Krumlink

I've been working on ASAP (as small as possible) Line following robot, and as the name suggests, It doesnt have to be ASAP. I have been working on modifying the line following robot as designed by Dave cook at www.robotroom.com, and I cannot figure out how to get the circuitry to not just veer off left when it cannot find the line. This is what I mean:

http://www.youtube.com/watch?v=2bVcqKy48F4

It can only go a certain direction when active. Do you have any suggestions as to solve the problem to make it turn rather than chase its tail? I am using a Dual Comparator LM393 and I do have a Quad comparator (LM339) just in case.

Schematic location (it isnt the schematic from the book, but it is the same thing)

http://images.google.com/imgres?imgu...icial%26sa%3DG

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Pommie

I can't help with your problem but as you mentioned ASAP, I thought you might like this.

Mike.

Krumlink

Ive seen that many times, and I love it!

Problem is that it uses a ATMEL. I like PIC.

Cool linky though.

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kjennejohn

Hi, Krumlink.
I'm mystified as to why he uses six photosensors. I have read a few discussion about designs of line following robots. General concensus usually says only two sensors are needed, and more may just add to design problems. A lot of these designs consist of just two sensors, two transistors, batteries and two motors. That is, one motor per wheel. Each sensor drives a transistor which drives a wheel motor. As long as each sensor detects reflected light, both transistors are on, and both wheels are driven. When the robot wanders across (into?) the line (we're talking black line/white floor), the sensor stops conducting. This leads to the transistor "pinching off" or going open circuit, which limits or kills the wheel motor. Thus, the still driven wheel forces the robot to turn towards the now "dead" side. This brings the sensor back over the floor, so it starts to conduct again. This turns the transistor back on, which now drives the wheel motor,and we're running staright again. Or we overshoot, the other sensor now goes dark, its motor dies... If the design doesn't allow for controlled, gradual speed up/down of the wheel motors, the robot ends up lurching along drunkenly, side to side. You can probably account for this with an RC circuit on each transistor's base. When the sensor "goes dark", the RC circuit bleeds off slowly, thus eliminating completely killing the motor and avoiding the "lurch".

There's lots of this on the web, as you already know. This is the minimalist approach. Of course processor controlled contraptions are the only way to go.

Later!
kenjj

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Krumlink

Couldnt I just add a capacitor (10uf or so) across the motor input line? on the drive side not the actual motor lead? Seems like it would still introduce current into the system, making it slowly die off.

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Wingmax

I'm working on one of this too.

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My project: Simple White Line Follower

http://au.youtube.com/watch?v=8Z_MmrdH4oc

http://i271.photobucket.com/albums/j...nefollower.jpg

allbits

It might be because your sensors cannot "sense" the line properly.
1) Disconnect the motors (Electrically)
2) Use a multimeter to compare the inputs voltages of the comparators.
3) Check this for R5,R6,R7 and R8 on the line and off the line.
4) If the results are not good, the photo resistors might have different resistance values. you might have to change it, or "tune" the circuit by adding trimpots.

All the Best!!

Nigel Goodwin

I would disagree, two is the absolute minimum you can use - using more (while technically more complex) gives much better performance (faster, smoother, more reliable).

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blueroomelectronics

I know that gearbox You should add a 0.1uf cap across the motor leads as close to the motor as you can get.

An early Mongoose, showing the 0.1uf caps (yellow) on the motors.

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Smart Kits build Smart People
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Krumlink

Thats not the case. It works just fine, the problem is that it has two states:

On-Off

When it senses a line (left side) it goes right, and on the right side, left. When it loses sight of the line, it just turns in the opposide direction, making me have to make all the paths go clockwise. I am trying to figure out how to make it have 3 states

on-off-on

When it senses a line on one side, it goes the other, but when it loses sight of the line, it goes opposite, making it always stay near the line.

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Wingmax

Thanks Bill.

__________________
May the force be with you.


My project: Simple White Line Follower

http://au.youtube.com/watch?v=8Z_MmrdH4oc

http://i271.photobucket.com/albums/j...nefollower.jpg