The infrared receiving tube is named in the LED industry. It is specially used to receive and sense the infrared light emitted by the infrared transmitting tube. In general, it is used in complete set with infrared emission tube in product equipment.
Features and principles:
Infrared receiving tube is a semiconductor device that turns infrared light signal into electrical signal. Its core component is a special material PN junction. Compared with ordinary diodes, it has taken a big change in structure. In order to receive more and larger incident light, the area of PN junction is larger as far as possible, the area of electrode is smaller as far as possible, and the junction depth of PN junction is very shallow, Generally less than 1 micron. The infrared receiving diode works under reverse voltage. When there is no light, the reverse current is very small (generally less than 0.1 μ a), which is called dark current. When there is infrared light, the infrared photon carrying energy enters the PN junction, and transmits the energy to the bound electrons on the covalent bond, so that part of the electrons break away from the covalent bond, thus generating the electron hole pair (abbreviated as: photo generated carrier). They participate in the drift motion under the action of reverse voltage, which makes the reverse current significantly larger. The greater the intensity of light, the greater the reverse current. This characteristic is called photoconductivity. Infrared receiving diode in the general illumination of light, the current generated is called photocurrent. If the load is connected to the external circuit, the electrical signal will be obtained on the load, and the electrical signal will change with the change of light.
Classification: there are two kinds of infrared receiving tubes, one is photodiode, the other is triode. Photodiode is to convert the optical signal into electrical signal. The triode not only converts the optical signal into electrical signal, but also amplifies the current. Therefore, there are two types of phototriodes, NPN type and PNP type.
Function: the function of the infrared receiving tube is to carry out photoelectric conversion, which is widely used in light control, infrared remote control, light detection, optical fiber communication, photoelectric coupling, etc. How to choose infrared receiver: the most important parameter of infrared is the magnification of photoelectric signal. Generally, there are 1000-1300, 1300-1800, 1800-2500, which determine the sensitivity.
Infrared tube is a general term for the use of infrared transmitting tube and photosensitive receiving tube, or infrared receiving tube, or infrared receiving head. Infrared in the spectrum wavelength from 0.76 to 400 microns is called infrared, infrared is invisible light. All substances above absolute zero (- 273.15 ℃) can produce infrared. Modern physics calls it thermal ray. Medical infrared can be divided into two categories: near infrared and far infrared.
Infrared emission tube
There are three commonly used bands in the LED packaging industry: 850nm, 875nm and 940nm. There are also great differences in the products used according to the characteristics of the wavelength. The 850nm wavelength is mainly used for infrared monitoring equipment, the 875nm wavelength is mainly used for medical equipment, and the 940nm wavelength is mainly used for infrared control equipment. Eg: infrared remote control, photoelectric switch, photoelectric counting equipment, etc.
Function description
The polarity of the tube cannot be mistaken. Usually the longer pin is positive and the other pin is negative. If the pin length cannot be identified (for example, the pin has been cut short), it can be determined by measuring its positive and negative resistance. When the positive resistance is small, the pin connected to the black probe is positive.
By measuring the forward and reverse resistance of the LED, the performance of the LED can be inferred to a great extent. Take the R × 1K gear of the 500 multimeter as an example, if the measured positive resistance value is greater than 20K Ω, there is a suspicion of aging; if it is close to zero, it should be scrapped. If the reverse resistance is only thousands of ohm, or even close to zero, the tube will be broken; the larger the reverse resistance is, the smaller the leakage current is, the better the quality is.
Photosensitive receiver
It is a PN junction with photosensitive characteristics, which belongs to photosensitive triode, and has single conductivity, so it needs to add reverse voltage when it works. When there is no light, there is a small saturated reverse leakage current (dark current). At this time, the phototube does not conduct. When the light is illuminated, the saturation reverse leakage current increases immediately, forming photocurrent, which increases with the change of incident light intensity in a certain range.
Infrared receiving tube
The function is similar to the photosensitive receiving tube but not interfered by visible light. It belongs to photosensitive diode and only reacts to infrared ray.
Infrared receiving head
It is the function of amplifying signal on the basis of infrared receiving tube, similar to the amplification effect of triode.
The judgment method of infrared tube
People are used to call the infrared emitting tube and the infrared receiving tube infrared antitube. The shape of the IR pair is similar to that of the ordinary round led. It is difficult to distinguish the transmitting tube from the receiving tube for the first contact.
1) The rxlk resistance block of 500 type or other type pointer type three-way meter can be used for measurement and identification with three-way meter, and the pole to pole resistance of infrared tube can be measured to distinguish infrared tube.
Criterion 1: under the condition that the end of the infrared counter tube is not exposed to light, when the probe is changed down for measurement, the positive resistance of the emitter tube is small and the reverse resistance is large, and when the black probe is connected to the positive pole (long pin), the one with small resistance (1k-20k) is the emitter tube. Both the positive and negative resistances are very large.
Criterion 2: when the black probe is connected to the negative pole (short pin), the transmitter tube has a large resistance, and when the pointer of the three meter changes with the light intensity, the receiver tube has a swinging pointer.
Note: (1) measure the positive resistance when the black probe is connected to the positive electrode and the red probe is connected to the negative electrode. (2) High resistance means that the pointer of the three meter is basically fixed.
2) Power on test method discrimination
Connect a LED and a resistance in series with the pair to be tested, as shown in Figure 2. The resistance in the figure acts as current limiting, and the resistance value is 220 Ω - 510 Ω. LED is used to display the working state of the infrared tube. Use the remote control (TV remote control, etc.) to press any key of the remote control on the tested tube. When the LED is on, the tested tube is an infrared receiving tube. If it's not bright, it's an infrared emitter.
By measuring the working voltage and current of the infrared light-emitting diode on the transmitter circuit, it is easy to determine how well it works. When measuring the working voltage at both ends of the tube, it is usually zero under static state (i.e. when there is no key pressed), while it will jump to a smaller voltage value under dynamic state (i.e. when a key is pressed). Due to the different coding mode of the remote control system, the structure of the driving circuit and the working power supply voltage, the voltage value is usually between 0.07-0.4v, and the probe should tremble slightly. When the digital multimeter is used for measurement, the measured value will generally be higher than that of the pointer multimeter, usually between 0.1 and 0.8V. If the meter needle shakes in static state and does not shake in dynamic state, shakes in static state and dynamic state, does not shake in static state and dynamic state, and there is no obvious difference between dynamic voltage and static voltage, it can be judged that the operation of the infrared light-emitting diode is abnormal. If the driving amplifier circuit is normal, the infrared light-emitting diode is mostly damaged.
The infrared light-emitting diode shall be kept clean and in good condition, especially the spherical emitting part at the front end shall be free of dirt and other pollutants, and shall not be damaged by friction. Otherwise, the infrared light emitted from the tube core will produce reflection and scattering phenomenon, which will directly affect the transmission of the infrared light. The light one may reduce the sensitivity of the remote control, reduce the control distance, and the heavy one may produce Life failure, even remote control failure.
The parameters of the infrared light-emitting diode shall not exceed the limit value in the process of operation. Therefore, the model and parameters of the original tube shall be paid attention to when selecting the replacement type, and can not be replaced at will. In addition, the current limiting resistance of the LED cannot be changed arbitrarily. Because of the wide range of infrared wavelength, the infrared light-emitting diode must be paired with the infrared receiving diode, otherwise it will affect the sensitivity of remote control and even cause out of control. Therefore, it is necessary to pay attention to the wavelength parameters of the radiated infrared signal when selecting the substitute.
The hardness of the infrared light-emitting diode packaging material is low, and its high temperature resistance is worse. To avoid damage, the solder joint should be away from the root of the pin in the daytime, the welding temperature should not be too high, and the welding time should not be too long. It is better to clamp the root of the pin with metal tweezers to help heat dissipation. The pin bending switch shall be finalized before welding, during which neither the pipe body nor the pin shall be stressed.
Infrared receiving head
Using small design, inner shielding module package, can do infrared decoding experiment, infrared remote control and so on. Cooperate with remote controller to complete remote decoding and infrared remote control experiment. It is widely used in infrared remote control system as receiving element
1. Audio visual equipment (such as VCD, DVD, DVB, TV, etc.)
2. Household equipment (such as air conditioners, fans, lights, etc.)
3. Infrared remote control (such as toys, etc.)
Metal package infrared receiving tube is suitable for all kinds of photoelectric conversion automatic control instruments, sensors and signal light sources of all kinds of photoelectric detectors. According to the driving mode, stable light, pulse light and slow change light can be obtained. It is commonly used in control, alarm and other aspects; It adopts the structure of reflection function, strong optical power, low driving voltage, easy to match with transistor circuit, strong structure, shock resistance, high reliability, metal glass packaging device, good wear resistance and temperature resistance.
The receiver has only three external pins: out, GND, VCC and SCM Interface, as shown in the figure.
① The output of the pulse signal is connected directly to the IO interface of the single chip microcomputer.
② GND ground wire of grounding system (0V);
③ VCC is connected to the positive pole of the system (+ 5V);
