The reference to paragraph 37 sensors and modules, widely circulated on the Internet, in fact, compatible with Arduino sensor module must be more than 37 species. Since I am on hand accumulated a number of sensors and modules, in accordance with the concept of practice makes perfect (try hands), in order to learn and exchange for the purpose of preparing one by one here doing the experiment, regardless of success, will be recorded --- small progress or can not handle the problem, hoping to initiate.
[] Arduino series of experiments, the sensor module 108 kinds (information + + graphics + Simulation Code)
Experimental seventeen: HC-SR312 human pyroelectric sensor miniature sensor module
Pyroelectric effect
In some insulating material, due to temperature changes caused by changes in polarization state of a phenomenon referred to pyroelectric effect. Substances can achieve the pyroelectric effect of pyroelectric material is referred to. Three pyroelectric substance sulfate GSH (the TGS), a ferroelectric barium titanate, tourmaline and sucrose. This phenomenon as early as 2300 years ago was discovered, but its research began in the 18th century. Now it has become one of the most active in solid state physics research. Because the pyroelectric coefficient of the ferroelectric pyroelectric element is much greater than the average, it became widely used of the thermoelectric material, in addition to TGS and derivatives thereof, ferroelectric ceramics (such as PZT, PLZT, etc.) become easily by changing the component practical control performance thermoelectric material, suitable for mass production and inexpensive.
Is used for the pyroelectric effect of pyroelectric infrared detector in the last 10 years, radiation and widely used non-contact temperature measurement, infrared spectroscopy, measurement of laser parameters, industrial automation, space technology, in the infrared imaging. China's use of crystal made ATGSAS infrared camera tube has begun to export abroad. Its temperature response rate of 4 ~ 5μA / ℃, less than 0.2 deg.] C temperature resolution, high sensitivity signal, image clarity and anti-glare interference also significantly improved, and the hysteresis is small. In addition, because there are organisms pyroelectric phenomenon, it can be expected pyroelectric effect will have important applications in biology, and even the life course.
Pyroelectric element
Pyroelectric element (probe) has a variety of models, but the structure, substantially the same shape and electrical parameters, generally by the sensing element FET, and the filter window impedance converter or the like, and packaged under nitrogen.
Pyroelectric infrared sensors incorporated in the structure of the FET, and its object is to complete the impedance transformation. Since the pyroelectric element outputs the charge signal, and can not be used directly, thus requiring a resistor to convert it into a voltage form. Therefore, N-channel junction field effect is introduced into the tube should be connected to form a common drain impedance transformation is completed. Pyroelectric infrared sensors to detect by the sensing element, an interference filter and a three-part composition FET matcher. The design should be made of a high thermoelectric material sheet of a certain thickness, and its both surfaces coated with a metal electrode, and then subjected to polarizing power, so that it is made of a pyroelectric detection element.
Fresnel lens optics using a special lens, a generating alternating in front of the detector "blind" and "sensitive areas", to increase its reception sensitivity detection. When someone walked from the front lens, infrared body have continued alternately emitted from the "dead zone" into the "sensitive areas", so that the received infrared signal in a pulse form strong suddenly weak suddenly input, thereby enhancing the amplitude of its energy . Body center wavelength of the infrared radiation 9 ~ 10 - um, the wavelength sensitivity of the detection element in the 0.2 ~ 20-- almost constant within a stable range um. Window opened at the top sensor with a filter lens, the wavelength range of light through the filter is 7 ~ 10 - um, exactly adapted to detect infrared radiation, while the other wavelengths to infrared filter sheet to be absorbed, thus forming a sensor exclusively used for detecting infrared radiation in the human body.
Features pyroelectric infrared sensor is, only when the radiation due to external temperature changes caused by itself, it gives a corresponding electrical signal, when the change in temperature has stabilized, the signal is no longer output. Therefore, the heat release rate of temperature change and an electric signal proportional to itself, i.e., only the pyroelectric sensor sensitive to human motion. Typically, the sensitive cell material has very high impedance, so the impedance transformation for use FET to practical use. The role of the circuit of the high resistance of resistor Rg is the gate charge is released, so that FET work; When using source output, to an external resistance Rs of the source, the source voltage of approximately 0.4 ~ l.0V. Made sensitive element PZT (lead zirconate titanate) is a spectrum of the material, it can detect various wavelengths of radiation. In order to make the sensor is most sensitive to the human body, while the sun, electric lights, which are anti-interference, do sensor uses a filter window. Filter so that the body radiation of wavelength infrared strongest right on the center of the filter window corresponding wavelength, so can effectively filter window to let the body through infrared radiation, and prevent sunlight, infrared light and other visible light through, so as not to cause interference. To improve the sensitivity of the sensor, a Fresnel lens may be placed at the front of the sensor 1 ~ 5cm, that the detection distance of 2m from the general increase to 10 to 20m. When laboratory tests, may Garfield Fresnel lens. In practical applications, the sensor is often necessary to warm up, which is determined by the sensor itself. Passive infrared detector typically requires about one minute warm-up time.
Pyroelectric infrared sensor disadvantages
advantages:
itself does not send any type of radiation, power dissipation is small, a good hiding. Low prices.
Disadvantage:
◆ susceptible to various heat sources, light interference
◆ PIR penetration is poor, the body of the infrared radiation is easily blocked, the probe can not easily be received.
◆ When the ambient temperature and body temperature close to the detection and sensitivity decreased, sometimes resulting in short-term failure.
Important:
should avoid sunlight, car headlights, an incandescent lamp is irradiated directly, not facing the heat source (such as radiators, heaters) or an air conditioner, in order to avoid large changes in ambient temperature cause false; mounting must be secured to avoid false alarms caused by wind shaking; not allowed to touch the surface of the sensor; an outer surface of the optical lens regularly with a soft cloth or cotton wipe, affect the sensitivity to avoid dust; mounting height 2m.
Some common circuit
| HC-SR312 human sensor module is a miniature electric effect pyroelectric-based, digital intelligent passive infrared technology, automatic body control products, high sensitivity, high reliability, widely used in various auto-sensing electrical equipment.
|
Electrical schematics
Technical Parameters
1. Working Voltage: the DC 2.7-12V;
2. Static power consumption: <0.1mA;
3. Delay time: 2 seconds;
4 blocking time: 2 seconds;
5. Trigger: reusable;
6. Induction range: ≦ 100 degrees cone angle, 3-5 meters; (according to the specific needs of a lens)
7. Operating temperature: -20 - + 60 deg.] C
8.PCB dimensions: 10mm * 8mm
9. the lens module: small lenses
Module pin assignments
Applications
■ ■ body induction lamp body induction toys
■ ■ security products industrial automation and control
■ ■ auto-sensing electrical equipment such as battery-powered automatic control
It features
a, ultra small size, high sensitivity, high reliability, low voltage operation mode.
B, immunity enhancement, the internal digital signal processing, high and low output directly.
C, automatic induction: enter its output high sensing range, the sensing range is automatically leave delay off high, output low.
d, repeatable trigger: the sensor output high after, the delay period, if there is human activity in its sensing range, the output will remain high until after the delay to leave before they become low level (i.e.: a sensing module detects a delay time will be automatically extended period after each event of the human body, and the last time event starting point of delay time). VOUT pin output module switch is, when approaching the sensing module outputs a high level to the low level after the recovery leave. So, any one of which can be accessed microcontroller IO pins are OK, the query method can be used, query the status of the connection pins, you know VOUT pin is high power or low level, thereby judge whether someone close.
Experimental test chart
/*
【Arduino】108种传感器模块系列实验（资料+代码+图形+仿真）
实验十七：HC-SR312微型热释电传感器模块
*/
void setup()
{
pinMode(3,INPUT);
pinMode(13,OUTPUT);
}
void loop()
{
if (digitalRead(3)) {
digitalWrite(13, HIGH);
delay(1000);
}
else
{
digitalWrite(13, LOW);
}
}
