This home smoke detector circuit warns the user against fire accidents.
It relies on the smoke that is produced in the event of a fire and passes between a bulb and an LDR, the amount of light falling on the LDR decreases. This type of circuit is called optical smoke detector. Do not use it as a home smoke detector it’s jus for electronic projects.
This causes the resistance of LDR to increase and the voltage at the base of the transistor is pulled high due to which the supply to the COB (chip-on-board) is completed. The sensitivity of the smoke detector depends on the distance between bulb and LDR as well as setting of preset VR1. Thus by placing the bulb and the LDR at appropriate distances, one may vary preset VR1 to get optimum sensitivity.
We have not build this smoke alarm detector.
For smoke detector installation and maintenance use a near electrician.
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RE46C190 photoelectric smoke detector – source
Using this photoelectric smoke detector circuit can be designed a very simple and low power smoke detector alarm project that is based on the RE46C190 smoke detector IC . With minimal external components, this smoke detectors alarm circuit will provide all the required features for a photoelectric smoke detector type electronic project.
The design incorporates a gain-selectable photo amplifier for use with an infrared emitter detector pair. An internal oscillator strobes power to the smoke detection circuitry every 10 seconds, to keep the standby current to a minimum. If smoke is sensed, the detection rate is increased to verify an Alarm condition.
The simple schematic diagram of a smoke detector presented here utilizes the gas sensor TGS 813 as the main detecting component. The circuit is pretty easy to build and performs useful fire hazard detection once installed into a possible fire prone zone.
IC1 = 741
IC2 = 7805
T1 = TIP122