ev3b file from http://www.lego.com/en-us/mindstorms/downloads and then import it into your project.
The kids on the FLL team I coach created a video that explains how to use the NXT light sensors on an EV3. Hope it helps. http://youtu.be/I7Bqvk-uMLk?list=UU2r9xq9o39SbEX1cESNdIHA