what proximity sensor...?

[HaWe]

hi,
what kind of proximity sensor would you suggest to use:
distance range: 1-10 cm
detection angle: < 10°
just distance: independend from colored or black or white pieces, from background color or brightness, and from ambient light
type: i2c (if chainable, and if adjustable bus addresses, and if NXC drivers already exist), otherwise better analog

(I'm actually not sure if the HiTechnic EOPD Sensor matches the requirements)

[mattallen37]

If you don't want it to be affected by light in any way, then why not use ultrasonic? And no, I don't know of any that are made to your requirements and the requirements of the NXT, to just plug and play with NXC.

[HaWe]

yes, sure, US would be very good, but what sensor do you have in mind which matches the requirements (see TOP) ?

distance range: 1-10 cm (whole range needed at least)
detection angle: < 10° (not bigger)

[mattallen37]

I was merely suggesting a type of sensor that might work for you. And again, no I don't know of a specific one that would match your requirements. I know SparkFun and Pololu sell ultrasonic sensors (although not exactly the perfectly ideal one for you).

[aswin0]

Ultrasonisch sensors have a wide beam, something like 30 degrees. They also have a rather large error at short distances. So they will not do I guess.
The EOPD measures the amount of reflected light, so it must be calibrated for a particular surface and color. This also doesn't fit you requirements.
The Mindsensors range sensors are based on angles of reflecting light coming from the sensor. They have a narrow light beam, high accuracy and they are color and surface tolerant. They come for different ranges. I think one will meet you criteria.

[HaWe]

thanks, I know the MS sensors of course and they have already been proposed to me by mcsummation (PM), but as far as I can see none of them has got what I need - maybe you can give me a closer hint?

[aswin0]

I would take the short range version. Its range is 4 to 30 cm. if you enlarge the distance between sensor and object just a few cm then your specs will fall within the range of he sensor. Check out the data sheet for full specs.

Oh, and when using this sensor make sure to put it off from within your programs whenever possible. It takes a lot of fuel.

[HaWe]

no, I can't enlarge the distance, I need it from 1 cm to 10cm.
But AFAIK from my Sharp GP2D12 and GP2D120 distance sensors the detection angles are also far bigger (estimated 30°)

[aswin0]

I find it strange that you are unable to increase the distance. Maybe you can explain this. If you look at the shape of the sensor than you see that you already gain 3 cm in respect to the shape of a US sensor.

The beam of the sharp sensor actually is very narrow. It has to be, as its working is based on triangulation. The right side of the sensor projects a IR light spot on the object and thevleft side measures the angle at which the light spot is seen. From the angle and the distance between the led and the receiver the sensor calculates the distance. This will only work if the light spot is small. Hence it's beam is very narrow.

Another suggestion. Why don't yo make a probe using a touch sensor and a motor. You move the probe using the motor. When the touch sensor is pressed you calculate the distance from the motors Tacho.

[HaWe]

I find it strange that you are unable to increase the distance

aswin, actually I'm curious why you're asking this, do you suppose me to be not sure about my own requirements?
I actually don't find it strange, it is as it is because I have to place the sensors (actually 3 of them) halfway inside and outside the middle of the claw of my chess robot to center the pieces exactly before grabbing them.
The accuracy of measuring the center of the pieces must be less than 4mm. That requires a detection angle of about 10° or less at a distance of 1cm, but for 6cm min distance the detection angle has to be less than 2°!!

So do if you don't know a sensor which has a min range of 1cm with a detection angle of less than 10°, could you probably suggest a sensor which has a min detection range of 6cm with a detection angle of less than 2° instead?