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ROBOTMAN
06-24-2009, 04:39 PM
I was wondering what sensor I should use to detect a person standing in front of my robot. I need to robot to stop when a person step in front of it. I was thinking of using a camera but it seemed to complex to do using robo realm or python. Also I thought I could also use a infrared heat sensor but I'm not sure how well that word work. Any suggestions would be helpful.

ooops
06-24-2009, 05:00 PM
Range sensors will tell you something is there: http://www.trossenrobotics.com/store/c/2669-Distance-Range-Sensors.aspx out to a reasonable distance but not so much "what" is there.
You can get the security style motion/heat sensors reasonably cheap and hack them, heck I think I even saw a light switch at Home Depot to turn the lights on and off in the room so that they are only on when it is occupied ... that seems a very easy hack, but I didn't look at any of the details.

Adrenalynn
06-24-2009, 05:08 PM
No single sensor is trustworthy for anything.

Do you really need to detect "human" versus "something is there"? Because that's a _very_ complex topic. There's aren't any human detectors out there, just varyingly useful approximations.

ooops
06-24-2009, 05:13 PM
Here is the pdf link for the "light switch" http://assets.twacomm.com/assets/pdf/17875.pdf
Of course it is 120v AC out of the box and you probably don't want to use an extension cord. So maybe it is a bigger "hack job" than expected. The security type motion and heat detectors do a fair job but will your human be moving?

Adrenalynn
06-24-2009, 06:57 PM
Not to mention they also do a fine job of detecting bats, rats, cats, and elephinos.

ROBOTMAN
06-24-2009, 08:30 PM
I need to specifically detect a human but the environment in witch it will be working won't have elephants or bats.:) A distance sensor won't work because I wouldn't want to accidentally serve a wall a drink. Some sort of thermal sensor sounds like the best bet. Now I just need to know which one. Cameras might work but I'm still a beginner so the task of programming it sounds impossible.:)

[edit]
Oh and the motion light activator won't work I have them in my house and they just detect motion out to 30ft not the shape or body heat.

MikeG
06-24-2009, 11:01 PM
Check out Norris labs.
http://www.norrislabs.com/Projects/FollowMeHex/index.html

Adrenalynn
06-24-2009, 11:46 PM
When I did "Christine" a year and change ago, I tried thermopiles. As long as the environment is VERY controlled, they work ok. Take it outside this time of year and everything it sees becomes a human.

I've been working on a video solution since then - I could probably write something up soon, but it's far from ready for public consumption.

MikeG
06-25-2009, 08:41 AM
Early in my career I had a colorful boss. He gave me a project and I really wanted to do the best job possible. So one day he asked if I was done with the project and I replied yes but I just want to add a few more features. He came back a few days later and asked again if I was finished. I replied, yes it works but I want to make it a bit more robust. On his third query he said, Mike you keep telling me you’re building me a bigger bat but I want to play ball right now. I turned over the project.


Maybe ROBOTMAN can start with thermopiles :)

ROBOTMAN
06-25-2009, 10:40 AM
I think that will work. This robot will be working in a controlled indoor environment. Thanks!

Al1970
06-28-2009, 01:35 AM
Hi Adrenalynn:

Since you have used thermopiles before; would they be able to tell if a person was in a room where the temperature was 78? I have tried an IR thermometer with no luck.

Thanks,
Al

Adrenalynn
06-28-2009, 04:29 AM
Depends how far away from the sensor they were. A few inches? Almost certainly - more than a few feet? Unlikely at best. YMMV.

Al1970
06-29-2009, 12:16 AM
Hi Adrenalynn:

That's what I wanted to know.

Thanks,
Al

altwolf
09-12-2009, 12:53 PM
In a controlled environment you could use RFID cards/ readers. Then the bot would even know who the person was and other useful information.

Adrenalynn
09-12-2009, 01:22 PM
That's only if the person walks up and hands it a card. Not great for following a person certainly. DF'ing works great from a distance, less so the closer you get. Simple trig.

altwolf
09-13-2009, 12:11 PM
That's only if the person walks up and hands it a card. Not great for following a person certainly. DF'ing works great from a distance, less so the closer you get. Simple trig.

What is DF'ing? I haven't really looked into RFID too much, it was just a thought. Is the range to read the card adjustable? I always assumed it was; I have used some cards where you just get into the general area and the system is triggered, and others where you pretty much have to place the card directly in front of the reader.

I wonder if there would be any way to get directionality out of an RFID system, so the reader could figure out where the card actually was in relation to the reader. I can't really think of a way that could happen, but it would be cool. That's a topic for a different thread though.

Adrenalynn
09-13-2009, 02:08 PM
"DF'ing" is short for Radio Direction Finding.

No, the read range is not adjustable - except by changing the size of the antennas and the gain of the transmitter - and that is still entirely dependent upon the environment.

The way to get directionality is by adding more antennas and using an array, and doing doppler direction finding. But you're not going to pick one person out of a crowd. More like one building out of a city. The closer the antennas get to the transmitter, the less accuracy you'll have. That's the simple trigonometry.