Distance Sensors

"Best" depends on a whole number of factors - range, update rate,
accuracy...

Sonar doesn't work too well in noisy environments and may not work too well
at extremely close range..

Deep

You're asking for two things in one package:
- a distance/range sensor
- a communications link

As for distance/range, check out both ultrasound (sonar) and the Sharp
GDP2Dx (e.g. GDP2D12) infrared sensors.
Ultrasound:
- greater distances
- larger sensing "cone"
IR:
- higher refresh rates
- generally cheaper & easier to use
- often less noisy
- suffer less crosstalk between multiple sensors

Both technologies can suffer from unusually absorptive or reflective
materials.

As for communications, many cheap micros will do.  PIC, basic stamp,
MSP430, ARM, Arduino, ...  Here, its generally best to find something
with a supportive community.  RS232 is generally easier to program
than USB, though a few good USB chipsets have come out in the recent
years.


- Daniel

Thanks for your answer.

Perhaps do you know what sonar sensors are installed on the PatrolBot?
They look bigger than the $25-$40 sonar sensors exist on the market.
http://img.linuxexpres.cz/2005/6/roboti/patrolbot.jpg

Those look a lot like the classic Polaroid transducers.

For example, see
http://www.acroname.com/robotics/parts/R13-INST.html

- Daniel

    Questions:
    1.    How big can it be?
    2.    What range do you need?
    3.    How wide a beam width do you want?
    4.    How much can it cost?
    5.    How much accuracy do you really need?

Ultrasonic units are cheap and available, but most of them
have large beam widths and have problems with reflections off
hard surfaces.   Range is centimeters to 10m or so.  Some
have minimum range limits.

Relative reflectance devices are cheap and available, but
usually have very limited range, a few cm.  Useful for grippers
to control grasping.

Angle reflectance devices are available, not as cheap, have
ranges in the 10-20cm range or so, and are reasonably accurate.

Time-of-flight laser rangefinders have accuracy to 1cm, ranges to
tens or hundreds of meters, very narrow beam widths, and tend
to be larger and more expensive than the other options.

            John Nagle