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EXSENSE customizes silver / gold electrode NTC chip die, high precision / high temperature NTC thermistor & waterproof / fast response temperature sensor. Application: new energy vehicles / smart home / GSM / OA / medical electronic, infrared thermal / thermal printer head / laser printer & copier / IGBT / optical communication devices / smart toilet / coffee maker / medical device.
    EXSENSE Electronics Technology Co.,Ltd.is specialized in a variety of NTC thermistor NTC temperature sensor devices and related materials research, production, development and sale of private high-tech enterprises.Companies in the industry rely on a strong collaborative capabilities, to provide customers with a variety of electronic components supporting services.
    The use of advanced semiconductor manufacturing process combined with independent intellectual property rights of the NTC temperature sensor, NTC thermistor materials and process technology, through Japan, Taiwan, Germany, imported high-precision materials processing, slicing, packaging and testing equipment, we achieved an NTC thermistor NTC resistor temperature sensor devices and high-precision volume manufacturing. At the same time, through innovative management, strengthening quality control, we ensure the continuous production of products with high stability, high reliability. At this stage of the main species produced include: AT Series-- High Precision Dip NTC ThermistorLT Series-Small Size High Precision Dip NTC Thermistor BT Series–Battery Series High Precision NTC ThermistorDT Series—Die (Bare chip)NTC ThermistorIT Series—Electronic Thermometer Series High Precision NTC ThermistorCT Series–Chip Type NTC ThermistorFT Series–Film Type NTC ThermistorGT Series–Glass Sealed NTC ThermistorPT Series–Power Type NTC ThermistorTS Series–NTC Temperature sensor
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Simple fire alarm- thermistor circuit diagram


Here comes with a simple and automatic fire alarm and detection system. This fire detection alarm circuit is based on thermistor. What is a thermistor? A thermistor is nothing but a variable resistor whose resistance changes with temperature. Fire detection is simply possible via this low-cost alarm circuit.


A simple potential divider arrangement using thermistor is capable of sensing the temperature(presence of fire) and alerting us with a warning signal. This is suitable for your home security systems. Also school students can do this fire detector circuit as their high school science fair projects. Here I will explain in detail about fire alarm circuit wiring with animation/ simulation of fire alarm.


Circuit diagram of simple fire alarm

Components required

1. Power supply
2. Resistors (1kΩ)
3. Potentiometer (10KΩ)
4. Capacitor (10μF, 16V)
5. BC548 transistor
6. High resistance thermistor (NTC)
7. Diode (1N4001)
8. 6V Buzzer


Working of fire alarm circuit

  • Working is based on the switching property of transistor.
  • The thermistor and R1 forms a potential divider network which drives the transistor.
  • The heart of this circuit is a thermistor. Thermistors are low-cost, easily-available temperature sensors widely used for uncomplicated temperature measurements.
  • Thermistors are temperature sensitive resistors. When temperature increases resistance offered by the thermistor decreases and vice versa. At normal temperature, the resistance of the thermistor is around 10kΩ.
  • All resistors vary with temperature, but the semiconductor materials used for thermistors are especially sensitive to temperature.
  • The transistor is turned ON by the voltage drop across the resistor R1.
  • Consider the temperature of the atmosphere is around 25°C, and then the resistance of thermistor is high so the voltage across the thermistor is also high according to the basic ohm’s law V=IR.
  • The threshold voltage can be set by varying the potentiometer (R1).
  • At this situation voltage across resistor R1 is low and it is not sufficient to turn on the transistor.
  • As temperature rises, the resistance of thermistor decreases so that the drop across the resistor R1 increases which turns ON the transistor.
  • When the transistor is turned ON, the current from Vcc starts to flow via 6V buzzer which produces a beep sound.
  • Diode is used for enabling unidirectional conduction and the capacitor removes sudden transients from the thermistor.


Simulation of the fire alarm project

We have used an LED instead of buzzer for the simulation of fire alarm system.

EXSENSE Electronics Technology Co., Ltd.
 

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