So why is everyone using IR remote forehead or in-ear sensors... instead of breath? Seems to me that problem has been solved many times over.

And my temperature is always around 35.8degC whether forehead or in-ear...

 

So why is everyone using IR remote forehead or in-ear sensors...?

Because this is a school project that doesn't need to be practical.

 

Wouldn't surprise me... if so, OP needs to go away and do some research on measuring methods and technologies...

 

No it will be contactless. As the human released breath is pretty equal to the body temperature so I decided to make a heat sensor.

Measuring forehead temperature IS contactless with the new IR thermometers.

UPDATE: Missed that this was a school project.

 

UPDATE: Missed that this was a school project.

My assumption based on the symptoms. Not yet realized by others.

 

It will be project for Covid-19. If Human released breath temperature cross 37° that mean he/she has fever. And exactly at that moment the sensor will sense and will glow led to notify danger alert

The notion that the internal body temperature of every human is normally exactly 37°C and that they have a fever if it is even slightly above that is your first and possibly biggest mistake.

Then, even assuming it is, the notion that the temperature of someones exhaled breath exactly matches their internal body temperature is another huge, unjustified, assumption.

Then trying to measure anything at exactly some moment in time is a physical impossibility.

So you probably need to serious rethink your entire approach.

 

Measuring temperature, any temperature, begins with a choice of sensor. You want a non contact sensor so look for one. Non Contact Temperature Sensor and your Google likely works as well as mine does. You may want to look at the MLX90614 IR Temperature Sensor or similar.

You also, as mentioned, can't simply place a cutoff temperature of 37C in there. Temperatures vary by individual.

You can likely buy a handheld IR temperature scanner cheaper than you can build one. But if you want to build one start with a sensor and work from there.

Ron