Smoke Detector

Electronics-I

Group members

Rija Fatima

RajaasTahir

SMOKE DETECTOR

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

Types Of Smoke Detector

Photoelectric smoke Detector

Ionization Smoke Detector

PHOTO ELECTRIC SMOKE DETECTOR The photoelectric type detector utilizes light

as a detection mechanism There are two types of photoelectric smoke

detectors

Light sensing(scattering) Light obscuring(blocking)

LIGHT SCATTERING SMOKE DETECTOR

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.

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.

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.

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.

Photoelectric circuit

Implemented by us

INTERNAL CIRCUIT

System hardware R1-300 ohms

LED-white or any high  intensity LEDLDRR3-100k potentiometerR2-10 kilo-ohmsQ1-2N222,cs9013, or  similar NPN transistorR4-1.2 kilo-ohmsR5-1.2 kilo-ohmsQ2-cs9012, any general purpose PNP transistorC2-10nF

c3-2.2uF electrolytic capacitor

R6-1.2 kilo-ohms

R7-5 kilo-ohmsC1-100nF

555 IC

9V battery or DC supply

speaker (8-ohms)

Circuit Operation

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 resistance. In this case, both transistor are on, and 555 timer starts to generate sound to the speaker.

Why Smoke Detector ?

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.