SparkFun Forums

[Pompy]

Hi everyone, new to the site... trying to build a robot capable of detecting hot areas and/or fires... really struggling to decide on a practical and cost effective sensor to use.... wondered if anyone could help with some suggestions.

I am trying to sense heat/flame... such as that of a candle, from say 2 metres.... I want to build an array of cheap sensors, which together with some programming... can resolve the direction of the heat

temperature sensors are obviously no good as they will see a 'wall' of heat as opposed to a flame

thermopile array would be perfect but are way too expensive for this application

infrared sensor would be ideal if I could get one that is triggered by 2um-22um wavelengths (flame) but I can't find them

been looking at photodiodes but im unsure as to how exactly I could fit them to this application

hope someone can help, thanks in advance....

[MichaelN]

The wiki page has some useful info on flame detection:
http://en.wikipedia.org/wiki/Flame_detector

From what I can tell, you are better off using multiple detectors in different wavelengths, to avoid false alarms from incandescent bulbs, sunlight etc.

You are correct that finding sensors is difficult, but you might try photodiodes / phototransistors (which are easily available with a response out to about 1300nm) in combination with a "thermopile" type sensor for mid-longwave IR detection eg:
http://www.melexis.com/prodfiles/000476 ... 47P006.pdf

EDIT: if you're looking for a very directional detector, you'll probably need to add additional optics to each sensor. This is pretty easy for the near-IR photodiodes / phototransistors (you can just use the plastic lenses intended for LED lighting applications), but lenses for the thermopile will be a challenge. You might be better just to use a cheap IR thermometer (which uses a thermopile anyway), since these have a lenses to give a narrow viewing angle.