urgent help:fire sensor-filter ambient IR using modulation

[aruna1]

guys is it possible to use ir reciver circuit with modulation to detect only fire with out getting disturbed by ambient light's IR variations?
this is for my fire fighting robot,i use IR reciever leds to detect fire,but they are disturbed with ambient IR variations
thanks

 

[duffy]

This is an interesting question (though I think there may be easier ways of doing it).

If your ambient sources are coming from lights supplied by mains voltages, a 60 or 50hz "notch" filter might help remove some of the noise.

What sort of detector are you using?

 

[aruna1]

well i use normal infrared sensor photo diode.i want to get rid of Infrared generated by sunlight(mainly,and not from lights)
thanks

 

[duffy]

There's no such thing as a "normal infrared sensor photo diode". They have different wavelengths they are sensitive to, most of the ones used for digital signals are sensitive to much shorter wavelengths than you probably want.

Are you trying to detect the flame itself, or glowing red embers, or what? The flames may flicker a little in a way that's different from sunlight... but it's really going to be difficult trying to do it this way.

I think what you are going to need is a device to look at a larger part of the infrared and visible spectrum. Things that burn will glow brightly at certain wavelengths depending on the chemistry of what's burning. Sunlight has a well defined spectrum that could be subtracted out of the data.

 

[ericgibbs]

hi,
Industrial 'flame' detectors use Ultra Vilolet sensors.

Google for UV flame detectors

 

[aruna1]

well in my country we cant by parts like infrared leds by model number because electronic part sellers recognize all of them as simple IR leds.so there is no way of getting data sheet to find wave length.

I'm trying to detect flame only and get rid of ambient IR. i heard ambient ir will give dc level.so will i be able to block ambient ir using simple capacitor?

 

[duffy]

Sunlight has UV as well as infrared. Industrial detectors use both IR and UV. Not all flame sources are UV rich.

 

[ericgibbs]

I'm trying to detect flame only and get rid of ambient IR. i heard ambient ir will give dc level.so will i be able to block ambient ir using simple capacitor?

As I said Google for UV flame detectors

 

[aruna1]

hi,
Industrial 'flame' detectors use Ultra Vilolet sensors.

Google for UV flame detectors

well I know about that sensor.its too expensive and I dont have enough time to import one.i made flame detector using IR reciver led's now i needto remove ambient IR effect

 

[aruna1]

anyway will capacitor trick i mentioned will work?

 

[duffy]

Probably not, but try it anyway - if you want to pretend everything is "simple". The motion of the robot, clouds, smoke billowing through the window - all these things will make sunlight flicker.

well in my country we cant by parts like infrared leds by model number because electronic part sellers recognize all of them as simple IR leds.

"Simple IR led", huh? Your parts sellers sound like complete idiots.

 

[aruna1]

Probably not, but try it anyway - if you want to pretend everything is "simple". The motion of the robot, clouds, smoke billowing through the window - all these things will make sunlight flicker.



"Simple IR led", huh? Your parts sellers sound like complete idiots.

hmm thats how it is

 

[ericgibbs]

hmm thats how it is

I agree with Duffy, if you use standard IR detectors, the detection of IR from a 'flame' will be unpredictable.