Electronics Fire Alarm using NE555 and temperature sensor

Circuit Fire alarm using NE555 and temperature sensor schematics Circuit Electronics,

This is a simple series of fire alarms. In this series used NE555 timer and temperature sensor to detect high temperatures. The working principle of this temperature sensor that is when the temperature is high around the sensor then there is resistance on the sensor to be small.

However if the low temperature then the resistance will be high. If the resistance of small sensors, the voltage supply will be able to flow past the sensor and activate the transistor.

IC1 NE555 as a regulator of the audio frequency. Transistors 1 and 2 are used as a driver IC1. Output (pin 3) of IC1 would trigger a transistor base T3 (SL100), which drives the speaker to produce sound the alarm. Frequency NE555 depending on resistance values ​​of R5 and R6 and the capacitance sensor C2 temperature. When the temperature gets hot, would provide a low resistance so that supply voltage can flow into the base of transistor T1 through a diode D1 and R2.

Capacitor C1 will charge a positive voltage so that it will increase the time when the fire alarm. The greater the value of C1, the greater the positive bias applied to the base of transistor T1 (BC548). T1 collector coupled to the base transistor T2, transistor T2 provides a positive voltage to pin 4 (reset) from IC1 (NE555). Resistors R4 will make IC1 NE555 continued to be active despite no positive voltage flowing.

Schematics for Fire alarm using NE555 and temperature sensor Circuit Electronics

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Electronics Temperature and Humidity Sensor

Circuit Temperature and Humidity sensor schematics Circuit Electronics,

Temperature and humidity sensors used are SHT75. This sensor is a chip that can measure temperature and humidity as well. The use of these sensors with consideration of its small size and reliability. The output of this sensor has the form of digital data in the chip because it has been there for a 14bit ADC.

Temperature measurement range between -40-123,8 º C and humidity between 0-100% Rh. Measurement accuracy reaches ± 0.3 per increase of 25 º C for temperature and ± 1.8% RH for humidity.

Temperature and humidity sensor

The default measurement resolution of this sensor is 14 bits to 12 bits and temperature sensors for humidity sensors, can also use only 12 bit resolution and 8 bits.

Schematics for Temperature and Humidity sensor Circuit Electronics

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Schematics Hearbeat Sensor (Tranducer) Circuit

This is a design circuit of a simple heart-beat transducer. Here’s the figure of the circuit;

 

This circuit made from an infrared phototransistor and infrared LED.  This transducer works with the principle of light reflection, in this case the light is infrared.  The skin is used as a reflective surface for infrared light. The density of blood in the skin will affect on the IR reflectivity. The pumping action of heart causes the blood density rises and falls. So that we can calculate the heart rate based on the rise and fall of intensity of infrared that reflected by skin.

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Schematics AD586/597 Temperature Transducer (Sensor)

That is a design circuit for a stand alone temperature transducer/sensor circuit. This device uses The AD596/AD597, employing its internal junction compensation temperature sensor inside. Here’s the figure of the circuit;

This device can be used as temperature sensor by omitting the thermocouple and connecting the inputs (Pins 1 and 2) to common. The output will reflect the compensation voltage and the AD596/AD597 temperature will be indicated by the output. the AD596/AD597 will be operated over the full extended –55°C to +125°C temperature range. This device has output scaling of 10.1 mV per°C with the AD597 and 9.6 mV per °C with the AD596. When AD596 is used in temperature sensing mode, it will read slightly high, because there is 42mV offset.

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