Society of Robots - Robot Forum
Electronics => Electronics => Topic started by: aruna1 on February 20, 2009, 10:10:29 PM
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guys is it possible to use ir reciver circuit with modulation to detect only fire with out getting disturbed by ambient light variations?
thanks
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no one?
:-[
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guys is it possible to use ir reciver circuit with modulation to detect only fire with out getting disturbed by ambient light variations?
No, you have to deal with ambient as well, but you should be able to differentiate.
Make a set up with a candle and experiment.
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well does ambient IR value change rapidly?
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Hi,
Aruna, you really need to get your hands dirty. You have been asking about this subject for quite some time now - 'bout time you get some hands on experience, which will be more giving to you (and fun) than just theory.
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well ya,i made a flame sensor but it is disturbed by ambient light,so I'm trying to build a theory to remove ts effect. if ambient light is constant (or at least doesn't change rapidly) and candle flame changes rapidly then cant we use a capacitor filter to bock ambient light(coz ambient light may work as a dc component)
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Would writing a software to include a fast rise detection algorytyhm solve your problem? rather than filter out ambient IR, it would just wait until there was an immediate rise in the amount of IR detected and act upon it.
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Would writing a software to include a fast rise detection algorytyhm solve your problem? rather than filter out ambient IR, it would just wait until there was an immediate rise in the amount of IR detected and act upon it.
well how to do that?
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Well first of all you need a threshhold value.
If you are using 8 bit readings from your sensor then you are getting a value between 0 and 255.
Ambient light will only fluctuate a certain amount, say a maximum fluctuation of 20 and so we set the threshhold value at 20.
unsigned byte Threshhold= 20 ;
unsigned byte IRreading = [readADC];
unsigned byte IRreading1;
while(1){
IRreading1 = [readADC];
if (IRreading1-IRreading >= Threshhold){
//we must have discovered a fire - do something about it
}
if(IRreading1IRreading <= Threshold){
//the fire must have been extinguished or i cant see it anymore
//stop panicking (unless its behind me.. i'd best have a look ::))
}
IRreading = IRreading1;
}
Something like that really. It doesnt depend on cancelling out the background IR all it does is look for a sudden increase in IR detected. Obviously ambient light can change aswell but not as fast so thats where choosing the correct value for Threshhold comes in.
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THANKS