Following a line

hvn1

Hi,

What is the preferred component to follow a line: a photoresistor or a photodiode (LED)?

Thanks,,

hvn1

Philip Gamblin

I built a simple tail dragger style· bot that I thought I'd use for line following. It's not real easy. Let me clarify. Program wise and conceptually speaking, line following is relatively straight forward. In my initial line following·foray, I attempted to "roll my own" using some Radio Shack IR transmitter/ reciever LED pairs. One side worked well but the other side was a nightmare.·The repeatability was lousy and·if either the transmitter or reciever is moved the angle of reflection is wacked which means ime for a new "calibration".·As it turns out, both LEDs should be close (less than an inch or so) from the track. I found·I was spending all my time on the mechanical assembly· and stability issues which is neither my desire nor my strength. If you are genuinely interested in line following, I strongly suggest you consider some the Parallax AppMods which are designed for that purpose http://www.parallax.com/detail.asp?product_id=555-27401.

To answer your question, I prefer IR because ambient light is less of an problem

This is simply my twisted experience. The good news is that the test track was fairly simple to ·construct with electrical tape on white poster board.

Philip Gamblin

This looks like a good choice, maybe a pair of these would work. Parallax used to sell something similar, but I didn't find it. This takes care of those pesky mechanical problems. Just bolt it up ( or my favorite hot glue ) and go. http://www.acroname.com/robotics/parts/R185-SINGLE-LINE-IR.html

good luck

Bruce Bates

hvb1 -

Here are the Parallax offerings for line following which I'm told work really quite well, although I've never actaully used them. I mention them in case you don't want to build them from the ground up, and would like to purchase something that's "Parallax-Reliable / Parallax-Supported" and well tested. Sample code is also provided. Two formats are available.

Single QTI Sensor line follower mini-board (neat duaghter-board package!):
http://www.parallax.com/detail.asp?product_id=555-27401

Full line follower parts kit for the Parallax BOE-Bot, but could be easily adapted for other bots: http://www.parallax.com/detail.asp?product_id=28108

Regards,

Bruce Bates

hvn1

Bruce,

I have the standard BoeBot kit. With it are IR LED's...so I suppose I can use those for line following, right?

hvn1