LM1801 smoke detector circuit design electronic project


Posted on Feb 6, 2014

This smoke detector electronic project is designed using LM1801 and common electronic parts. Smoke detector circuit diagram below does not use ionization detection, gas or optocouplers it use two photoresistors (LDR`s) and an LED. The circuit uses a pair phototranzistors for compensation which removes any resistance caused by changes in temperatur


LM1801 smoke detector circuit design electronic project
Click here to download the full size of the above Circuit.

e or aging effects. This circuit is made of network bridge R1, R4, two LDR`s (R12, R13) connected to one of the comparator inputs common point of R4 and R13. The other comparator inputs are connected internally to the point of R1 and R2 voltage divider R12 and / R3. This arrangement provides both LDR`s polarization to the same voltage, to achieve accurate tracking. Physically, LDR s should be located so that smoke particles reflect light from the LED (D2) in R3, leading to lower its resistance. Once comparator detects this voltage drop, the integrated circuit commands Th1 triac (SCR) powering siren putting it into operating mode. Circuit sensitivity is adjusted with P1, the LED D2 should be mounted between the two photoresistors at approximately equal distances.




Leave Comment

characters left:

Related Circuits

  • New Circuits

    .

     


    Popular Circuits

    Buffered Crystal VXO
    PIC18 programmer
    10F8-channel-transmission-system
    LM555 interlocked monostable timer circuit
    A Bedside Lamp Timer Circuit Schematic
    active loudness circuit schematic
    simple analog to digital converter
    LT3083 current limiting
    Crystal oscillator
    Simple PIC USB Interface Circuit
    TA2022 and TAS5010 digital amplifier circuit diagram



    Top