Description. Here is a simple fire alarm circuit based on a LDR and lamp pair for sensing the fire.The alarm works by sensing the smoke produced during fire.The circuit produces an audible alarm when the fire breaks out with smoke. When there is no smoke the light from the bulb will be directly falling on the LDR.The LDR resistance will be low and so the voltage across it (below .6V).The transistor will be OFF and nothing happens.When there is sufficient smoke to mask the light from falling on LDR, the LDR resistance increases and so do the voltage across it.Now the transistor will switch to ON.This gives power to the IC1 and it outputs 5V.This powers the tone generator IC UM66 (IC2) to play a music.This music will be amplified by IC3 (TDA 2002) to drive the speaker.Resistor R6 is meant for protecting the transistor when R4 is turned towards low resistance values .Resistor R2 and R1 forms a feedback network for the TDA2002 and C1 couples the feed back signal from the junction of R1 & R2 to the inverting input of the same IC. The diode D1 and D2 in combination drops 1.4 V to give the rated voltage (3.5V ) to UM66 .UM 66 cannot withstand more than 4V. Notes. The speaker can be a 32Ω tweeter. POT R4 can be used to adjust the sensitivity of the alarm. POT R3 can be used for varying the volume of the alarm. Any general purpose NPN transistor(like BC548,BC148,2N222) can be used for Q1. The circuit can be powered from a 9V battery or a 9V DC power supply. Instead of bulb you can use a bright LED with a 1K resistor series to it. This circuit warns the user against fire accidents. It relies on the smoke that is produced in the event of a fire. When this smoke passes between a bulb and an LDR, the amount of light falling on the LDR decreases. 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. Different COBs are available in the market to generate different sounds. The choice of the COB depends on the user. The signal generated by COB is amplified by an audio amplifier. In this circuit, the audio power amplifier is wired around IC TDA 2002. The sensitivity of the circuit 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. An ON/OFF switch is suggested to turn the circuit on and off as desirable. Security and fire alarm systems are designed for operation within specified current and voltage ratings. If these ratings are exceeded, due to short-circuit or voltage transients, components may sustain permanent damage and the equipment may fail. Power supplies and circuit traces must also be protected against faults that may occur during installation or in the case of a shorted back-up battery. Modems are frequently utilized in security systems to automatically alert the fire or police department in an emergency. These telecom lines must be protected from damage caused by lightning strikes, power-line crosses or AC power induction. Alarm systems must comply with the UL864 standard, which mandates that soldered-in fuses are not allowed to qualify a power supply as inherently limited. If the system has provisions for connection to a telephone line it must comply with UL60950 and TIA 968-A in North America, as well as ITU K.21 in Europe and other parts of the world. Overcurrent Protection Options Fuses have typically been used for overcurrent protection in security and alarm systems. However, UL864 and UL60950 pose difficult challenges for these devices, which can fatigue under certain test conditions. More importantly, fuses are single-use components that must be replaced after a fault occurs. Many equipment manufacturers prefer resettable polymeric positive temperature coefficient (PPTC) device protection. Unlike fuses, these devices generally do not require replacement after a fault event, and allow the circuit to return to normal operating condition after the power has been cycled and the overcurrent condition is eliminated. The TDA2003 is a cheap amplifier that is designed to run on single rail power supplies. It has many applications (including in car systems if you do not need to show off down the high street with your subwoofers!) and is protected against short circuits in almost every way you would think them possible. The circuit is very simple as can be seen, however you will have problems with stripboard mounting due to its irritating pin layout. It is possible, but you will find this amp A LOT easier to build on a PCB. Unfortunately, the PCB layout suggestion in the datasheet is a copy of the bridge version suggested layout below it for some reason, so make sure you don't copy it and design your own. If you must use stripboard however, this is how I would mount them. First straighten all the pins, then cut them to the length of the shortest two. Now you need to spread them out so they will fit into the stripboard. Do not spread them too much or they will break and your TDA2003 chip becomes useless. UM66 The UM66 is an electronic doorbell. It requires a botton for the door, a single transistor, a battery and a speaker. It will generate a music signal by taking a less voltage at its input side.we can use it in our commercial applications. musical 3 pin IC UM66 and a popularly known Transistor BC548b IC7805 Encapsulated in a single chip/package (IC), the 7805 is a positive voltage DC regulator that has only 3 terminals. They are: Input voltage, Ground, Output Voltage. Although the 7805 were primarily designed for a fixed-voltage output (5V), it is indeed possible to use external components in order to obtain DC output voltages of: 5V, 6V, 8V, 9V, 10V, 12V, 15V, 18V, 20V, 24V. Note that the input voltage must, of course, be greater that the required output voltage, so that it can be regulated downwards. General Features: Output Current up to 1A Output Voltages of 5, 6, 8, 9, 10, 12, 15, 18, 24V Thermal Overload Protection Short Circuit Protection Output Transistor Safe Operating Area Protection An automatic fire alarm system is designed to detect the unwanted presence of fire by monitoring environmental changes associated withcombustion. In general, a fire alarm system is classified as either automatically actuated, manually actuated, or both. Automatic fire alarm systems are intended to notify the building occupants to evacuate in the event of a fire or other emergency, report the event to an off-premises location in order to summon emergency services, and to prepare the structure and associated systems to control the spread of fire and smoke. Design After the fire protection goals are established - usually by referencing the minimum levels of protection mandated by the appropriate model building code, insurance agencies, and other authorities - the fire alarm designer undertakes to detail specific components, arrangements, and interfaces necessary to accomplish these goals. Equipment specifically manufactured for these purposes are selected and standardized installation methods are anticipated during the design. In the United States, NFPA 72, The National Fire Alarm Code is an established and widely used installation standard. Fundamental configuration A Honeywell DeltaNet FS90 fire alarm control panel. Fire alarm control panel: This component, the hub of the system, monitors inputs and system integrity, controls outputs and relays information. Primary Power supply: Commonly the non-switched 120 or 240 Volt Alternating Current source supplied from a commercial power utility. In non-residential applications, a branch circuit is dedicated to the fire alarm system and its constituents. "Dedicated branch circuits" should not be confused with "Individual branch circuits" which supply energy to a single appliance. Secondary (backup) Power supplies: This component, commonly consisting of sealed lead-acid storage batteries or other emergency sources including generators, is used to supply energy in the event of a primary power failure. Initiating Devices: This component acts as an input to the fire alarm control unit and are either manually or automatically actuated. Examples would be devices like pull stations or smoke detectors. Fire Alarm on a street in San Francisco. Notification appliances: This component uses energy supplied from the fire alarm system or other stored energy source, to inform the proximate persons of the need to take action, usually to evacuate. This is done by means of a flashing light, strobe light, electromechanical horn, speaker, or a combination of these devices. Building Safety Interfaces: This interface allows the fire alarm system to control aspects of the built environment and to prepare the building for fire and to control the spread of smoke fumes and fire by influencing air movement, lighting, process control, human transport and exit. Initiating devices Manually actuated devices; Break glass stations, Buttons and manual pull station are constructed to be readily located (near the exits), identified, and operated. Automatically actuated devices can take many forms intended to respond to any number of detectable physical changes associated with fire: convected thermal energy; heat detector, products of combustion; smoke detector, radiant energy; flame detector, combustion gasses;carbon monoxide detector and release of extinguishing agents; water-flow detector. The newest innovations can use cameras and computer algorithms to analyze the visible effects of fire and movement in applications inappropriate for or hostile to other detection methods. Notification appliances Main article: Fire alarm notification appliance A Honeywell speaker and a Space Age Electronics V33 remote light. Audible, visible, tactile, textual or even olfactory stimuli (odorizer).  to alert the occupants. Evacuation signals may consist of audible or visible appliances with a distinct audible tone or speakers to deliver live or pre-recorded instructions to the occupants. In the United States, fire alarm evacuation signals generally consist of a standardized temporal code 3 audible tone, with visual notification in all public and common use areas. Emergency signals are intended to be distinct and understandable to avoid confusion with other signals. Other methods include: Audible textual appliances, which are employed as part of a fire alarm system that includes Emergency Voice Alarm Communications (EVAC) capabilities. High reliability speakers are used to notify the occupants of the need for action in connection with a fire or other emergency. These speakers are employed in large facilities where general undirected evacuation is considered impracticable or undesirable. The signals from the speakers are used to direct the occupant's response. The system may be controlled from one or more locations within the building known as Fire Wardens Stations, or from a single location designated as the building Fire Command Center. Speakers are automatically actuated by the fire alarm system in a fire event, and following a pre-alert tone, selected groups of speakers may transmit one or more prerecorded messages directing the occupants to safety. These messages may be repeated in one or more languages. Trained personnel activating and speaking into a dedicated microphone can suppress the replay of automated  messages in order to initiate or relay real time voice instructions. Emergency Voice Alarm Communication Systems Some Fire Alarm Systems utilize Emergency Voice Alarm Communication Systems (EVACS)  to provide pre-recorded and manual voice messaging to building occupants. Voice Alarm systems are typically used in high-rise buildings, arenas and other large "defend-in-place" occupancies such as Hospitals and Detention facilities where total evacuation is difficult to achieve. Voice-based systems are especially useful during fire, security, weather and similar events, and provide response personnel with the ability to conduct orderly evacuation and notify building occupants of changing event circumstances. Building safety interfaces This section does not cite any references or sources. Please help improve this article by adding citations to reliable sources. Unsourced material may be challenged and removed. (January 2011) S.H. Couch F5GX non-coded fire alarm pull station below a Couch 10" bell. Magnetic Smoke Door Holders: Wall or floor mounted solenoids or electromagnets controlled by a fire alarm system or detection component that magnetically secures spring-loaded self-closing smoke tight doors in the open position. Designed to de-magnetize to allow automatic closure of the door on command from the fire control or upon failure of the power source, interconnection or controlling element. Stored energy in the form of a spring or gravity can then close the door to restrict the passage of smoke from one space to another in an effort to maintain a tenable atmosphere on either side of the door during evacuation and fire fighting efforts. Duct Mounted Smoke Detection: Smoke detection mounted in such a manner as to sample the airflow through duct work and other plenums specifically fabricated for the transport of environmental air into conditioned spaces. Interconnection to the fan motor control circuits are intended to stop air movement, close dampers and generally prevent the recirculation of toxic smoke and fumes produced by fire into occupiable spaces. Emergency Elevator Service: Activation of automatic initiating devices associated with elevator operation are used to initiate emergency elevator functions, such as recall of associated elevator cab(s). Recall will cause the elevator cabs to return to the ground level for use by fire service response teams and to ensure that cabs do not return to the floor of fire incidence. Phases of operation include primary recall (typically the ground level), alternate/secondary recall (typically a floor adjacent to the ground level - used when the initiation occurred on the primary level), illumination of the 'fire hat' indicator when an alarm occurs in the elevator hoistway or associated control room, and in some cases shunt trip (disconnect) of elevator power (generally used where the control room or hoistway is protected by fire sprinklers).
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