I need to construct a circuit for a robot, so it can follow a red line. I'm thinking of using something like this http://www.instructables.com/id/Color-Detection-Using-RGB-LED/ , but switch out the RGB with a green LED and no microcontroller, only for one light color. I am wondering if this would work. And if I need a comparator?

 

It must be the time of the year for design projects. I've moved this to Homework Help.

 

See here.

You two should get together and tackle this project together!

Since this is homework....what is it you think you need? How are you going to approach the problem?

And if I need a comparator?

Do you need to compare things? That is what a comparator does....

 

I need to detect the lines colour. I am wondering if that mentioned circuit will work. I'm thinking of only using one sensor to exclude the comparator, but what will be the disadvantages of this?

 

I'm thinking of only using one sensor to exclude the comparator, but what will be the disadvantages of this?

Robot following line .........
Suddenly forgets where the line is....robot goes ""!

You might yell out.
"Get back to the road you little bugger".

 

I need to detect the lines colour.[...]

So this line follower is only to follow a specific color? And without a microcontroller? Anything else we should know up front?

 

Yes. Well I can get a microcontroller, I just wanted to do it as simple as possible. The background doesn't matter.

 

So why don't you start first.

Are you asking to give you a diagram ?

 

Ok, making headway. One question, will the above circuit be compatible with 9V battery? And coudl someone help me understand the circuit. I'm having trouble understanding the RED LED. why does it light up (if RGB replaced with blue LED) when blue light comes on. If the circuit has a current shouldn't it be lighted up like the blue LED all the time?

 

If you want to talk about the circuit, post it first.

Not a link to somewhere.
Post the circuit that you want to make.

 

Sorry. here is the circuit.

 

what do you expect it to do?

 

To detect weather or not the colour of the object corresponds, to the colour of the LED.

 

Ok!
Simple fact. To detect a certain spectrum you need to apply filter to the detector which will block all the color except the color you want.

Unless you make a circuit that can detect a certain color. Which includes comparator and other circuits too

 

What kind of filter, and how?

 

IR filters, color filters.
Do a google search and you will see plenty.

The filter needs to be placed in front of the detector. Then the detector will produce a signal when that light is available. The detector can detect a broad spectrum but the filter blocks all but a certain spectrum to fall in the detector.

But for this I think a LDR will suffice as photo detectors detect Infra Red. Which eyes can't see.

May be some other member can highlight this.

 

ok, thanks. But what about the 9V(can it handle that?), and can you give a little information on why the indicator LED lights up, if the correct spectrum is recieved by the photoresistor. What I see is that the current passes trough the photoresistor(which initial resistanc evalue is quite large, meaning no big voltage on the "branches"), but if the light is absorbed the resitance lowers, and light the indicators lights up. What I don't get is why does the RGB(or any single colour LED) lights up before hand. Do i need to apply a separate voltage to it?

 

Well !
Don't you get it. That is the reason for so many circuits and comparators.

You have to make it simple. Then sometimes simple things don't work and that is what you get if you wire a LED in series with a photo resistor.
I believe one or other will end up in smoke sooner or later.

A specific color line following robot cannot be made with just passive components.