Fire Dectection System Circuit

[KYTan]

Hi. I need help in design of a fire detection system. The system is consists of 3 points or 3 houses. There are signals go through those 3 points continuously. When a fire is happen, the sensor in the point will send signal to the system and indicate there a fire. The sensor is replace with switch. Can moore state machine theory and multiplexer can be used in this design? What method is suitable for this design and it is assignment. Thank you and your help will be very appreciated.

 

[Electronics4you]

What is the exact purpose of the system. Do you have some common indicator that one of the sensors has changed state?

 

[magvitron]

if the units are located far from each other, use a zigbee. you can easily program one to read temperature, if you need this with logical ICs, use a three input OR gate. as simple as that!!

 

[KeepItSimpleStupid]

The way simple fire systems work is that each sensor is a switch and the end sensor is terminated with a resistor.

No locaction information is available, but it does indicate trouble if the wire is cut. If you put a LED and resistor across each detector (ceiling) and know the path, you an find out which sensor triggered the alarm.

Sprinker sensors work sort of in the same way. The last zone matters, because all sensors along the path are triggered.

 

[KYTan]

What is the exact purpose of the system. Do you have some common indicator that one of the sensors has changed state?

The purpose is to notify the fire department if a fire is happen.

 

[KYTan]

if the units are located far from each other, use a zigbee. you can easily program one to read temperature, if you need this with logical ICs, use a three input OR gate. as simple as that!!

My design must not use software and use only hardware.

 

[KYTan]

The way simple fire systems work is that each sensor is a switch and the end sensor is terminated with a resistor.

No locaction information is available, but it does indicate trouble if the wire is cut. If you put a LED and resistor across each detector (ceiling) and know the path, you an find out which sensor triggered the alarm.

Sprinker sensors work sort of in the same way. The last zone matters, because all sensors along the path are triggered.

Yup the sensor is the switch. What kind of concept should I use in this fire detection system circuit? Can Op Amp use in it? I thinking of use it as the comparator for the temperature.

 

[KeepItSimpleStupid]

Well, temperature normally isn't fire, but temp sensors exist. Fire sensors normally detect smoke. They are either ionization or photoelectric. Ionization is usually more expensive because of the radioactive source. Photoelectric is simpler, but prone to false alarms. So, why not make a photoelectric detector.

You may actually have to use two different levels of current so your detector circuit can still get some power when activated, although you can "remember" at the panel.

Take a look here for a brief overview: https://ecmweb.com/design/understanding-basic-fire-alarm-systems

 

[JimB]

I assume (hope) that this is just an academic exercise rather than an attempt to design a real fire detection system.

In the real world, fire (flames) are usually detected by a device which senses the presence of UV radiation.
Smoke is sensed by ionisation detectors, (as per the usual domestic type). To detect smoke over a large area a photoelectric detector is often used.

Heat is sensed by the rate of change of temperature.
Often ther are two sensing elements, on which is thermally insulated and so tracks normal (slow) temperature changes along with an uninsulated sensor.
When the temperature changes quickly, the two sensors see different temperatures and the alarm is set.

JimB