NXT colour sensor functions

[TasV]

My Son and I are struggling with getting two colour sensors (running as light sensors) to give similar values due to differences in orientation to ambient light sources. We have installed two white LEDs in front of the sensor (you can just see it in the top of the photo as a yellow spot), in the hope that if we install our own light source we can even out any variations in the readings caused by different orientations relative to the ambient light source(s) and to reduce the chances of errors being made when the robot must pass through an overhang that blocks all light from the top. It has worked quite well but in some orientations it really throws the values out too if the ambient light source is drastically different on one side than another. The effect is that they combine and throw the two sensors out by as much as 20%. So, I'm trying to understand what each of the parts of the colour sensor does so that we can maybe orient the LEDs in a more optimal position for both sensors and/or create some kind of shield in the appropriate place to prevent the sensor from 'seeing' the majority of the ambient light. This is a photo of the bottom of the colour sensor showing the different parts. I know the part on the right is the RGB LEDs and I think the part labelled 1 senses reflected and ambient light. What does the part labelled 2 do or does it measure the ambient light and 1 measure reflected light? I have looked for this information and it is eluding me.

Edited June 17, 2013 by TasV

[MikroMan]

According to this: http://botbench.com/blog/2011/09/16/exposed-lego-colour-sensor/ , the bottom indentation is just a fake, so you only have RGB LED and photo-detector cell.

[TasV]

WOW! No wonder we can't get the values to match up... one light detector faces the outside of the robot whilst the other faces the middle of it. Thank you for the help. I think I will either get some HiTechnic Colour senses or just go and get a few Lego Light Sensors instead so the lamps and sensors are in line.

[MikroMan]

No problem... I've never thought about this, but when you look at the design from this perspective, it's obvious that LEGO's former design of light sensor was way better for precision sensing like in your project. But probably they wanted the sensors to be easily identifiable, so they redesigned the front panel.

Also, here's a comparison of HiTechnic and LEGO colour sensors with their advantages and disadvantages: http://www.philohome.com/colcomp/cc.htm

[TasV]

I notice the new EV3 colour sensors are centrally aligned. I wonder if they are compatible with NXT 2.0?

[Someonenamedjon]

2 is the light reader.

Edited June 17, 2013 by Someonenamedjon

[TasV]

1 must be the light sensor: http://botbench.com/blog/wp-content/uploads/2011/09/CIMG0939.jpg

[Someonenamedjon]

1 must be the light sensor: http://botbench.com/...09/CIMG0939.jpg

Seems legit. looks like the LEDs.

I notice the new EV3 colour sensors are centrally aligned. I wonder if they are compatible with NXT 2.0?

Impossible.

Edited June 17, 2013 by Someonenamedjon

[AVCampos]

I notice the new EV3 colour sensors are centrally aligned. I wonder if they are compatible with NXT 2.0?

According to the EV3 FAQ page, you'll be able to use EV3 motors, but not sensors:

Q: Will EV3 sensors and motors work with the NXT intelligent brick?

A: All EV3 sensors are digital and therefore they will not work with the NXT intelligent brick, but the EV3 motors will work with the NXT intelligent brick.