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Author Topic: sharp ir rangefinder  (Read 3234 times)

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Offline nckspecTopic starter

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sharp ir rangefinder
« on: March 24, 2008, 11:00:39 PM »
I was just wondering. How does your microcontroller know when your sensor is facing forward.

Offline bulkhead

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Re: sharp ir rangefinder
« Reply #1 on: March 25, 2008, 02:48:03 AM »
Why wouldn't your sensor be facing forwards?  If you have it on some panning mechanism, say, controlled by a servo, which is probably the easiest way to do pan it, you would probably set delays in the program after telling the servo to go to a specific angle to ensure that it is at that angle when you take a measurement.  In this case you are making the safe assumption that nothing will physically prevent the panning servo from pointing the IR rangefinder in the direction you want (given a reasonable amount of time).

Offline shimniok

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Re: sharp ir rangefinder
« Reply #2 on: March 25, 2008, 07:09:36 AM »
My firefighting bot Pokey uses a pair of Sharp IR sensors at 90* angles on an array rotated by servo.

The position of the servo is determined by the MCU -- basically pulse width determines orientation.  And servos are rated in terms of miliseconds to cross 60* so you can calculate roughly how many msec to traverse a given angle (about 300-400 to sweep 180* in my case).  So in other words, you can tell it at what angle to point and wait the appropriate time until the servo is done moving.

Hope this helps

Michael
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http://bot-thoughts.com/

Offline nckspecTopic starter

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Re: sharp ir rangefinder
« Reply #3 on: March 25, 2008, 08:36:38 PM »
thank you, thats kinda of what i assumed but i wanted to make sure there wasn't a more competent way
I can't wait to do this project. It will be interesting how my dog will react to a robot following it.

Offline JesseWelling

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Re: sharp ir rangefinder
« Reply #4 on: March 26, 2008, 06:40:27 AM »
You could use an encoder if you wanted less of a timer based solution and more of an Interrupt based solution.

Offline superchiku

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Re: sharp ir rangefinder
« Reply #5 on: March 26, 2008, 06:49:02 AM »
and what do u mean by that???
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Offline Admin

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Re: sharp ir rangefinder
« Reply #6 on: March 30, 2008, 10:51:18 AM »
Quote
and what do u mean by that???

http://www.societyofrobots.com/sensors_encoder.shtml

If your robot isn't doing highly accurate mapping, you can have your robot guess the angle. Thats what I did for my Stampy robot. It knows the angle within ~20 degrees, and that was good enough.

For more accurate mapping, this is what I did on my iRobot Create:
http://www.societyofrobots.com/robot_iRobot_Create_mod.shtml

And another option would be to use a stepper motor
http://www.societyofrobots.com/actuators_steppers.shtml

Offline superchiku

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Re: sharp ir rangefinder
« Reply #7 on: March 31, 2008, 01:18:35 PM »
AND HOW DO U MAKE UR ROBOT GUESS THE ANGLE

IS IT JUST MAKING THE ROBOT GO TO A POSITION HAVING THE BEST PROBABILITY OF FINDING UR OBJECT???
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Offline nckspecTopic starter

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Re: sharp ir rangefinder
« Reply #8 on: April 01, 2008, 01:58:24 AM »
i read through the stampy code and the code has a sensor_angle variable and when is greater or less than some set numbers it determines where to turn. It pretty much keeps a record of how much it turns to guess the angle

Offline superchiku

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Re: sharp ir rangefinder
« Reply #9 on: April 03, 2008, 08:15:39 AM »
sharp ir's can only tell the distance but not the angle i suppose, then how does the robot realise if it has to turn left or right in order to track the object
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Re: sharp ir rangefinder
« Reply #10 on: April 06, 2008, 11:45:33 AM »
superchiku, its in the tutorial:
http://www.societyofrobots.com/robot_sumo.shtml

Offline superchiku

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Re: sharp ir rangefinder
« Reply #11 on: April 06, 2008, 11:49:16 AM »
ya i readt that  :P posted this a long time ago
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Offline Rebelgium

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Re: sharp ir rangefinder
« Reply #12 on: April 07, 2008, 12:09:10 PM »
ya i readt that  :P posted this a long time ago
4 days ago ... ?
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Offline superchiku

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Re: sharp ir rangefinder
« Reply #13 on: April 07, 2008, 12:13:55 PM »
lol long time for me  ;) coz time is valuable  ;D
JAYDEEP ...

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