Effectiveness of LM35 for an industrial application

[ADGAN]

Hi! I'm designing a system which control some relays for a saw mill. Additionally I'm planning to use LM35 as a temp. sensor to detect a fire. But how effective it would be? The saw mill is an open and large area.

 

[udayan92]

In addition to heat, a fire also gives off a large amount of smoke. In addition to LM35 temperature sensor, interface a smoke sensor as well. That way the system will be more effective in detecting a fire.

 

[jiripolivka]

Fire detection should operate fast, therefore PIR detectors and smoke detect combined may be best. Recently, Fluke and other companies offer IR cameras which can directly indicate a fire source in a scene. Some video processing is required but there are commercial systems capable to identify a person or even a face, so they can be programmed to output a fire alarm, fast and efficient, for a modest cost. Such IR cameras can even indicate increasing local temperature before a fire starts.

 

[ADGAN]

Thank you for the replies. I'm using a PIR sensor for this project. But how can I detect the fire from the PIR sensor?

 

[chuckey]

I do not believe that this is the correct sensor to use. The reason for this is the very small effective sensing area and the long time it takes to register a temperature.
A saw mill is a very difficult area to detect fires in because of the random amount of dust, any sensor might get covered in dust which it could detect as a fire. There is also the problems associated with any built in extraction systems in that they will automatically "extract" smoke as well as dust, so a fire some where could have its smoke extracted along with the dust from cutting, leaving a relatively clear atmosphere until the fire gets very big.
I have seen mmany sorts of systems and I would go for "firewire". This is a special cable made from two cores of copper plated steel wire, each conductor insulated with a low temperature rated insulation. The two cables are then covered with a red sleeve and a permanent twist put in the cable. The stuff we used was rated to go short circuit between the cores at 70 degrees C. So to use this cable you just string it around and take one end of the conductors to your fire detection circuit. The other ends should go to a "test" switch to simulate a fire. The stuff is very awkward to work with as it does not like being bent around corners as you put extra tension on it and it might go short circuit at any time!. Also to save on the expensive Firewire, you can use it in sections with ordinary wire in between. Such as :- https://www.patol.co.uk/products-services
Frank

 

[ADGAN]

Thank you. I too agree. I thought of dropping the idea to make the fire detection system.