Heat Detector Essay Example for Free

Heat Detector Essay When present, humans can be excellent fire detectors. The healthy person is able to sense multiple aspects of a fire including the heat, flames, smoke, and odors. For this reason, most fire alarm systems are designed with one or more manual alarm activation devices to be used by the person who discovers a fire. Unfortunately, a person can also be an unreliable detection method since they may not be present when a fire starts, may not raise an alarm in an effective manner, or may not be in perfect heath to recognize fire signatures. It is for this reason that a variety of automatic fire detectors have been developed. Automatic detectors are meant to imitate one or more of the human senses of touch, smell or sight. Thermal detectors are similar to our ability to identify high temperatures. The properly selected and installed automatic detector can be a highly reliable fire sensor. Our automatic fire alarm system is designed to detect the unwanted presence of fire by monitoring environmental changes associated with combustion. In general, our 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. Whenever the system detects a high temperature, the fire alarm will inform the area and send a text message to the fire station and will inform them the specific block/area in the subdivision which is on fire. GSM/GPRS module is used to establish communication between a computer and a GSM-GPRS system. Global System for Mobile communication (GSM) is an architecture used for mobile communication in most of the countries. In our system, we will be using GSM modem Nokia 6300 for the output of text. The device will send a text message to the nearest fire station and will inform which house is on fire. Control Panel The control panel is the brain of the fire detection and alarm system. It is responsible for monitoring the various alarm input devices such as manual and automatic detection components, and then activating alarm output devices such as horns, bells, warning lights, emergency telephone dialers, and building controls. Control panels may range from simple units with a single input and output zone, to complex computer driven systems that monitor several buildings over an entire campus. Upon fire occurrence, one or more detectors will operate. This action closes the circuit, which the fire control panel recognizes as an emergency condition. The panel will then activate one or more signaling circuits to sound building alarms and summon emergency help. The panel may also send the signal to another alarm panel so that it can be monitored from a remote point. Alarm Output Devices Upon receiving an alarm notification, the fire alarm control panel must now tell someone that an emergency is underway. This is the primary function of the alarm output aspect of a system. Occupant signalling components include various audible and visual alerting components, and are the primary alarm output devices. All fire alarm systems require notification devices, including sirens, bells, horns, and/or strobes. In residential applications, each automatic alarm initiating device when activated shall cause the operation of an alarm notification device that shall be clearly audible in all bedrooms over ambient or background noise levels (at least 15dB above noise) with all intervening doors closed. Bells are the most common and familiar alarm sounding device, and are appropriate for most building applications. Horns are another option, and are especially well suited to areas where a loud signal is needed such as library stacks, and architecturally sensitive buildings where devices n eed partial concealment. In this case, we will be using Siren as the alarm output device. Some of the major benefits of installation of fire alarms are as follows. †¢ Safety is the most important reason why we should have fire alarms in our house, even before a fire breaks out, the smoke detectors tell you there is a possibility of a fire and you can safely be out of danger. Secondly being pre informed about a possible fire, a prompt message can be conveyed to the fire workers. As a result of this, damage can be minimized and valuables can be saved from being burnt to ashes. †¢ A house with a fire alarm is a safer house and fetches a far better price in the real estate market. The customers feel secured when they see that they are opting for a property that has the safety measures installed. †¢ Using a fire alarm is a cost effective way to ensure that your assets are not in danger. Being noted beforehand you can move them out quickly thus saving your valuables from being burnt. †¢ The alarm works even when nobody is in the house and thus alerts the neighbours. This way your home can be protected from any major damages. Limitations of our Heat Sensor †¢ Heat detectors do not sense particles of combustion and are designed to alarm only when heat on their sensors increase at a predetermined rate or reaches a predetermined level. Heat detectors are designed to protect property, not life. †¢ Warning devices (including horns, sirens, and bells) may not alert people or wake up sleepers who are located on the other side of closed or partially open doors. A warning device that activates on a different floor or level of a dwelling or structure is less likely to awaken or alert people. Even persons who are awake may not notice the warning if the alarm is muffled by noise from a stereo, radio, air conditioner or other appliance, or by passing traffic. Audible warning devices may not alert the hearing-impaired (strobes or other devices should be provided to warn these people). Any warning device may fail to alert people with a disability, deep sleepers, people who have recently used alcohol or drugs, or people on medication or sleeping pills. Temperature Sensor The Thermistor Thermistors are temperature sensitive resistors. All resistors vary with temperature, but thermistors are constructed of semiconductor material with a resistivity that is especially sensitive to temperature. However, unlike most other resistive devices, the resistance of a thermistor decreases with increasing temperature. Thats due to the properties of the semiconductor material that the thermistor is made from. A Thermistor is a temperature dependent resistor. When temperature changes, the resistance of the thermistor changes in a predictable way. Sensor Advantages and Disadvantages [pic] Each sensor type has advantages and disadvantages. For thermistors, the major advantages are: Sensitivity: This allows thermistors to sense very small changes in temperature. Accuracy: Thermistors offer both high absolute accuracy and interchangeability. Cost: For the high performance they offer, thermistors are very cost-effective. Ruggedness: Because of their construction, thermistors are very rugged. Flexibility: Thermistors can be configured into a wide variety of physical forms, including very small packages. Hermetic Seal: Glass encapsulation provides a hermetic package, eliminating moisture induced sensor failure. Surface Mount: A wide range of sizes and resistance tolerances are available. Of the thermistor disadvantages, typically only self-heating is a design consideration. Proper care must be taken to limit the sensing current to a low enough value that self-heat error is minimized to an acceptable value. Types of Thermistors Thermistor Elements The thermistor element is the simplest form of thermistor. Because of their compact size, thermistor elements are commonly used when space is very limited. OMEGA offers a wide variety of thermistor elements which vary not only in form factor but also in their resistance versus temperature characteristics. Since thermistors are non-linear, the instrument used to read the temperature must linearize the reading. Linear Response Thermistor Elements For applications requiring thermistors with linear response to temperature change, OMEGA offers linear components. These unique devices consist of a thermistor composite for temperature sensing and an external resistor composite for linearizing. Thermistor Probes The standalone thermistor element is relatively fragile and cannot be placed in a rugged environment. OMEGA offers thermistor probes which are thermistor elements embedded in metal tubes. Thermistor probes are much more suitable for industrial environments than thermistor elements. Resistance Temperature Detector (RTD) RTDs (Resistive Temperature Detectors) serve as the standard for precision temperature measurements due to their excellent repeatability and stability characteristics. RTDs provide the designer with an absolute result that is fairly linear over temperature. The RTD’s linear relationship between resistance and temperature simplifies the implementation of signal conditioning circuitry. The RTD requires external current excitation, as well as signal conditioning to account for lead wire effects and self-heating. Analog Devices supplies the ADT70, which provides both excitation and signal conditioning for a platinum RTD. The output of this device (5 mv/ °C) is be fed through an analog to digital converter, to be converted by the DSP to temperature readings.