Winnate knowing Xin | One article understands infrared thermal release sensor

The armal release sensor is a sensor that can output electrical signals that can detect people or animals. As early as 1938, some people proposed the use of thermal release effect to detect infrared radiation, but it was not valued. It was not until the 1960s that the research on thermal release effect and the application of thermal -release electrical crystals were raised.

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Objects that exist in nature, such as the human body, flames, ice cubes, etc., will emit infrared rays, but the wavelengths are different. The temperature of the human body is 36-37 ° C, and the infrared wavelengths emitted are 9-10um, which belongs to the far-infrared area; the heating body of 400-700 ° C, the infrared wavelength of infrared ray is 3-5um, which belongs to the middle infrared area. The hot -release infrared sensor is not affected by the day and night. It can be used for monitoring day and night, and is widely used in anti -theft alarm and inductive lights.

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The principle of thermal release sensor

The hot -release infrared sensor is generally composed of the main parts such as tube caps, tube seats, infrared filters, sensitive elements, field effect tubes, or digital chips.

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The spontaneous polarization strength of thermal release material generates the characteristics of the charge movement with the changes in the external temperature, and the changes in infrared energy of the human radiation are detected by non -contact mode, and it is converted into a electrical signal. , And amplify the signal through the power amplifier to achieve the purpose of the control circuit.

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The receiving wavelength of the infrared filter window material:

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5.5um long wave pass filter light spectrum chart

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The above figure shows the reference map of a typical 5.5um long wave pass infrared filter. The curve is the average value of infrared passage rate. The window material is a semiconductor silicon wafer that has been treated with special vacuum coating.

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Category of thermal release sensor

Depending on the signal processing circuit, the hot -release infrared sensor can be divided into two types: simulation and digital.

The signal processing circuit of the simulation thermal -release infrared sensor is the field effect tube, and the signal processing circuit of the digital hot -release infrared sensor is a digital chip.

Simulation thermal release sensor

RD623/RD624

High -sensitivity and superior signal -to -noise ratio

High stability of temperature changes;

Strong anti -interference ability (such as vibration, radio frequency interference, etc.);

Excellent cost -effective;

Strong anti -white light ability.

Digital thermal release sensor

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RDB223/RDB224

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High -precision AD signal processing;

Differential signal input method, strong anti -interference ability;

With sensitivity adjustment, delay time adjustment, light sensitivity to control the control function;

Power supply of wide voltage domain 1.5 ~ 4.5V, low power consumption;

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Digital TTL signal output.

The characteristics of thermal release sensor

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The hot -release infrared sensor can only play the maximum role with Fresnel lens.

When not combined with Fresnel lens, the detection radius of the sensor may be less than 2 meters, and the Fresnel lens can reach 10 meters or even farther. Fresnel lens is made of general polyethylene and installed in front of the sensor.

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The principle of Fresnel lens lens is shown in the figure below:

When the light passes through the lens unit, it forms a bright and dark area and blind spots in the opposite side. Each lens unit has only a small field angle. The visible area in the field of view and the blind area. By changing the temperature of the infrared radiation in the human body in the bright and dark region, the temperature of the sensitive element of the thermal terminal is changed, so that it outputs the corresponding weak electrical signals after another.

The frequency of the output signal is about 0.1 ~ 10Hz. This frequency range is determined by the characteristics of Fresnel lens, human motion speed, and thermal emigrase infrared sensor itself.

Application of thermal release sensor

Heat -release infrared sensors are currently mainly used in home security, smart office, smart lamps, inductive switches, smart home, smart doorbell, invasion detection, inductive toys, smart home appliances, automated control and other fields.

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