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Author Topic: sensor for obstacle detection  (Read 4237 times)

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Offline junior000Topic starter

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sensor for obstacle detection
« on: January 26, 2008, 01:32:06 PM »
for the obstacle detection which is better

1.sharp ir

2.ultrasonic

3.laser

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Offline SmAsH

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Re: sensor for obstacle detection
« Reply #1 on: January 26, 2008, 02:51:48 PM »
i would say ultrasonic but its pricey...i usially use sharp ir its cheap and effective.


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Offline BANE

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Re: sensor for obstacle detection
« Reply #2 on: January 26, 2008, 04:36:08 PM »
It entirely depends on what type of application its for (meaning range).

PING))) ultrasonic (6" to about 196" acturatly)

Laser (never used one for range, but I believe there simular to an IR)

Sharp IR (recommended for mid range but $15 to $20, you can make your own for alot less if your only measuring short distances)

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Offline airman00

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Re: sensor for obstacle detection
« Reply #3 on: January 26, 2008, 07:54:30 PM »
what kind of obstacles are we talking about?

Sonar is the most accurate , Sharp IR is middle accurate , and homemade IR ( for me ) is least accurate of the three, but still accurate enough for threshold obstacled avoiding

LASER is probably the best , but I have used it once with a webcam , but messed up somewhere in the code , so ill fix it some other time

My personal favorite ranging sensor : Parallax PING Ultrasonic Sensor
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Offline SmAsH

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Re: sensor for obstacle detection
« Reply #4 on: January 26, 2008, 08:00:04 PM »
something airman00 forgot to add: what range are we talking about because some are built for 3m+ and some less than 30cm...

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Offline junior000Topic starter

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Re: sensor for obstacle detection
« Reply #5 on: January 26, 2008, 11:03:57 PM »
the range is less than 30 cm....
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Offline SmAsH

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Re: sensor for obstacle detection
« Reply #6 on: January 26, 2008, 11:17:13 PM »
oh ok. laser if you know ur stuff pretty well. then i'd say sharp ir.


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Offline airman00

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Re: sensor for obstacle detection
« Reply #7 on: January 26, 2008, 11:29:28 PM »
the range is less than 30 cm....

any of the three sensors are good choice

there are different types of each sensor
for example some IR sensors have a range of 12" but cannot see less than 3" , while others can only see below 3"

I like to use ultrasonic , but I've used the Sharp IR sensor family quite a bit before I came upon the PING sensor.

A Sharp IR sensor is what you want I guess.......
post the specific sensor part number and we'll tell you if its good
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Offline junior000Topic starter

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Re: sensor for obstacle detection
« Reply #8 on: January 26, 2008, 11:35:56 PM »
post the specific sensor part number and we'll tell you if its good

we have come with is471f sharp ir sensor.have to build a circuit for it though
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Offline airman00

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Re: sensor for obstacle detection
« Reply #9 on: January 26, 2008, 11:59:27 PM »


we have come with is471f sharp ir sensor.have to build a circuit for it though


OK so build the circuit and tell us when you are done

BUT you should know that all that sensor is doing is giving you a digital binary output - if there is an obstacle closer than 3 inches or not

you wont be able to tell how far away an object is , only be able to tell if its within 3 incehs of you

This sensor ( http://www.acroname.com/robotics/parts/R146-GP2D120.html ) is a rangefinder ,meaning it will give you the distance to the object and not just a digital ouput of " Its within 3 inches of the robot"


Now the question is , do you need ranging or just digital binary output
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Offline lego-robot

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Re: sensor for obstacle detection
« Reply #10 on: January 27, 2008, 12:54:20 AM »
sorry just to ask. is binary output quite easy to setup? im a beginner and think it would be. but i barley know anything about robots.

Offline airman00

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Re: sensor for obstacle detection
« Reply #11 on: January 27, 2008, 07:11:39 AM »
Binary output uses a comparator - so if the sensor gives a reading above this voltage , then you get a signal of 1. If a sensor gives a reading less than that voltag e, you get a signal of 0.

Since the range of an object from the sensor changes with voltage output of the sensor , the signal of 1 will only happen when a certain voltage is reached , when the sensor detects an obstacle within 3 inches .


Search google and wikipedia for how to use a comparator
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Offline junior000Topic starter

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Re: sensor for obstacle detection
« Reply #12 on: January 27, 2008, 11:17:16 AM »
we are using sharp ir is471f for obstacle detction.

and for line detection we are using til 81 and til 31.til 81 is the receiver and til 31 transmitter.we have built the circuit and for white colored object the range is around 15cm.The output is either 2v or 0v.Its working like a comparator.
quite happy with the way its working.
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Offline bietz

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Re: sensor for obstacle detection
« Reply #13 on: January 27, 2008, 01:08:20 PM »
Sonar is the most accurate , Sharp IR is middle accurate

No, the Sharp IR is more precise than any hobby sonar. The sonar is a lot noisier the IR in general.
*But although an IR sensor such as the Sharp ones only returns the specific point in front of it (so that it might find a point you don't want), a sonar takes a sort of average.
*Also, an IR sensor won't detect very dark surfaces because the light is absorbed, whereas ultrasonic waves are always reflected.
*With the Sharp IR, you also have the problem of non-linear output, whereas a sonar gives you the exact time it takes the wave to go and come back to the sensor (from there you can easily find the distance).
*The Sharp IR is easy to read from a microcontroller, but you need an ADC. The PING))) from parallax is actually pretty easy to use as well, and doesn't need an ADC

Offline airman00

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Check out the Roboduino, Arduino-compatible board!


Link: http://curiousinventor.com/kits/roboduino

www.Narobo.com

 


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