I want to make a fire fighting robot
Which sensor can sense fire?
UVTRON flame sensor
I have used the UVTRON flame sensor in a fire fighting robot and it works very well. Unlike other sensors, it is not as susceptible to false triggering from other sources, and I have even seen it detect a candle while outside over 10’ away.
You get one ‘pulse’ for each time a ‘flame type event’ is detected, and you can get some random pulses, but just count how many pulses you get over a period of time and if you see 5 (or more) in on second, it is a flame.
It is great for detecting there is a flame in the room, but is not so great at detecting where the flame is. As soon as my robot entered the room with the candle, it would immediately detect it from the entrance and if not found, I could exit the room quickly. If the flame is there, then you need something else to determine exactly where.
For that, I just used 3x IR detectors - one mounted down low (pointing at the base of the candle) and 2x up higher. The robot would then spin around until the average of the two high detectors - the low detector was above a threshold. By using the lower detector as an ambient light level, it eliminated issues with bright lights/shadows/etc. By using two sensors at the top, you get directional control of which way is the brightest (steer toward the light).
I mounted all 3x of the IR detectors in a narrow cardboard tube about 1.5" long (I actually used spent Estes rocket motor casings) so they were only looking straight ahead.
Another option, if you are using a camera, is to use a camera without the IR filter - like the noir camera for the Raspberry Pi, but this will require a bit more computing power and more processing.
If you are wealthy, SparkFun
If you are wealthy, SparkFun has a FLiR IR camera module.
Sensing flames
I use a uvtron as the absolute definitative sensor, 8 fixed position IR detectors to give general direction (left,right,front) and a TPA81 on a pan an tilt to track the flame as the robot approaches and estimate distance.
George