Purpose, types and principle of operation of the lens for the LED

Cars admin26.02.2020

Due to high energy efficiency indicators, today ice elements are increasingly used as light sources for head optics for cars and other lamps. However, to display their 100% potential, a special focusing system is required. As a rule, LED lenses are used for this. Let's look at what they are, what their purpose is, what main types they exist, what material is used to make them, and also how to make them yourself.

Principle of operation

The principle of operation of lenses for flat and other forms of lamps with LEDs is based on the natural law of nature on the refraction of light waves at the boundary of two different media. In this case, it concerns the optics material (glass, plastic) and air. The refraction of a light flux significantly depends on the shape of the boundary through which it passes.

For example, thanks to a special lens with convex sides, the LED of a hand-held flashlight focuses a narrow beam within 12-15 degrees. Lighting characteristics also vary depending on the distance of the ice crystal to the interface between the media, as well as on the obstacle installed between them. In some automotive optics systems, this is used to switch from low beam to high beam and vice versa.

Important! To effectively illuminate extended areas, which, for example, is important when driving a car in the dark, the light flux must be given an oval shape in the horizontal direction. To do this, the lens must have a special complex design. Therefore, many manufacturers of car headlights, street lamps and floodlights produce ready-made optical kits with LEDs.

Charger for nickel-cadmium batteries

Now you need to build a charger for the flashlight. The main requirement is that the output voltage should not exceed 4.2 V.

If you plan to power the charger from any source of more than 6 volts, a simple circuit based on KR142EN12A is relevant; this is a very common microcircuit for regulated, stabilized power. Foreign analogue of LM317. Here is a diagram of the charger on this chip:

But this scheme did not fit into my idea - versatility and maximum convenience for charging. After all, for this device you will need to make a transformer with a rectifier or use a ready-made power supply. I decided to make it possible to charge the batteries from a mobile phone charger and a computer USB port. To implement it, you will need a more complicated circuit:

The field-effect transistor for this circuit can be taken from a faulty motherboard and other computer peripherals; I cut it off an old video card. There are plenty of such transistors on the motherboard near the processor and not only. To be sure of your choice, you need to enter the transistor number into the search and make sure from the datasheets that it is a field effect one with an N-channel.

I used the TL431 microcircuit as a zener diode; it is found in almost every mobile phone charger or other switching power supplies. The pins of this microcircuit must be connected as in the figure:

I assembled the circuit on a piece of PCB and provided a USB socket for connection. In addition to the circuit, I soldered one LED near the socket to indicate charging (that voltage is being supplied to the USB port).

A few explanations about the diagram

Since the charging circuit will always be connected to the battery, the VD2 diode is necessary so that the battery does not discharge through the stabilizer elements. By selecting R4, you need to achieve a voltage of 4.4 V at the specified test point, you need to measure with the battery disconnected, 0.2 volts is the reserve for drawdown. And in general, 4.4 V does not exceed the recommended voltage for three battery cells.

The charger circuit can be significantly simplified, but you will only have to charge from a 5 V source (the computer’s USB port meets this requirement); if the phone charger produces a higher voltage, it cannot be used. According to a simplified scheme, theoretically, batteries can be recharged; in practice, this is how batteries are charged in many factory products.

Purpose

If in conventional flashlights, where fluorescent light sources or incandescent lamps are used, a reflector (reflector) is used as a focusing system, then a different device is required for LED elements. The reason for this lies primarily in the structure and principle of operation of the ice source itself and its lighting characteristics. LEDs have a different directional pattern of lighting flux from standard lamps.

This is primarily due to the small size of the emitter - the semiconductor crystal, which gives them such specific technical characteristics as:

1. Point properties even at very short distances.
2. Small angle of light flux dispersion.

Therefore, in order to obtain the required light distribution curve in space (as with conventional light bulbs), it is necessary to resort to various kinds of technological tricks. One of them is the use of lenses for LEDs. First of all, these are car headlights, spotlights, street lamps and other powerful lamps. Indoor chandeliers, on the contrary, use diffusers to create comfortable, uniform lighting.

Note! Initially, the LED creates a normal flow of light with a gradual decrease in its strength as it moves away from its central axis. To give it a given shape, special lenses are used. They are superimposed on the ice crystal and belong to the category of secondary optics.

The simplest lanterns

Since flashlights are different, it makes sense to start with the simplest one - with a battery and an incandescent lamp, and also consider its possible malfunctions. The circuit diagram of such a device is elementary.

Diagram of a simple flashlight

In fact, there is nothing in it except a battery, a power button and a light bulb. And therefore there are no special problems with it. Here are a few possible minor troubles that may result in the failure of such a flashlight:

• Oxidation of any of the contacts. These could be the contacts of a switch, light bulb or battery. You just need to clean these circuit elements, and the device will work again.
• Burning out of an incandescent lamp - everything is simple here; replacing the light element will solve this problem.
• The batteries are completely discharged - replace the batteries with new ones (or charge them if they are rechargeable).
• Lack of contact or broken wire. If the flashlight is no longer new, then it makes sense to change all the wires. This is not at all difficult to do.

Types of lenses

Modern manufacturers classify lenses for LEDs according to two main criteria:

1. A type of ice element.
2. Light distribution models.

Among the secondary characteristics of optics are the number of LEDs, the symmetry of their location, as well as the transparency or dullness of the material. The most popular type of luminous flux distribution is round symmetrical. This can be a cascade of series-connected ice crystals with a small nominal value of 1-3-5 W.

Their light angle can vary within a fairly wide range - from several to one and a half hundred degrees. Some characteristic species have their own names. For example, lenses that focus the light beam to no more than 10 degrees are called spot lenses (“spot” means “spot”).

Important! Factories producing LEDs interact with manufacturers of lenses used for them. Therefore, when some go on sale, after a certain time you can find others.

So which flashlight should you choose?

Of course, flashlights can be different in voltage consumption (from 1.5 to 12 V), and with different switches (touch or mechanical), with an audible warning about low battery. This may be the original or its analogues. And it’s not always possible to determine what kind of device is in front of your eyes. After all, until it fails and repairs begin, you cannot see what kind of microcircuit or transistor is in it. It’s probably better to choose the one you like and solve possible problems as they arise.

Making a lens with your own hands

If it is not possible to buy a ready-made optical kit, then you can assemble it yourself. To do this you will need:

1. Light-emitting diode.
2. A magnifying glass of suitable diameter (for example, a magnifying glass).

To assemble the lantern, you need to fix the lens itself at some distance from the ice crystal. It is better to determine the size of this gap experimentally by first turning on the LED and placing a magnifying glass in front of it and pointing it at the surface (wall), moving it to determine the optimal focus and brightness.

You can secure the lens either by gluing it to the ice element, or by clamping it between the body and the protective glass of the flashlight, or by building a special holder for it, which is mounted with glue or bolts to the board. Not least important in this process is the alignment of the magnifying glass relative to the plane and the central perpendicular axis of the crystal. It needs to be installed as accurately as possible.

During installation, the lens should not become contaminated with grease stains from the fingers. Otherwise, the quality of lighting will be greatly reduced. When choosing a magnifying glass for a lamp with LEDs, you need to pay attention to the following parameters:

1. Angle of light flux formation.
2. Appearance, size and shape.
3. Degree of installation complexity.
4. Symmetry.
5. Optical characteristics.

Recommendation! Lenses produced specifically for LEDs have special holders that correspond to their lighting characteristics and greatly facilitate installation.

Homemade device powered by a AA battery: necessary materials

Making a powerful flashlight with your own hands is a difficult task, for which you first need to prepare all the necessary components. The list includes the following details:

• super bright LED;
• ferrite filter, the diameter (Ø) of which should be 10–15 mm;
• enamel wire Ø 0.1 and 0.25 mm;
• resistor;
• bipolar transistor npn structure (for example, KT315 or BC547C);
• AA battery.

The last element should be present in every home, so there should be no problems finding it, but the remaining components will have to be purchased. In addition, you will need a housing (for example, from an old unnecessary flashlight) or any base on which the parts will be attached.

Main conclusions

The lens for the LED is designed to focus the luminous flux of the lamp. This allows you to create directional lighting with specified characteristics. For example, ovally distributed in a horizontal plane, which is necessary to illuminate the road for a moving car or a spotlight.

Lamps of this type differ in:

1. I see an ice crystal.
2. Their number.
3. The symmetry of their location.
4. Type of luminous flux distribution.

Modern flashlights with LED lenses are capable of focusing light from a few to one and a half hundred degrees. To equip cars, bi-lenses are most often used - capable of forming low and high beams. Their main material is glass or polycarbonate. To make such an optical system with your own hands, you need to purchase a special or universal magnifying glass and fix it, observing the requirements of alignment, above the ice element at a certain distance in accordance with the specified parameters.

• Price: $2.42

• Go to the store

Greetings Muskovites! Not very long ago I ordered some good LEDs with a power of 10 W here (not an advertisement, since I saw them in a review from the respected dia). I liked the LEDs - for their price they turned out to be really high quality, all copies have an almost perfectly uniform glow at low current. But that's not the point. I screwed them to the radiator, driver and powered them up. I liked everything, but I wanted a little more. In terms of power. Well, I wanted to curb the luminous flux a little, so to speak))) The idea arose to take a more powerful LED and make it into something like a garage spotlight. I started rummaging through Aliexpress and came across lenses for a homemade spotlight (or maybe something else). I decided to order two sets at once.

Assembly diagram

Before making a lantern, you need to make a transformer from a ferrite filter and enamel wire. The method for implementing this device includes the following steps:

1. Wind 45 turns of enamel wire with a diameter of 0.25 mm onto the ferrite filter. The result is a secondary winding, to which you will later need to connect an LED.
2. Make the primary winding in this way: wind an enameled wire with a diameter of 0.1 mm 30 times, and then direct it to the base of the transistor.

When the described work on making a homemade transformer is completed, then you need to start selecting a resistor. The resistance of the specified element used in the circuit should be about 2 kOhm, since only in this case will the device operate without failures. However, you first need to test the circuit, and to do this you need to replace the resistor with a similar one, but with an adjustable resistance. After connecting the flashlight to a new battery, you need to adjust the resistance on the variable resistor so that the LED passes a current of 25 mA. The next step is to measure the obtained value and install an element with the required rating.

An electrical circuit is needed to power the LED from a battery, since the operating voltage of super-bright diodes is at least 2.5 V. But in the end, you will be able to make a powerful flashlight that will work for quite a long time. The circuit below is a regular blocking generator, so the likelihood of making an error is minimized.

Purpose

The luminous intensity curve (LIC) displays the spatial distribution of luminous flux. For different applications, luminaires must have their own type of luminous intensity curve. The main KSS are shown in the figure.

LEDs, unlike other light sources, such as fluorescent lamps, have quite small physical dimensions. Therefore, even at short distances they can be considered point sources. In addition, LEDs are characterized by a small dispersion angle of the light flux, less than 120 o. Therefore, without technical tricks, it is quite difficult to obtain the required luminous intensity curve using LED.

Engineers find different technical solutions for different problems. For example, in LED lamps, the spatial arrangement of LEDs and frosted bulbs are used to obtain the required luminous intensity curve. Ceiling lamps use prismatic or frosted polycarbonate diffusers.

In more complex devices, such as street lamps, spotlights, portable lamps, and automotive LED optics, lenses for LEDs or lenses in combination with reflectors are used. Experts classify all these and other optical devices as “secondary optics”.

Board parameters

• Input voltage from Micro USB: 5V
• Charging cut-off voltage: 4.2V ± 1%
• Maximum charging current: 1000mA
• Battery over-discharge overvoltage protection: 2.5V
• Installed overcurrent protection current: 3A
• Board size: 2.6*1.7CM

In fact, this is a separate board that is used in a power bank, and if you buy an additional USB output, you can charge your phone

Let's start remaking

Disassembled view of the flashlight and the first stage of assembly
Now, about the conversion of the flashlight itself to use a battery instead of batteries, most flashlights use 3 AA 1.5 V in size, comparable to a mobile battery, and fits quite well in the main body, you just have to expand the seat. After simple manipulations, having unscrewed or cut out all the excess, we mount all the parts in place using hot-melt adhesive.

Scheme for converting an LED flashlight Solder all the parts in place using a heat gun If necessary, you can increase the capacity by connecting 2 batteries We get a modernized headlamp with a mini USB input

In conclusion: the LED flashlight worked actively for 3 nights on old telephone batteries without recharging. Perhaps it would have been enough for more, I didn’t test it before the cutoff. Lithium batteries do not like to be completely discharged. Overall, very pleased at the cost of 140 rubles. The only thing is that it is very bright, which is not always necessary. I was pleased with the presence of charge indicators on the board. When charging via USB, it glows red when the battery is charged blue.

Almost any flashlight can be converted in this way, the only question is the size of the battery. For example, iPhone batteries are not very practical, and if you tear off the contacts from the connection board carelessly, they will not be soldered.

Do not use lithium batteries if they are swollen - it is unsafe!

It happens that the protection on the board is triggered, and you need to revive it, in this case, apply voltage from the power supply or power bank. If the phone batteries are very old, then the protection of the headlamp will naturally work faster and it will go out. Although batteries from an old Nokia (more than 4 years old) work properly.

Save money when purchasing and, accordingly, buy cheaper (this is when % from the purchase accumulates). So you just install a browser extension and the money gradually accumulates on its own.

Materials for manufacturing and methods of fastening

Most manufacturers use clear polycarbonate to produce lenses. This material has excellent optical properties. Due to low losses due to internal absorption and reflection of light, the efficiency of optical systems based on polycarbonate is 90% or more.

The material works well in a wide temperature range, is not subject to rapid aging, is lightweight, and has sufficient strength. An important advantage of polycarbonate over other materials is its manufacturability, which allows the production of cheap and high-quality lenses on an industrial scale.

Of course, traditional glass is also used for LED lenses. Most often borosilicate varieties. Glass lenses have greater hardness and are therefore more scratch resistant.

Depending on the type of housing, lenses can be held on the LED using friction (yes, yes, that’s friction - there is such a technology), attached using special fittings, or glued to LED radiators or printed circuit boards. For example, 5450 LEDs with clip lenses are often used for decorative lighting. At the same time, it is held on the LED by friction.

Refinement of Chinese lanterns

Sometimes it happens that a purchased flashlight with a battery (which appears to be of good quality) completely fails. And it is not necessarily the buyer’s fault for improper operation, although this also occurs. More often, this is a mistake when assembling a Chinese lantern in pursuit of quantity at the expense of quality.

Of course, in this case it will have to be remade, modernized somehow, because the money has been spent. Now you need to understand how to do this and whether it is possible to compete with the Chinese manufacturer and repair such a device yourself.

Considering the most common option, in which when the device is plugged in, the charging indicator lights up, but the flashlight does not charge and does not work, you can notice this.

A common mistake by the manufacturer is that the charge indicator (LED) is connected in parallel with the battery, which should never be allowed. At the same time, the buyer turns on the flashlight, and seeing that it is not lit, again supplies power to the charge. As a result, all LEDs burn out at once.

The fact is that not all manufacturers indicate that such devices cannot be charged with the LEDs turned on, since it will be impossible to repair them, all that remains is to replace them.

So, the modernization task is to connect the charge indicator in series with the battery.

Modernization of Chinese marriage

As can be seen from the diagram, this problem is completely solvable.

But if the Chinese installed a 0118 resistor in their product, then the LEDs will have to be changed constantly, because the current supplied to them will be very high, and no matter what light elements are installed, they cannot withstand the load.

LEDs with lenses for cars

Many automakers, when developing new car models, are actively switching to LED lighting technology. This approach is completely justified. After all, a 10 W LED headlight will shine like a 100 W one. Naturally, along with the use of LEDs, the secondary optics of cars have also changed. LEDs in the headlights are used in conjunction with specially designed lenses that create light intensity curves that meet all traffic regulations.

Unfortunately, it is very difficult to install LEDs in the headlights of old cars instead of incandescent lamps. However, manufacturers find a way out. On the market you can find LED car low beam lamps. Even more offers for tuning lovers. There are a variety of LED headlights available with lenses that can be mounted on the grille or bumper. The already mentioned combination of LED 5450 with clip lenses is often used for decorative lighting of various car elements.

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Comments 10

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Very great idea and timely

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Never better!

Just what you need. Interesting topic, I will participate. I know that together we can come to the right answer.

Wonderful, this is a valuable phrase

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