Infrared receiver (also called infrared receiver module, IRM) is an integrated infrared receiver PD diode.
IC module for amplifying, filtering and comparator output. We don't do the receiving and amplifying circuit any more, so the infrared receiver simplifies the circuit.
The commonly used infrared receiver has three pins, namely, power supply positive VDD, power supply negative GND and data output out. Different types of receiver pins are arranged differently, and different shapes of receiver pins are also different.
The main parameters of the infrared receiver are as follows:
Working voltage: 2.7~4.5V Working current: 1.7~2.7mA Receiving frequency: 37.9kHz Peak wavelength: 940nm Static output: high level.
Output low level: ≤0.4V Output high level: close to working voltage.
2. The principle of infrared receiver
The infrared receiving tube of the receiving circuit is a photosensitive diode. When in use, it needs reverse bias to work normally and obtain high sensitivity. Generally, there are two kinds of infrared receiving diodes: round and square. Due to the low emission power of infrared light emitting diode and the weak signal received by infrared receiving diode, a high gain amplifier circuit should be added at the receiving end. But at present, no matter amateur production or regular products, most of them use finished integrated receivers. Integrated infrared receiver is a module that integrates infrared receiving, amplification, filtering and comparator output, and its performance is stable and reliable. Therefore, with the integrated receiver, people no longer make receiving and amplifying circuits, which is not only simple, but also greatly improves the reliability.
The infrared receiver includes two chips, one is PD (infrared receiver tube) and the other is IC. Among them, PD receives the optical signal from the transmitting tube (modulated) and converts the optical signal into an electrical signal, that is, photoelectric conversion, which is often used in optical receivers. PD chip is a typical PIN photodiode. The electrical signal received and converted by PD is amplified by IC, automatically controlled by gain, filtered, demodulated and shaped by waveform, and the comparator output is recognized and recovered by subsequent circuits. The above is the receiving process of infrared receiver.
3. What are the infrared receivers?
The photosensitive tube and the intermediary IC package are integrated to form an integrated infrared receiver.
The internal circuit includes infrared photodiode, amplifier, limiter, band-pass filter, integrating circuit, comparator and so on. The infrared photodiode monitors the infrared signal, and then sends the signal to the amplifier and limiter. The limiter controls the pulse amplitude at a certain level, regardless of the distance between the infrared transmitter and receiver.
Its main functions include amplification, frequency selection and demodulation, and it is required to modulate the input signal. After receiving, amplifying and demodulating, the original signal will be directly output at the output end.
Thereby simplifying the circuit! It has good sensitivity and anti-interference, and can be said to be an ideal device for receiving infrared signals.
4. How to use the first three needles of the infrared receiver?
1. generally, an infrared receiver has three pins, namely grounding, power supply and signal output. Different types of infrared receivers have different pin arrangements. The author uses resistance method to judge the pin of infrared receiver, which is simple and quick.
2. Use pointer multimeter (digital table is not applicable) to block R* 1k (or R* 100). First, measure and determine the grounding pin. Generally, the grounding pin is connected to the shielding shell, and the remaining two pins are assumed to be A and B..
3. Then put the black stylus on the grounding pin, and measure the resistance of pin A or pin B with the red stylus, and the readings are about 6kΩ and 8kΩ respectively (some receivers differ by about1kΩ); Replace the stylus, the red stylus is grounded, and the black stylus measures pins A and B, and the readings are about 20kΩ and 40kΩ respectively.
4. The pin A with relatively small resistance during the secondary measurement is the power supply pin, and the pin B with relatively large resistance is the signal output pin. However, using different multimeters and measuring different types of receiving heads, the measured resistance is different.
5. But the general conclusion is that the resistance value of the power supply pin to the ground is smaller than that of the signal pin to the ground regardless of the positive or negative direction.
Identification method of infrared receiver pin;
1. Prepare a 5V power supply first, because the normal working voltage of the three-terminal infrared receiver is 5V (it can also be replaced by a 3V power supply consisting of two batteries). Connect any foot of the three-terminal infrared receiver to be tested to the positive pole of the power supply, connect the black contact pin of the multimeter to the negative pole of the power supply, and connect the red contact pin to the other two feet of the infrared receiver, and measure its static current (the multimeter is equipped with a current block).
2. If the measured current reaches several tens of mA, the pin connection is wrong and should be disconnected immediately to avoid damage. Only when the measurement result is less than 3mA (the static current of various types of receiving heads is different) is the power terminal of the receiving head connected correctly, and these two pins are the positive and negative pins of the power supply.
3. Connect the positive and negative poles of the receiver to the power supply, connect the black probe of the multimeter to the negative pole of the power supply, and connect the red probe to another pin that is not connected to the power supply. If the voltage is close to the supply voltage, this pin is the output pin.
4. Aim any type of infrared remote controller at the receiving head, and let the remote controller emit a signal. If the voltage fluctuation of the output pin drops, it means that the pin has output the received data signal, which proves that the three pins are arranged correctly, and the receiving head is in good condition and can work normally.
5. What is the principle of infrared receiver?
The typical circuit of infrared signal transceiver system is shown in figure 1. The infrared receiver circuit is usually integrated into a component by the manufacturer to become an integrated infrared receiver.
The internal circuit includes infrared monitoring diode, amplifier, limiter, band-pass filter, integrating circuit, comparator and so on. The infrared monitoring diode monitors the infrared signal, and then sends the signal to the amplifier and limiter. The limiter controls the pulse amplitude at a certain level, regardless of the distance between the infrared transmitter and receiver. Exchange; connect
The signal enters the band-pass filter, which can pass the load wave from 30khz to 60khz, enter the comparator through the demodulation circuit and the integration circuit, and the comparator outputs.
High and low levels, restore the signal waveform of the transmitter. Note that the high level and low level of the output are opposite to the phase of the transmitter to improve the sensitivity of reception. There are many kinds of infrared receivers, and the definition of pin is different. Generally, there are three pins, power supply pin, grounding pin and signal output pin. According to transmitter modulation
For different carriers, the receiver with corresponding demodulation frequency should be selected. The gain of the internal amplifier of infrared receiver is very large, which is easy to cause interference, so the VCC of the receiver is very low.
The (voltage) PIN and the GND (ground) pin must be filtered.
Wave capacitance is generally 47uf ceramic capacitance (note: adding capacitance to 100uf or 20UF capacitance will shorten the receiving distance of the receiver). In addition, a 10K ohm pull-up resistor is connected in series between VCC (voltage) pin and Vout (output) to pull up when the voltage is unstable. The infrared transmitter can be customized by the remote controller manufacturer or generated by PWM of single chip microcomputer. For home remote control, it is recommended to use PWM which can generate 37.9 1KHz infrared emission tube (L5IR4-45), and the PWM duty ratio is set to 1/3. The transmission waveform can be generated by simply interrupting PWM at a fixed time.
We know that the visible light that human eyes can see is arranged from long to short wavelength, which is red, orange, yellow, green, cyan, blue and purple in turn. The wavelength range of red light is 0.62 ~ 0.76 micron; The wavelength range of violet light is 0.38 ~ 0.46 μ m. The light shorter than violet light is called ultraviolet light, and the light longer than red light is called infrared light. Infrared remote control uses the near infrared ray with the wavelength of 0.76 ~ 1.5μ m to emit control signals. ..
6. How does the infrared ray received by the infrared receiver behave?
Receiving principle: the infrared receiving circuit is usually integrated into a component by the manufacturer and becomes an integrated infrared receiving head.
The internal circuit includes infrared monitoring diode, amplifier, limiter, band-pass filter, integrating circuit, comparator and so on. The infrared monitoring diode monitors the infrared signal and then sends the signal to the amplifier and limiter. The limiter controls the pulse amplitude to a certain level regardless of the distance between the infrared transmitter and the receiver.
The AC signal enters the band-pass filter, which can pass the load wave from 30khz to 60khz and enter the comparator through the demodulation circuit and the integration circuit, and the comparator outputs high and low levels to restore the signal waveform at the transmitter end. Note that the high level and low level of the output are opposite to the phase of the transmitter to improve the sensitivity of reception.
So there should be no difference between open circuit and open circuit, only high and low.