Optical Alarms By: Priya shahiraj

What are Optical Alarms/Basics of how they work

An optical alarm is a fire alarm but it also referred and called to as a photo-electric fire alarm. We have fire alarms in our homes but often do not know hear about optical alarms how they work so here of the basics of how they work before we get more in depth. The first step is that if the fire produces smoke it would enter the optical chamber that is through the vents on the alarm. The second step is that as the smoke enters the optical chambers the smokes particles will cause the infra-red light to be scattered onto the photo diode receptor. The last step is that one the scattered light hits the photodiode light

Parts Of A Optical Alarm

For more of a understanding here are parts of the optical alarms and what they do.

  • The first part the detector it is also the part known as the opening so the smoke can enter
  • The second part is the detection chamber,it has an invisible infrared light beam it is also known as the LED ( light emitting diode)
  • The third part is a photocell which is an electric light detector that works to generate electricity as long the light continues to fall onto it
  • When there is no smoke the light beam is non stop shooting between the led and detector
  • The fourth part is the electric circuits to detect if there is a fire or not
  • In an event that there is a fire and smoke enters the alarm system it goes to the chamber and interrupts the beam going back and forth and the triggers the photocell to get no light and that causes the the electric current to stop working,and so the circuit stops and notices this right away and it sends a trigger to the alarm causing the alarm system to go off

Light Scattering/Use of Energy and Matter

Light scattering is a huge part of optical alarms as it one of they elements that they use to try detect the fire so lets learn more about. Light scattering is the form of scattering in which light is extended to broader area in the form of energy,it can also be thought of as deflection which is the change in a object of a ray from a straight path. Most of the objects that many see are due to the light scattering off the surface. Scattering also often depends on the wavelength and/or frequency of the light. In simpler terms it is when light hits an object and changes its direction, but in some rare cases the light can disappear when once it has made contact with the object and that is called absorption . This also hits the topics of how matter and energy interact and are transferred through systems because in optical alarms because it basically runs on energy and matter also plays a part. Because scattering only works when light makes contact with matter ( particles or molecules) and the light beam in the alarms is constantly doing this and the scattering process involves energy because the light becomes energy.

Negative and Positive Social Impacts of Optical Alarms

There are many benefits of optical alarms as they are able to alert us of fires. About 96% of Canadian households have fire alarms and they have proved to save many lives. You might think if there was a fire you would be aware from the smells and in some cases that is true because when you are awake you could easily spot the fire,but at night it is very difficult for many of the occupants of the house to get up due the the chemical filled air and fumes and in these cases it is when you need something like a loud noise to wake them out of the deep sleep induced by the fires chemicals . This is where the optical alarm would be able to pick up that there is a fire due to the smoke in the air and be able to wake you up. There had been problems in the past when those who were deaf were not able to hear the fire alarms causing many injuries and deaths in the past but optical alarms now are very inclusive and modern because they understand the need for everyone to be safe and found a solution. There are now alarms for those are deaf and unable to hear the alarm,this is when light comes into play because during the physics unit I was able too learn about types of light and there used in different solutions and such. The fire alarms for those who are deaf use a strobe light or a LED light because of how strong the lights power is and the length of how long the light can keep working so the victim in danger can see the light and be aware of the fire taking place and contact fire fighters. Normal optical alarms also contain LED lights as it is a key component. Also some optical alarms for the deaf come with alert-er to the bed for example if the person is sleeping and can not wake up the device will vibrate the bed notifying the occupant of the fire too along with the lights.

Though a lot of the social impacts are positive for optical alarms they do have there negatives and downsides. There has been complaints of noise pollution because the alarms malfunctioned and the alarm not shutting off. In recent years there have been discoveries that fire alarms contained amounts of radioactive materials,to be more specific americium and this can be dangerous is it is inhaled or ingested so for example in a fire you could inhale this chemical if the alarm catches on fire too which could be likely if the fire was very serious,but those are only in ionization alarms. Another reason this could be dangerous is if you were to dismantle and take apart the system which would cause you to inhale the chemical. In test done on fire alarms ionization alarms responded 30-90 seconds faster to fast flame fires than optics alarms however in smoldering fires ionization alarms responded an average 15-20 mins slower than photoelectric alarms. Several studies have shown that ionization alarms will outright fail to activate 20-25% of the time. The huge majority of residential fire fatalities are due to smoke inhalation not from the actual flames and two-thirds of fire fatalities occur during night. 90% of alarms are ionization and only 5% are optical. "Smoldering fires are the early stages of a fire,before open flames develop according to skip walker(2012). This means that there should be change and more households should have optical alarms as they are able to detect the early stages of a fire before it even takes place.

Positive and Negative Environmental Impacts of Optical Alarms

There are many positive sides to having an optical alarms, for example if a fire was to take place in a household the optical alarm would still have a huge impact because even if it was not able to stop the fire it would at least be able to alert the residents in the home of whats taking place and they could call the fire fighters who could come extinguish the fire and help it from getting bigger and further spreading around the area and destroying it

The negative environmental effects of optical alarms are that the optical alarm was to fail to work and alert the home occupants of the fire and it could potentially spread break through out the area and ruin the area, as homes could possibly have been destroyed.

Positive and Negative Environmental Impact Of Optical Alarms

The positive effects of optical alarm are that they save money. This is because optical alarms have the power to alert home/land owners of a fire and it saves them thousands of dollars because if a fire was to happen not only the emotional impact it would have on an individual or family but the money they would have to spend to repair there house or even purchase a new one. In some cases a small fire could spread out and even damage whole streets.It has been said that 90% of residential fires could of been preventable.

Connections To The Physics Unit

  • The first lesson it connects to is light and electromagnetic spectrum lab,this relates to optical alarms because of how light plays a huge part in optical rays because it is the key component of how it works because the light reflects back in the optical alarms to detect smoke. Also the light in the alarm is red meaning it is not visible to the human eye.
  • The second lesson it has connections to is the types of light and there uses area because optical alarms run of a Red LED infra light and it is the reason it can detect fires happening, also for those who are deaf and cannot hear the alarm go off there is versions where strobe lights or Led lights are used to aware the occupants of the fire by flashing on and off repeatedly. Strobe lights and Led lights are chosen because they are lower in power consumption and have a long life span meaning they can run any time any where and the occupant wouldn't need to worry about the filament running out.
  • coThe third unit this topic relates to is convex and concave mirrors, this is because how light reflects off the mirrors and goes into many directions. The same could be said about how the LED light in the optical alarm because it uses the light scattering principle to check if there is a fire taking place. The led light moves back and forth because the light keeps reflecting. In convex and concave mirrors light can also be reflected, convex focus on reflecting light outwards and concave reflects lights inwards so if you were to put the two in front of each other they would work in a similar way.
  • Over all this is how the units connect to the final project.

A photon checks into a hotel and is asked if he needs any help with his luggage.

"No, I'm travelling light"

The End, thank you for taking your time to read this page.

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