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
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 depend on theability 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.
R1-300 ohmsLED-white or any high intensity LEDLDRR3-100k potentiometerR2-10 kilo-ohmsQ1-2N222,cs9013, or similar NPNtransistorR4-1.2 kilo-ohmsR5-1.2 kilo-ohmsQ2-cs9012, any general purpose PNPtransistorC2-10nF
c3-2.2uF electrolytic capacitorR6-1.2 kilo-ohmsR7-5 kilo-ohmsC1-100nF555 IC9V battery or DC supplyspeaker (8-ohms )
The LED will light up the lightdependent resistor (LDR ) andmaking its resistance very low (aslow as 500 ohms). In thiscase, transistor Q1 and Q2 are off.When there is smoke in thearea, light from LED will be blockedresulting to an increase in LDR
The circuit that is installed in the detector is upto thestandards of the electronics-I All learning techniques were implemented in the circuit. Polished our abilities.