Which Ultrasonic Sensors for positioning

[mrjagdad]

Something we want to try out.
We want to make sure we use the proper sensors

The idea is to have a sensor on either side of the robot the width
of a crate. The robot can move back and forth, left and right.
The idea is:
1) Move the robot within a few inches of the crate.
2) The operator clicks a button the the robot moves to
the left or right to center it on the crate.
3) The sensors will mark when both are not directly in front of the crate,
i.e. they are in either side of the crate.

We need a sensor with a thin beam.
I have looked at the two Andy Mark has available MB1200 and MB1013

Does anyone have experience with either, or a better one.
Again the beam needs to be thin to mark when the sensor is no
longer in front of the crate.

Thanks to all.
MrJagDad
Mentor Team 4361

[Alan Anderson]

Ultrasonic sensors are good when you want to know how far away something is. For simple presense/absence detection, expecially at very close range, I would suggest an optical sensor like the Banner QS-18 series.

[otherguy]

If you do find that knowing distance from the tote would be useful (like if you wanted to make sure the robot was square to the tote), I'd suggest trying out IR ranging sensors.

TherTheres a good overview of the Sharp sensors here:
Http://www.acroname.com/articles/shape.HTML

We've found uses for them on all our robots since 2012, and will likely be using them again this year.

You could buy a few with the digikey PDV that came in the KOP. They are also sold at many online retailers.
Http://Pololu.com
Http://SparkFun.com
Http://Adafruit.com
Http://Octopart.com

Make sure you get 3pin JST cables with them, otherwise you'll be soldering wires to these...

Some things to note. Some of the plastic housings on these sensors are conductive, so make sure they are isolated from the chassis.
Also. The voltage drops as objects get closer than the minimum specified range, this could lead to problems with your code reporting incorrect distances. Either mount them far enough in to your chassis so you can't get invalid values, or handle the condition gracefully in your code.