GP2D12 vs GP2D120 for Obstacle Avoidance

[Parth]

Hey everybody! I'm mapping out to build an obstacle avoiding robot and I have a small problem. For my 'eyes', should I use the Sharp GP2D12 or the Sharp GP2D120 to avoid obstacles.

In my opinion, the GP2D12 can see objects further, so it seems like the obvious choice. However, it obscures obstacles that are close. But, why wait to turn when you could see the object before? You know what I mean?

Does anybody have any opinions on which sensor I should use? (PS: I am only willing to pay up to $20 for any sensor; I'm on a strict budget!) Thanks!

[Webbot]

But, why wait to turn when you could see the object before?

Thats fine if you are going in a straight line. What happens if you see something 50cm away and start to turn and, ' bang', you;ve just turned into something that is NOW directly ahead of you?

In my opinion all robots need to deal with the 'up close and personal stuff' first - be it via short range IR or even microswitches - and then push out the envelope so that these will be required less. But they WILL still be required.

[Parth]

Oh, I see. With the GP2D12 it could hit something while it's turning. I get it now. So, it seems like the GP2D120 (although having to be closer) would be best for the kind of robot I'm planning to build. Thanks for the help!

PS: I would use the GP2D12 with microswitches, but I'm not a big fan of microswitches...

[pomprocker]

I have done this already with the $50 robot. i have the gp2d12. just follow the sharp IR upgrade on the robot. mount the servo far back enough on your robot to cancel out the close distance it can't see. the servo will constantly scan left and right. then you just need code to do object avoidance. its really simple 3 or 4 lines of code. let me know if u need help with the code.

[Parth]

OK, thanks for the help!

[Admin]

Why not get both sensors? One for really close up, and one for really far away.

[ceruleanplains]

from experience with scanners... it's a good idea to try and calibrate your drive servos for your forward/back/left and right subroutines well (or use an encoder to help).  Otherwise you get nasty drift to the left or right that over a distance of about 2' can move a few inches.  This can result in you banging into the the walls if you aren't scanning all the time (which eats up battery and also introduces the 'faith' factor)... 

All being said and with your budget.. I'd recommend adding something on the side to help you keep a fixed distance from the wall also. You could make a half descent system yourself with an IR LED / IR receiver pair for about $3.