Society of Robots - Robot Forum

Electronics => Electronics => Topic started by: neo01124 on October 11, 2007, 08:35:55 AM

Title: Line follower sensor dilemna!!
Post by: neo01124 on October 11, 2007, 08:35:55 AM

Hi y'all!! This is my second post
Well i finally got down to building a line follower and worked on it for two weeks non stop. Made a pretty neat analog logic unit(using gates, k maps etal) and in the initial stages(breadboard) the sensor arrangement(LED+LDR) had given a good resolution between white and black but on the day we assembled everything onto the body whoosh no resolution!!
Then we moved onto ir led+reciever arrangement and made it exactly according to data at
http://www.roboticsindia.com/modules.php?name=News&file=article&sid=71 (http://www.roboticsindia.com/modules.php?name=News&file=article&sid=71)
but it also didnt work for some strange reason then in a last ditch attempt we resorted to reflective modules(on2509) but they seemed to work only at a particular distance from the surface and such an arrangement isnt possible on our chassis.And so my line follower is stalled for the moment!!
Guys i need some serious help quickly with regards to this.Thanks in advance!!
 

Title: Re: Line follower sensor dilemna!!
Post by: Admin on October 11, 2007, 06:39:28 PM

Yea, all the reflective sensors are dependent on the distance. Its entirely unavoidable. You will need to lower your sensors closer to the ground.

This is what the datasheet of a reflective sensor would look like:
(http://www.societyofrobots.com/images/sensors_color_distance.gif)

(output vs distance)

Title: Re: Line follower sensor dilemna!!
Post by: neo01124 on October 11, 2007, 10:56:08 PM

But what about the IR rx tx arrangement, i dont get where i am goin wrong with that i used those exact values and it doesnt give me any resolution between black and white!!

Title: Re: Line follower sensor dilemna!!
Post by: creedcradle on October 12, 2007, 03:38:49 AM

Quote from: neo01124 on October 11, 2007, 10:56:08 PM

But what about the IR rx tx arrangement, i dont get where i am goin wrong with that i used those exact values and it doesnt give me any resolution between black and white!!

LED+LDR << LED+PHOTOTRANSISTOR

the sensisitivity of LDR is less sensitive, i recommend you to use a phototransistor

have these as your reference
http://e-gizmo.com/ARTICLES/VBW77/VBPW77.HTM
http://www.kmitl.ac.th/~kswichit%20/LFrobot/LFrobot.htm


but the link you posted above is a very good amplifier, two years ago, i constructed the same circuit with my mobot and it was working fine. LM324 comparator is pretty good.

Title: Re: Line follower sensor dilemna!!
Post by: Admin on October 12, 2007, 04:39:09 AM

I perfer using a photoresistor just because it makes debugging easier . . .
http://www.societyofrobots.com/robot_mobot_2007.shtml