Author Topic: IR Rangefinder  (Read 5001 times)

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Offline megaman935Topic starter

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IR Rangefinder
« on: June 22, 2007, 08:24:21 AM »
http://www.acroname.com/robotics/parts/R146-GP2D120.html
Is this a good IR rangefinder?
And if so where do I (and where) connect it to the microcontroller?
Right now I'm in the planning stage of my first robot and I'm hoping to make a sumo bot (not quite stampy but pretty close) and I'm wanting to find an IR Rangefinder that can do what his can. I don't think I'll be competing, but I'd like to make one if a competition comes my way. Thank you,

Mega
« Last Edit: June 22, 2007, 06:11:20 PM by megaman935 »

Offline megaman935Topic starter

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Re: IR Rangefinder
« Reply #1 on: June 24, 2007, 02:26:36 PM »
A quick question- if I have it go after things like stampy will it go after things that don't move? cause the only thing I'd want it to go after is me, my brother, or my cat. :P

Offline frank26080115

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Re: IR Rangefinder
« Reply #2 on: June 24, 2007, 06:05:56 PM »
Yes (I think it's the exact same one Stampy uses)
Plug the output into an analog to digital converter pin of your microcontroller, if your microcontroller has an analog to digital module, connect the other two to the ground and Vdd

Tracking motion is all in the programming, you will need to compare two results and if there is a significant difference, it indicates movement, this will require the robot to stay still for two complete range scans, compare, then move
There might be another way (doppler effect with IR? ultrasound?)

Maybe you can program it to predict where the object is relative the the robot after each move, then you can have the robot move constantly while looking for moving objects.

Offline megaman935Topic starter

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Re: IR Rangefinder
« Reply #3 on: June 25, 2007, 06:45:54 PM »
Ok, so I'm gonna use this microcontroller:
http://www.sparkfun.com/commerce/product_info.php?products_id=666#
do I need a programmer/program to program it?
-sry, noob question... :P
Oh, and would anyone reccomend a camera instead?
« Last Edit: June 25, 2007, 06:49:38 PM by megaman935 »

Offline frank26080115

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Re: IR Rangefinder
« Reply #4 on: June 25, 2007, 09:58:43 PM »
An Arduino uses a bootloader, the FTDI chip on the board allows USB signals to be translated into UART signals, which is loaded into the microcontroller and that is how it's programmed

No, you don't need a programmer

A camera won't make motion sensing any simpler
Here's an idea... Get http://www.parallax.com/detail.asp?product_id=555-28027 , you still need to stop your robot once in a while to actually sense motion

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Re: IR Rangefinder
« Reply #5 on: June 27, 2007, 07:01:59 AM »
The range on that sensor is only 1 foot. Look at the others to choose the range you want.

The one I used is this:
http://www.acroname.com/robotics/parts/R48-IR12.html

Quote
if I have it go after things like stampy will it go after things that don't move?

It goes for the first thing it see's in a preprogrammed range area, doesnt matter if it moves or not. It uses the edge to determine a chase heading. To get it to identify objects requires more advanced 2D mapping (do a scan, store data in an array, then run an algorithm to identify target).

Quote
Oh, and would anyone reccomend a camera instead?

On my newest robot Im going to combine a CMUcam/AVRcam camera (target ID and X, Y location) with sharp IR (distance away) to identify a target. For a low budget hobbyist its probably the best way to do it.

Offline megaman935Topic starter

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Re: IR Rangefinder
« Reply #6 on: June 27, 2007, 07:28:23 AM »
Yeah I was looking at your robot. looks like a good way to start for anyone who wants to get into robotics. the arm is a good first step to a more advanced robot arm and the body does have room for little "tweaks".
I don't have cad so I'm going to have to explain this through words only. My robot is going to have a "hand" like the one on your robot, only it can open/close it because of the two servos. the hand is split in two so a servo can turn one then the other moves the other. I'm going to have a small thin board that is an "L" shape so that I can connect another servo to turn the whole "hand" 90 degrees. sound logical?

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Re: IR Rangefinder
« Reply #7 on: June 27, 2007, 07:34:30 AM »
Quote
I don't have cad

yes you do :P
http://sketchup.google.com/

Quote
the hand is split in two so a servo can turn one then the other moves the other. I'm going to have a small thin board that is an "L" shape so that I can connect another servo to turn the whole "hand" 90 degrees. sound logical?

There are a billion ways to do it . . . just make sure you make your gripper ultra light. You will have problems otherwise. Ill add a gripper to mine after I get all the fundamentals worked out. Ill probably have a wrist joint and a clamping joint, both with miniature servos.

Offline megaman935Topic starter

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Re: IR Rangefinder
« Reply #8 on: June 27, 2007, 07:39:51 AM »
miniature servos.
where do you get those? Otherwise I'm using hs-311s and that wouldn't look very good. I'll try to scan my drawings and show em to ya.

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Offline megaman935Topic starter

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Re: IR Rangefinder
« Reply #10 on: June 27, 2007, 07:54:41 AM »

I've named it Sam.
« Last Edit: June 27, 2007, 07:55:19 AM by megaman935 »

Offline megaman935Topic starter

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Re: IR Rangefinder
« Reply #11 on: June 27, 2007, 08:08:44 AM »
Of course, this is only a quick drawing that I did in my sleep. ::)

Offline Robotboy86

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Re: IR Rangefinder
« Reply #12 on: June 27, 2007, 01:45:15 PM »
The sharp's are great stuff, be aware of its short comings though.  Depending on which range you get(Short range of long range) they are NOT accurate for the first few cm's.  They will give you readings that are very far off, also it uses a non-linear return.  So lets say it gives you a return of 55(out of 255), and that means 11 cm.. 65 might only mean 13cm, while 95 cm could mean 24 cm.  They go in order, but they are not spaced out evenly. Just google the model and you will find a ton of methods for graphing it out.

good luck :)

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Re: IR Rangefinder
« Reply #13 on: June 27, 2007, 01:59:40 PM »
Robotboy86, the term you trying to say is 'non-linear sensor' ;D

megaman935, since my newest robot needs accurate distance data and Ill be using that particular sensor, I should have code to linearize it written up in a week or two. Let me know when you need it and Ill post it.

But you probably wont need linear data if all you are doing is edge detection . . .

Offline megaman935Topic starter

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Re: IR Rangefinder
« Reply #14 on: June 27, 2007, 03:25:01 PM »
Robotboy86, the term you trying to say is 'non-linear sensor' ;D

megaman935, since my newest robot needs accurate distance data and Ill be using that particular sensor, I should have code to linearize it written up in a week or two. Let me know when you need it and Ill post it.

But you probably wont need linear data if all you are doing is edge detection . . .
Well, I started this post before I really thought about it. How do you make codes? I'm going to use an arduino microcontroller. I'm planning on making it an r/c robot- my friend is going to make a 50$ robot and I'm going to hopefully thrash him in a little duel. Would it be easier to have it do it on itself? :P
My robot's arm will require 3 servos (2 that need to go at the same time) I'm probably going to use dc motors for the wheels (though not completely certain)
should I get a 6 channel transmitter package?
« Last Edit: June 28, 2007, 10:41:23 AM by megaman935 »

Offline megaman935Topic starter

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Re: IR Rangefinder
« Reply #15 on: June 27, 2007, 04:54:02 PM »
Oh, and I can't find the size of the Arduino USB Board... If someone could supply me with that information, I'd be much obliged. :P

Offline megaman935Topic starter

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Re: IR Rangefinder
« Reply #16 on: June 28, 2007, 10:29:23 AM »
Nvm- I emailed the staff at sparkfun.
The measurements are as follows:
Length: 2.7"
Width: 2.1"
Height: 0.5"
This is the Arduino Usb Board.

Offline iNFINITE

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Re: IR Rangefinder
« Reply #17 on: June 29, 2007, 11:57:21 PM »
How quickly does this Sharp IR rangers sample data?
I mean the sampling rate of this sharp rangefinders.



Offline Soeren

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Re: IR Rangefinder
« Reply #18 on: July 01, 2007, 06:03:05 PM »
Hi,

[...] since my newest robot needs accurate distance data and Ill be using that particular sensor, I should have code to linearize it written up in a week or two. Let me know when you need it and Ill post it.
I hope that you're aware, that it will only be useable with targets of approx. the same size and reflectivity, as this matters a great deal.

You might wanna scope it out with different targets before you spend a week (or whatever) of proggin'.

For less than mm accuracy, the code for linearizing can be done in a single line or two, but if speed matters, I'd go for a translation table.
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 megaman935Topic starter

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Re: IR Rangefinder
« Reply #19 on: July 01, 2007, 06:06:29 PM »
If I use this:
http://www.parallax.com/detail.asp?product_id=555-28027
what can keep it from hitting things in its path and yet still hit the target?

Offline Soeren

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Re: IR Rangefinder
« Reply #20 on: July 01, 2007, 06:26:29 PM »
Hi,

A PIR sensor will only "see" heated (or cooled) bodies (whether human, animal or anything else) that is moving across more than one of its "zones", so it won't keep your creation from hitting obstacles, as they would most likely be still and at, or close to, the ambient temperature.

As it stands, it won't be able to "see" you walking in front of you, unless you're seriously waisted, zig-zagging your route.

That said, if you want to detect a static body you could allways move the sensor - as long as the body is crossing the zones seen from the PIR's perspective and it's temperature differs from the backgrounds (otherwise it would be invisible to PIR detection).
« Last Edit: July 01, 2007, 06:28:03 PM by Soeren »
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

 


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