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line follower modulated circuit

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andreahmed:
hi, i need your opinion about this circuit , i wanted to modulate the infrared LED emitter and just recieve this frequency and cancells the ambient light , i still didnt test it , but should it work or no ? im in a contest and really dont have time and need ur opinion.
http://i14.tinypic.com/2zhf5tj.jpg


thanks

Admin:
Do you have a microcontroller on board your robot? You can quickly do that circuit in software with significantly less effort/cost.

This post has some relevance:
http://www.societyofrobots.com/robotforum/index.php?topic=361.0

As for the circuit, I really cant be sure unless I sat down and built/tested it myself, as you said  :-\
sorry!

andreahmed:
thanks for replying
ya i do have one but its 89C52 and doesnt have an ADC :S also i cant really change the whole platfrom and the make new circuit for AVR or PIC and buy new software and burner ..etc :S

i wanna ya to see how much the ambient light there in the contest ...
this is a pic from the last year contest ^^ i were there and used LDR and it was  very bad with shielding !

dont know really what to do  :(
http://i11.tinypic.com/3zi1z6d.jpg

Admin:

--- Quote ---its 89C52 and doesnt have an ADC
--- End quote ---
ouch! your doing IR without ADC?!? why?!?!?!  :P

looking at the pic, the ambient light isnt that bad. ive done line following robots that follow a white line on a light grey background outside on a bright cloudless sunny day - and without any modulation. its doable.

the trick is to use more than one LDR, so that when placed on your bot, it is only possible for one of them to be on the white line at a time. if neither are on a white line, they should read about the same. but if one goes on the white line, the voltage will change on just one - a difference that can be detected with a comparator IC (or ADC).

if you are still concerned, there are other basic tricks, like cover your sensor area with garbage bags or other IR absorbing material so less IR light gets in.

andreahmed:
Hi, thanks for reply , i will use a new platform which has an ADC and use the thershold algorithms ,can you suggest a good PIC micro with easy compiler ?? i dont have really time ^^

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