Smoke detectors come in two main types - ionization and photoelectric - that use different sensing methods to detect smoke particles. Ionization detectors detect changes in air conductivity using a radioactive source, working best for small particle fires. Photoelectric detectors use light scattering or blocking to detect particles, functioning across a variety of fire types. Smoke detectors are used in homes and buildings to detect fires early and notify occupants, being placed in recommended locations like bedrooms and hallways. While both detector types are effective, ionization models have been shown to respond fastest overall.

1. SMOKE DETECTOR
I N T R O D U C T I O N TO M E C H AT R O N I C S
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2. SOURCE AND CONTROL
•Main controller is considered as the brain of
the system, provides power to the system,
monitors inputs and controls outputs through
various circuits, performs other functions as
required by the appropriate code
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3. WHAT IS SMOKE DETECTOR ?
•A smoke detector is a device
that senses smoke, typically
as an indicator of fire
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4. WHO INVENTED SMOKE DETECTOR ?
Inventor: Francis Upton and his partner Fernando
Dibble filed
Date of invention: March 24, 1890,
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5. WHERE DO WE USE IT ?
 Detect fire in the areas.
 Notify building occupants to take evasive action to escape the dangers
of a hostile fire.
 Summon organized assistance to initiate or assist in fire control
activities.
Initiate automatic fire control & suppression systems & to sound alarm.
 Supervise fire control & suppression systems to assure operational
status is maintained Initiate auxiliary functions involving environmental,
utility & process controls
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6. Smoke detector consists of two parts:
A sensor to sense the presence of smoke particles
An Actuator/Alarm to be triggered
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7. TYPES OF SMOKE DETECTOR
There are two types of smoke detectors
Ionization smoke detector
Photoelectric smoke detector
Both works on different principles to sense visible or invisible
particles of combustion in air given off developing fire.
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8. IONIZATION
SMOKE
DETECTOR
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9. IONIZATION SMOKE DETECTOR
• The ionization smoke detector consists of an alpha particle
producing a radioactive source (americium-241), a smoke chamber,
and charged detector plates.
• The alpha source causes the air within the smoke chamber to
become ionized and conductive.
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11. As smoke particles enter the smoke chamber, the smoke
particles attach themselves to the ionized air molecules
and the air in the chamber becomes less conductive.
When the air conductivity within the chamber drops below
a predetermined level, the alarm is triggered
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12. The ionization smoke detector is widely used. Its
capability to detect smoke originating from fire is
best utilized for clean-burning fires that produce
small particles during combustion.
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13. PHOTOELECTRIC
SMOKE
DETECTOR
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14. PHOTOELECTRIC SMOKE DETECTOR
• The photoelectric type detector utilizes light as a detection mechanism.
• A photoelectric, or optical, smoke detector contains a source of infrared,
visible, or ultraviolet light, a lens, and a photoelectric receiver (typically a
photodiode).
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15. There are two types of photoelectric smoke detectors:
• Light sensing(scattering)
• Light obscuring(blocking
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16. LIGHT SCATTERING SMOKE DETECTOR
• Light scattering smoke detector depend on the ability of small
airborne particles to scatter light.
• The light emitted from the light source is not detected by the photo
sensor.
• When smoke particles enter in the chamber increases, more light is
scattered toward the sensor.
.
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19. LIGHT OBSCURING SMOKE DETECTOR
(BEAM SMOKE DETECTOR)
• It consists of separate light source and a photosensitive
sensor.
• These devices are usually installed in large open areas where
there is an unobstructed line of sight between the light
source and the receiver and where the use of spot-type
detectors would be economically unfeasible due to the
number of detectors required.
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22. WHERE YOU CAN PLACE A DETECTOR?
Bed
room
Basement
Hallway
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23. WHICH IS THE BEST AMONG ABOVE
DISCUSSED ??
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24.  US National Institute of Standards and Technology recognized
ionization smoke detector as having better response rate then others
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25. THANKS
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