Discussion in "Project Help" started by    x1alpha    Jul 31, 2008.
Thu Jul 31 2008, 10:28 AM
#1
Hi guys

I'm currently working on an insect robot project...my first robotics project! I'm looking into 2 methods of detecting obstacles i.e. IR and Ultrasound. I cannot seem to choose at this point in time! Can someone give me some guidelines as to which is more reliable and accurate...range is not really a problem.

Thanks.
Thu Jul 31 2008, 01:55 PM
#2
ultrasonics are obviously reliable and accurate as compared to infrared.

there are lot of limitations in infrared sensors like cannot be used in sun coz of ambient light interference etc. where as ultrasonic sensors works on sound waves so no problem in detecting obstacle in any case.
ultrasonic sensor's range is perfect and is very accurate, The only reason for using IR sensors is they are cheap.
So depends on you if you can spend somewhere around $25+ then you can use ultrasonic sensors.
 x1alpha like this.
Thu Jul 31 2008, 02:34 PM
#3
ultra sonic sensors around 30kHz to 40 Khz.. costs u about 600 INR


plus it also depends on what type of obstacle detection u wanna do...


Infrared will need Tx and Rx placed at diferent points .. u can only get the idea of interception at some fixed line angle etc... cause as ajay said they are not reliable.. plus they can come from almost any source....

ultrasonics are based on the RADAR principle.. waves come 2 u after hitting an object or they will simply fade away!

in my veiw u shud look for an appropriate Ultrasonic Tx Rx module around ur local market.



[ Edited Thu Jul 31 2008, 02:37 PM ]
 x1alpha like this.
Wed Aug 06 2008, 10:50 AM
#4
Hey guys

Sorry for the late reply! Been busy some. Thanks Ajay and Shyam...you have cleared up some things for me
Wed Aug 06 2008, 02:29 PM
#5


there are lot of limitations in infrared sensors like cannot be used in sun coz of ambient light interference etc



Sorry to interrupt, but Modulated Ir can be used even in sunlight and the range can be upto 10 meters (with proper driving current).


cause as ajay said they are not reliable



i beg to differ on this statement, a highly reliable obstacle sensor can be made with Ir, the fact that even the most modern entertainment gadgets( TV,Music systems, DVD,LCD TVs etc) use Ir technology for remotes speaks about its reliability.

at first the TV remotes used ultrasonic technology, but later shifted to Infrared also the fact that Light travels faster than sound helped this transition.




Arun




[ Edited Wed Aug 06 2008, 02:47 PM ]
Wed Aug 06 2008, 05:24 PM
#6
I think directivity is the deciding factor between the two...
usonic is more omni whereas ir works more or less at line of sight.

at first the TV remotes used ultrasonic technology, but later shifted to Infrared also the fact that Light travels faster than sound helped this transition.


Angry pets could have further hastened the transition..
 x1alpha like this.
Wed Aug 06 2008, 06:44 PM
#7
well Arun you certainly told me something valuable..

let me create a scenario.

i want a portable device that i can place any where i like..
may be tugged in the upper pocket of my shirt while travelling.. or a pen like device...

now i wud like to detect possible obstacles at some distance say 10 mts..

which technology shud i prefer?


actually x1alpha reminded me of a project done in IIT about the Blind mans stick...
i was thinking of something like that...

so Mr. x1alpha now its tume you shud elaborate your project here
 x1alpha like this.
Thu Aug 07 2008, 02:45 AM
#8


Angry pets could have further hastened the transition..



yes, that might have also fueled the change, the TV viewer had to strike once on aluminum pipe for TV ON and twice for volume up and thrice for OFF all had to be at correct intervals, this was cumbersome and the designers were desperate to find better alternative and settled on Ir.

now i wud like to detect possible obstacles at some distance say 10 mts



Modulated IR can reflect back at 30 feet ( you need to pump pulsed 500ma or more into the IR led)

when it comes to component count, IR uses less components ( 555,Ir Led,Tsop17XX,3 resitors,a cap) but Ultrasonic requires a lot more ICs and discrete components and requires careful alignment.

take a look at the circuit which uses ultrasonic pair and picture of Ir obstacle detector:







Application decides which technique is to be used, and also the entity (robot or a blind human) that needs to be protected adds importance.

since the OP wants a obstacle detector for his Insect robot, Ir can also be used (low parts count,low budget) but when it comes to saving a Blind man's life, surely Ultrasonic method can/should be used.




Arun
 x1alphanischay kumarshyam and 1 other like this.
Thu Aug 07 2008, 06:18 AM
#9
Thank you Arun for your input :-)

OK Shyam, I will explain what I'm doing! Well you know I'm building an insect robot i.e. it will have 6 legs and I'm going to implement a tripod walking sequence where 3 legs will always be on the ground at any given time. I need to give this robot some sort of ability to sense obstacles in it's path and provide a method to make it avoid the obstacle.

I have searched around and found that I would use one of 2 methods i.e. IR or ultrasonic. I scrapped the idea of having a touch sensor because that seems too trivial and the robot would already be right in front of the obstacle making it seem like a blind robot with a walking stick

Anyway, IR and ultrasonic have their own advantages and disadvantages. I'm looking to detect the obstacle at a distance of about 1 meter and gradually implement a turning sequence while it moves forward so that it will eventually avoid the obstacle. I'm looking also to minimize design cost although I have a budget of R700 (Rands...I'm from South Africa :-) ). I have bought a couple IR LED's and receivers and also an ultrasonic transducer pair.

Which of these (IR or ultrasonic) is easier to implement? By the looks of things, it's IR. I want something that will work without being affected by the environment and since a modulated IR wave can do this, then it's one up for IR again.

Thanks all you guy...you have been really great!
Thu Aug 07 2008, 03:49 PM
#10

Thanks Arun sir,

for providing valuable info and helping me to decide between IR or ultrasonic, the cost of U-sonic pair was equal to my total project budget of Rs.600 and Ir sensor could be built for 10% of the project cost (Rs.60). Ir makes more sense to me.

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