3. A mechanical device that is sensitive to
smoke or particular material in the air
that transmits a signal to the measuring
instrument.
Smoke detector consists of two parts:
A sensor to sense the smoke .
Electronic horn to horn the people
5. The photoelectric type detector utilizes light as a
detection mechanism
There are two types of photoelectric smoke
detectors
Light sensing(scattering)
Light obscuring(blocking)
6. Light scattering smoke detector depend on the
ability of small airborne particles to scatter light.
Scattering is due to the
absorption, reflection, refraction, polarization, and
diffraction.
7. 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.
When the concentration of particles reach the
threshold , an alarm sound is produced.
8. LIGHT OBSCURING SMOKE DETECTOR
A projected beam can use a single light source to
and photo sensor to detect a very large area
Most such detectors use IR-LED or laser diode as a
sensor.
Detection of smoke by attenuated light.
Uses a separate emitter and detector.
9. IONIZATION SMOKE DETECTOR
Have ionization chamber inside the detector.
Ionization is very simple two plate chamber with
voltage across along them along with the
radioactive source of ionization.
12. R1-300 ohms
LED-white or any high intensity LED
LDR
R3-100k potentiometer
R2-10 kilo-ohms
Q1-2N222,cs9013, or similar NPN
transistor
R4-1.2 kilo-ohms
R5-1.2 kilo-ohms
Q2-cs9012, any general purpose PNP
transistor
C2-10nF
15. The LED will light up the light
dependent resistor (LDR ) and
making its resistance very low (as
low as 500 ohms). In this
case, transistor Q1 and Q2 are off.
When there is smoke in the
area, light from LED will be blocked
resulting to an increase in LDR
16. The circuit that is installed in the detector is upto the
standards of the electronics-I
All learning techniques were implemented in the circuit.
Polished our abilities.
