go_away

Author Topic: Which optical sensor should I use?  (Read 513 times)

0 Members and 1 Guest are viewing this topic.

Offline HabTopic starter

  • Beginner
  • *
  • Posts: 2
  • Helpful? 0
Which optical sensor should I use?
« on: May 30, 2011, 05:32:14 PM »
Hi,
I'm trying to design a circuit (with a controller) that would allow me to take the input from two or three optical sensors (I don't know which type fits best) and compare them, then it would give me a simple binary output (left or right) based on the comparison.
The sensors would be looking at a well illuminated surface from an angle (say they are mounted on the front of a robot, no more than 12 inches off the ground), and I want to detect a difference in illumination, indicating an object (or a shadow) on the floor. Comparing the input from two (or three) sensors installed side by side and aimed properly so the fields of "vision" don't overlap much, should allow me to tell if the object is to the left or the right.
Notice that the "objects" may not be three dimensional (they could be just flat on the floor, or maybe even "painted"), so I believe that would exclude the possibility of using sonar. That's why I'm inclined to look into color or light detectors, since I'm more interested in "seeing" anything darker than the surroundings.
Also I need to "see" as far a three to six feet in front of the bot...
Which sensors should I go for?
Any help is really appreciated.
Thanks.

Offline Soeren

  • Supreme Robot
  • *****
  • Posts: 4,672
  • Helpful? 227
  • Mind Reading: 0.0
Re: Which optical sensor should I use?
« Reply #1 on: May 31, 2011, 04:06:11 AM »
Hi,

I'm trying to design a circuit (with a controller) that would allow me to [...]
Is this just a very odd way of saying that you need to make a line detector?


The sensors would be looking at a well illuminated surface from an angle (say they are mounted on the front of a robot, no more than 12 inches off the ground),
That may be a slight problem with conventional sensors.
How long is your experience in electronics and programming?


Also I need to "see" as far a three to six feet in front of the bot...
Ouch. That leaves you around two choices:  LASER scanner or camera.


Which sensors should I go for?
That depends on your experience, but do take a look at the CMU cam.
And before that... Consider if the sensor could be placed closer to ground and be reading closer to the vehicle.
Regards,
Søren

A rather fast and fairly heavy robot with quite large wheels needs what? A lot of power?
Please remember...
Engineering is based on numbers - not adjectives

Offline HabTopic starter

  • Beginner
  • *
  • Posts: 2
  • Helpful? 0
Re: Which optical sensor should I use?
« Reply #2 on: June 01, 2011, 10:25:08 AM »
Hi Soeren.
Thanks for replying...

Is this just a very odd way of saying that you need to make a line detector?

No is not... I need to literally find spots or mostly flat objects on the floor, with the characteristic of them being darker than the surroundings.

That may be a slight problem with conventional sensors.
How long is your experience in electronics and programming?

I've worked with electronics in the past, both analog and digital. But I have never done robotics "per se".
As far as programming, I have some experience with BASIC, C++ and scripting. I also did a lot of low level programming back in the days (Zilog's Z80)

Ouch. That leaves you around two choices:  LASER scanner or camera.

I was afraid that would be the direction to take... and when I say "afraid" I mean it in the sense that this would rule out cheaper sensors, which makes the whole thing pricier to manufacture and sale.

That depends on your experience, but do take a look at the CMU cam.
And before that... Consider if the sensor could be placed closer to ground and be reading closer to the vehicle.

I took a peek yesterday at the CMUCam, and it looks promising...
Making the sensing area smaller would mean that the robot will be very shortsighted, which makes it harder for it to cover a large area finding objects in a "smart" way (other than going around randomly and finding whatever comes really close to it).

Thanks again for your reply... and any other advice would be really appreciated.
Regards.

 


Get Your Ad Here