Today in radio electronics there are a wide variety of products used to create high-quality and effective lighting. One such product is an infrared diode type.

To use it to create backlighting, you need to know not only where they are used, but also their features. This article will help you understand this issue.

Features of diodes operating in the infrared range

Infrared LEDs (abbreviated as IR diodes) are semiconductor elements of electronic circuits, which, when current passes through them, emit light in the infrared range.

Note! Infrared radiation is invisible to the human eye. This radiation can only be detected by using stationary video cameras or mobile phone video cameras. This is one way to check whether a diode operates in the infrared spectrum.

High-power LEDs (for example, laser type) in the infrared spectral range are produced on the basis of quantum-sized heterostructures. An FP type laser is used here. As a result, the LED power starts at 10 mV, and the limiting threshold is 1000 mV. Housings for this type of product are suitable for both 3-pin and HHL types. As a result, the radiation appears in the spectrum from 1300 to 1550 nm.

IR Diode Structure

As a result of this structure, a high-power laser diode serves as an excellent source of radiation, due to which it is often used in fiber-optic information transmission systems, as well as in many other areas, which will be discussed below.
The infrared laser diode type is a source of powerful and concentrated laser radiation. In its work, the laser principle of operation is used.
Power diodes (laser type) have the following technical characteristics:

Note! Due to the fact that the product emits light in the infrared range, such familiar characteristics as illumination, power of emitted light flux, etc. don't fit here.

Graphic display of solid angle in 1 sr

• such LEDs are capable of generating waves in the range of 0.74-2000 microns. This range serves as the limit when radiation and light have a conventional division;
• power of generated radiation. This parameter reflects the amount of energy per unit time. This power is additionally tied to the dimensions of the emitter. This parameter is measured in W per unit of available area;
• intensity of the emitted flux within the frame of the volumetric angle segment. This is a rather conditional characteristic. It is due to the fact that, with the help of optical systems, the radiation emitted by the diode is collected and then directed in the required direction. This parameter is measured in watts per steradian (W/sr).

In some situations, when there is no need for a constant flow of energy, but pulsed signals are sufficient, the above-described structure and characteristics make it possible to increase the power of energy emitted by a radio circuit element several times.

Note! Sometimes in the characteristics of infrared diodes, indicators for continuous and pulsed operating modes are distinguished.

How to check functionality

Checking the IR diode

When working with this element of the electrical circuit, you need to know how to check its operation. So, as already mentioned, you can visually check the presence of this radiation using video cameras. Here you can evaluate performance using conventional mobile phone video cameras.
Note! Using video cameras is the easiest way to check.

This IR element in the remote control is easy to check; you just need to point it at the TV and press the button. If the system is working properly, the diode will flash and the TV will turn on.
But you can empirically check the performance of such an LED using special equipment. A tester is suitable for these purposes. To test an LED, the tester should be connected to its terminals and set to the mOm measurement limit. After that, we look at it through a camera, for example through a mobile phone. If a beam of light is visible on the screen, then everything is in order. That's the whole test.

Scope of application of IR diodes

At this point in time, infrared LEDs are used in the following areas:

• in medicine. Such elements of radio circuits serve as a high-quality and effective source for creating directional illumination for a variety of medical equipment;
• in security systems;
• in an information transmission system using fiber optic cables. Due to their special structure, these products are capable of working with multimode and single-mode optical fiber;
• research and scientific spheres. Such products are in demand in the processes of pumping solid-state lasers during scientific research, as well as illumination;
• military industry. Here they have the same wide application as illumination as in the medical field.

In addition, such diodes are found in various equipment:

• devices for remote control of equipment;

IR diode in the remote control

• various control and measuring optical instruments;
• wireless communication lines;
• switching optocoupler devices.

As you can see, the scope of application of this product is impressive. Therefore, you can purchase such diode components for your home laboratory without any problems; they are sold in abundance on the market and in specialized stores.

Conclusion

Today there is no doubt about the effectiveness of high-power infrared LEDs. This is confirmed by the fact that such elements of electrical systems have a wide range of applications. Due to their structure, IR LEDs are distinguished by impeccable performance characteristics and high-quality work.

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At the end of the USSR, domestic semiconductor TVs of the USCT series appeared and were very popular. Some of them are still in service. TVs with a screen size of 51 cm diagonally were especially durable (the kinescope was very reliable). Of course, they no longer meet modern requirements at all, but as a “dacha option” they are still quite suitable.

How to make a simple IR remote control for TV

Somehow, out of nothing to do, a desire arose to improve the old, already “dacha” “Raduga-51ТЦ315”, adding a remote control system to it. Now it is impossible to purchase a “native” module, so it was decided to make a simplified single-command system that allows at least switching programs “in a ring”. Microcontrollers and special microcircuits were immediately rejected due to unprofitability, and the system was made from what was available.

Namely, integrated timer 555, IR LED LD271, integrated photodetector TSOP4838, counter K561IE9 and plus some other little things. The diagram of the IR control panel is shown on the website. It is a pulse generator with a frequency of 38 kHz, at the output of which an infrared LED is switched on. The generator is built on the basis of the “555” microcircuit, the so-called “integrated timer”. The generation frequency depends on the C1-R1 circuit; when setting up, by selecting resistor R1, you need to set the frequency at the output of the microcircuit (pin 3) to 38 kHz.

Rectangular pulses with a frequency of 38 kHz are supplied to the base of transistor VT1 through resistor R2. Diodes VD1 and VD2 together with resistor R3 form a current control circuit through the IR LED HL1. With increased current, the voltage on R3 increases, and the voltage on the emitter VT1 increases accordingly. And when the voltage at the emitter approaches the drop voltage across the diodes VD1 and VD2, the voltage at the base of VT1 decreases relative to the emitter, and the transistor closes.

Scheme of the receiving unit using IR radiation

Pulses of IR light, following with a frequency of 38 kHz, are emitted by the HL1 infrared LED. Control by one button S1, which supplies power to the remote control circuit. While the button is pressed by the remote control, infrared pulses are emitted. The circuit diagram of the receiving unit is shown in Figure 2. It is installed inside the TV, it is supplied with + 12V power from the TV’s power supply, and the cathodes of the VD2-VD9 diodes are connected to the contacts of the buttons of the USU-1-10 program selection module. IR pulses emitted by the remote control are received by an integrated photodetector HF1 type TSOP4838.

This photodetector is widely used in remote control systems for various household electronic equipment. When a signal is received, there is a logical zero at its pin 1, and a logical one when there is no received signal. Thus, when the remote control button is pressed, its output is zero, and when not pressed, its output is one. TSOP4838 should be powered with a voltage of 4.5-5.5V. and no more. But, to control the TV program selection module, you need to apply 12V voltage to the buttons of the transistor 8-phase trigger. Therefore, a voltage of 12V is supplied to the D1 chip, and a voltage of 4.7-5V is supplied to the photodetector HF1 through a parametric stabilizer on the zener diode VD10 and resistor R4.

Transistor VT1 serves as a cascade matching the levels of logical units. In doing so, it inverts the logic levels. The voltage from the collector VT1 through the circuit R3-C2 is supplied to the counting input of the counter D1, designed to receive positive pulses. The R3-C2 circuit is used to suppress errors from bouncing contacts of the S1 button on the control panel. Counter D1 K561IE9 is a three-digit binary counter, with a decimal decoder circuit at the output.

It can be in one of eight states from 0 to 7, while a logical one is present at only one output corresponding to its state. The remaining outputs are zeros. Each time you press or release the remote control button, the counter moves one state up, and the logical one of its outputs switches. If the countdown started from zero, then after eight presses of the button, on the ninth, the counter will return to the zero position. And then, the process of switching the logical unit along its outputs will be repeated. The LD271 IR LED can be replaced with any IR LED. applicable for remote controls for household appliances. The TSOP4838 photodetector can be replaced with any complete or functional analogue.

The K561IE9 chip can be replaced with a K176IE9 or a foreign analogue. You can use the K561IE8 (K176IE8) chip, and there will be 10 control outputs. To limit them to 8, you need to connect output number “8” to input “R” (in this case, input “R” should not be connected to a common negative, as is shown in the diagram). 1N4148 diodes can be replaced with any analogues, for example. KD521, KD522. The remote control is powered by Krona. Placed in a toothbrush case. Installation - volumetric on the terminals of the A1 chip.

The receiver circuit is also assembled using three-dimensional installation and glued with BF-4 glue to the wooden body of the TV from the inside. For the eye of the photodetector, I used the hole for the connector for connecting headphones (the hole in the TV was empty, closed with a plug, there was no connector). By selecting R1 (Fig. 1), you need to adjust the remote control to the frequency of the photodetector. This can be seen from the longest reception range. If you are interested in the circuit, but there is no old “Rainbow”, it can also be used to switch something more modern. Transistor switches, with electromagnetic relays on collectors or LEDs of powerful optocouplers can be connected to the outputs of the D1 microcircuit through resistors.

I. Ivanov

You can check the operation of the remote control in the absence of a TV using an infrared photodiode (PD). For example, the domestic FD-8K would be suitable. The PD leads are connected to the ground and signal probes of the oscilloscope. The remote control is placed coaxially with the FD close to its window. Press any of the buttons on the remote control. In this case, a PWM signal with an amplitude of 0.2...0.5 V should appear on the oscilloscope screen.

The circuits of most television remote controls are the same and include:
- a command generator microcircuit with a quartz resonator;
- an amplifier consisting of one or two transistors;
- LED (or two);
- keyboard and contact field.

In addition, some remote controls have an indicator LED that registers the command.

Let's consider possible malfunctions of the remote control, methods for detecting and eliminating them.

1. No signal from the remote control

Check the condition of the batteries. If the supply voltage is less than 2.5 V, the batteries must be replaced. For voltages greater than 2.5 V, check the short circuit current Is with a multimeter. For serviceable elements it should be equal to 1...3 A. If Is
Then open the remote control. This operation requires certain skills and accuracy. The main task in this case is not to leave scratches on the remote control body and not to break the latches. To open the remote control, use a regular screwdriver with a thin blade (currently there are special screwdrivers on sale with a blade 10...20 mm wide and 0.5 mm thick with a short handle).

They begin to open the remote control from the side where the batteries are located, and first disconnect one side of the bottom cover to the entrance window, and then the other in the same way, after which the cover is easily removed.

Conduct an external inspection of the condition of the printed circuit board and keyboard contacts.

Traces of dried liquid on the contact field are removed using a cotton swab moistened with alcohol. Conductor breaks are eliminated by soldering jumpers made of thin wire.

Check for contact between the graphite jumpers and the printed conductors.

By closing any pair of contacts on the printed circuit board, use an oscilloscope to check the presence of a PWM signal at the cathode of the LED.

If there is no signal and the DC voltage is zero, check the continuity of the LED. A working LED should have a resistance in the forward direction of several tens of ohms, and in the reverse direction - several hundred kilo-ohms. A faulty LED must be replaced.

A fairly common defect is a break in the LED output as a result of mechanical impact, for example, after the remote control is dropped.

Check the passage of the PWM signal from the output of the microcircuit to the LED.

2. There is no signal at the output of the remote control chip

lack of supply voltage to the microcircuit;
malfunction of the quartz resonator;
the presence of two or more pairs of closed contacts on the printed circuit board;
breakage of conductors between the microcircuit and the contacts of the printed circuit board;
microcircuit malfunction.

First, check the supply voltage of the microcircuit: it must be at least 2.5 V.

The performance of the quartz resonator is checked by closing any of the pairs of contacts on the printed circuit board. If there is no generation, then most likely the microcircuit is faulty.

3. There is no signal from the remote control. There is a signal at the output of the microcircuit

Possible causes of the malfunction:
lack of amplifier supply voltage;
malfunction of amplifier elements;
LED malfunction.

Using an oscilloscope, check the presence of a signal at the cathode of the LED. If there is no signal here, check its passage from the output of the microcircuit to the LED.

The most common defects in this case are failure of the transistor in the output stage of the amplifier, violation of the soldering connections, and the terminals of the amplifier elements.

4. There is no signal from the remote control. The photodiode indicates the presence of a constant voltage level. Batteries drain quickly. The LED is constantly open and a significant current flows through it

Possible reasons:
breakdown of one of the amplifier transistors;
the presence of two or more pairs of closed keyboard contacts;
microcircuit malfunction.

The serviceability of the transistors and the presence of closed contacts are checked by dialing. The serviceability of the microcircuit is checked by replacement.

5. Some command is constantly sent from the remote control when the keyboard buttons are not pressed. Batteries drain quickly

Possible causes of the malfunction:
reducing the insulation resistance between the terminals of the microcircuit or the contacts of the printed circuit board;
reducing the insulation resistance between the graphite jumper and the printed conductor passing under it;
microcircuit malfunction.

Thoroughly wash the microcircuit terminals with alcohol, removing traces of rosin, dust, and dirt. On the printed circuit board, wipe the contacts with a cotton swab moistened with alcohol. Solder the corresponding pins of the microcircuit from the board. If after this commands from the remote control continue to arrive, the chip is changed. If the signal disappears, look for a current leak from the graphite jumper to the printed conductor. The conductor is cut off on both sides and a jumper made of insulated wire is installed (unsoldered) instead.

6. One or more remote control buttons do not work

Possible causes of the malfunction:
increasing the resistance of the keyboard's closing contacts;
crack on the board.

Use a multimeter to measure the resistance of the contacts. For working buttons it is 2...5 kOhm. If the resistance is more than 10 kOhm, the button is faulty. In this case, either change the entire rubber band or repair the contact. Special repair kits for remote controls are available for sale. They consist of contacts made of conductive rubber, which are glued to the faulty keyboard contacts with silicone glue included in the repair kit.

The presence of cracks is determined visually. Damaged printed conductors are restored using thin wire jumpers.

Most modern remote controls provide the ability to convert them into a service remote control. The essence of the modification is to install a new or rearrange an existing jumper on the printed circuit board, and the installation location on the board is indicated.

As an example, the figure shows the RM-836 remote control for SONY TVs with the top cover removed. After installing the jumper in pos. 1

The functionality of the image format change button changes.

Now, after pressing this button twice, the TV is switched from operating mode to service mode.

Repair of remote controls.

M.Kireev

After several years of operation, the functioning of remote controls for televisions and other equipment often malfunctions. This is possible for several reasons: violation of the integrity of the soldering of electronic components, oxidation of the spring contacts in the battery compartment, complete or partial abrasion of the conductive layer applied to the ends of the buttons (Fig. 1),

Which are the most commonly used.

To eliminate the last defect, a simple method is proposed that has been tested for several years and does not require large expenses. On the end of the button, cleaned and degreased, for example with alcohol, the functionality of which needs to be restored, apply one layer of quick-drying glue, for example, “Secunda”, and then stick on a piece of aluminum foil slightly larger than the area of ​​the end of the button. After the glue has hardened, the protruding foil is carefully crimped with tweezers (Fig. 2).

Practice has shown high reliability and trouble-free operation of remote controls repaired in this way.

If you have to repair remote controls frequently, you can make a device for monitoring their performance, assembled from available parts (Fig. 3).

The DA1 chip serves to amplify the signal coming from the infrared photodiode VD1 and generate a sequence of output pulses that goes to the divider DD1.1. When you press any button on a working remote control, the VD2 LED will blink at a frequency of several hertz. The device is conveniently mounted in a housing measuring 100 x 40 x 30 mm (Fig. 4).

The DA1 chip can be replaced with domestic analogues KR1054UI1, KR1054ХА3, KR1056UP1, KR1084UI1, taking into account the difference in pinouts.

Repair & Service

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Infrared remote controls have firmly taken their place in consumer electronics. Any equipment that is not equipped with this very convenient device includes televisions, stereo systems, microwave ovens, car CD/MP players, chandeliers and many many other things familiar to us.

Such a widespread use of remote controls could not help but affect their frequent breakdowns. Since it is sometimes difficult to purchase a new remote control needed for a specific device, they are sent in for repair.

How to quickly check the remote control?

The simplest and most effective method is to check remote controls using digital cameras. Nowadays, almost every cell phone has a digital camera.

Many laptops have a built-in webcam. For netbooks, a digital web camera is generally a mandatory attribute. Digital photo and video cameras are also suitable for testing remote controls. In general, any device that has even the simplest digital camera is suitable for testing the remote control.

To check the remote control, you only need to point the emitting infrared LED at the camera lens. On the digital display, when you press buttons on the remote control, periodic flashes of purple light will be visible. This indicates that the remote control is working properly.

The photo shows the flashes of an infrared LED captured by the camera of a Sony Ericsson K810i mobile phone.

If you don’t have devices with a digital camera at hand, you can use the following method.

Instead of an infrared LED, it is necessary to temporarily solder in a regular light-emitting diode. The LED can be of any color: red, green, yellow, white, in general, it doesn’t matter, the main thing is that the LED is 3 volts.

When you press the buttons on the remote control, a temporarily soldered ordinary LED will emit flashes of light. It should be noted that the brightness of the radiation will be low.

In the photo - a regular white LED, soldered in instead of an infrared one.

The remote control can be tested using an infrared photodiode and an oscilloscope.

In this case, an infrared photodiode is connected to the input of the oscilloscope. When the remote control is operating, pulses of short bursts will be visible on the oscilloscope screen. It is important that the photodiode is connected to the open input of the oscilloscope.

This is how simple and easy it is to check the functionality of any infrared remote control. To do this, it is not at all necessary to collect any sample circuits and clutter up the resulting overloaded workshop, because all the necessary tools are already at hand, especially a mobile phone with a camera

An infrared (IR) emitting diode is a semiconductor device whose operating spectrum is located in the near-infrared region: from 760 to 1400 nm. The term “IR LED” is often used on the Internet, although it does not emit light visible to the human eye. That is, within the framework of physical optics this term is incorrect, but in a broad sense the name is applicable. It is worth noting that during operation of some IR emitting diodes, a weak red glow can be observed, which is explained by the blurring of the spectral characteristics at the border with the visible range.

IR LEDs should not be confused with infrared laser diodes. The operating principle and technical parameters of these devices are very different.

Application area

Let’s take a closer look at what infrared LEDs are and where they are used. Many of us encounter them every day without knowing it. Of course, we are talking about remote controls (RC), one of the most important elements of which is the IR emitting diode. Due to its reliability and low cost, the method of transmitting a control signal using infrared radiation has become widespread in everyday life. These remote controls are mainly used to control the operation of televisions, air conditioners, and media players. When you press a button on the remote control, the IR LED emits a modulated (encrypted) signal, which is received and then recognized by a photodiode built into the body of the household appliance. In the security industry, video cameras with infrared illumination are very popular. Video surveillance, supplemented with IR illumination, allows you to organize round-the-clock monitoring of the protected facility, regardless of weather conditions. In this case, IR LEDs can be built into the video camera or installed in its working area in the form of a separate device - an infrared spotlight. The use of high-power IR LEDs in the floodlights allows for reliable control of the surrounding area.

Their scope of application is not limited to this. The use of IR emitting diodes in night vision devices (NVDs), where they perform the function of illumination, has proven to be very effective. With the help of such a device, a person can distinguish objects at a fairly large distance in the dark. Night vision devices are in demand in the military sphere, as well as for covert night surveillance.

Types of IR Emitting Diodes

The range of LEDs operating in the infrared spectrum includes dozens of items. Each individual specimen has certain characteristics. But in general, all IR semiconductor diodes can be divided according to the following criteria:

• radiation power or maximum forward current;
• purpose;
• form factor.

Low-current IR LEDs are designed to operate at currents of no more than 50 mA and are characterized by a radiation power of up to 100 mW. Imported samples are manufactured in an oval 3 and 5 mm housing, which exactly replicates the dimensions of a conventional two-terminal indicator LED. Lens color ranges from transparent (water clear) to translucent blue or yellow. Russian-made IR emitting diodes are still produced in miniature packages: 3L107A, AL118A. High-power devices are produced both in DIP housing and using SMD technology. For example, SFH4715S from Osram in an smd housing.

Specifications

In electrical diagrams, IR emitting diodes are designated in the same way as LEDs, with which they have much in common. Let's look at their main technical characteristics.

Operating wavelength– the main parameter of any LED, including infrared. The passport for the device indicates its value in nm, at which the highest radiation amplitude is achieved.

Since an IR LED cannot operate at only one wavelength, it is customary to indicate the width of the emission spectrum, which indicates a deviation from the declared wavelength (frequency). The narrower the radiation range, the more power is concentrated at the operating frequency.

Rated forward current– direct current, at which the declared radiation power is guaranteed. It is also the maximum permissible current.

Maximum pulse current– current that can be passed through the device with a fill factor of no more than 10%. Its value can be ten times higher than direct direct current.

Forward voltage– voltage drop across the device in the open state when the rated current flows. For IR diodes, its value does not exceed 2V and depends on the chemical composition of the crystal. For example, UPR AL118A=1.7V, UPR L-53F3BT=1.2V.

Reverse voltage– the maximum voltage of reverse polarity that can be applied to the p-n junction. There are instances with a reverse voltage of no more than 1V.

IR emitting diodes of the same series can be produced with different scattering angles, which is reflected in their markings. The need for similar devices with a narrow (15°) and wide (70°) radiation flux distribution angle is caused by their different scope of application.

In addition to the basic characteristics, there are a number of additional parameters that should be taken into account when designing circuits for operation in pulsed mode, as well as in environmental conditions other than normal. Before carrying out soldering work, you should familiarize yourself with the manufacturer’s recommendations on observing the temperature regime during soldering. You can find out about the permissible time and temperature intervals from the datasheet for the infrared LED.

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