DIY floodlight: design and principle of operation, choice of LEDs

External lighting in the dark is not only an important component of the comfort of various households, but also a necessary element of the security system. For the organization of outdoor lighting, floodlights are most often used, illuminating large areas and participating in the illumination of structures. Trading platforms offer a wide range of such products, but it will not be difficult to make an LED floodlight with your own hands.

Scope and device

The word "spotlight" was borrowed from the Latin language. Literally projectus means thrown forward. This concept refers to a device that emits light by redistributing and focusing the visible energy of a radiation source located inside it. The first prototype of such a device was developed by the Italian inventor Leonardo da Vinci, and for the first time it was created by the Russian mechanic-inventor Ivan Petrovich Kulibin.

The devices in question were originally used for installation on lighthouses., protected areas and in the film industry. They used a high-power incandescent lamp as a light source. The designs were distinguished by: large dimensions, low efficiency, increased heating.

With the development of semiconductor devices and the advent of high-power LEDs, a new era of floodlighting has begun. Due to the unpretentious design and economical use of energy, they began to be used not only in industrial and municipal facilities, but also in private households. Today they can be found on the facades of various residential and administrative buildings., tunnels, bridges. They illuminate monuments, banners, walkways, entrances and exits.

Device design

By its design, an LED floodlight is not a complex device. It can use either one powerful light-emitting diode (LED), or a group of them. To fix the device on various surfaces, a bracket is used, which in most cases is an integral part of the device.

The following main elements can be distinguished that make up the design of an LED floodlight:

• frame;
• light emission system;
• driver.

During operation of the device, in addition to the emission of light quanta, thermal energy is also released. Therefore, to protect the emitter and control elements of the searchlight, the body of the product is made of heat-conducting lightweight material. Basically, the cases are made of aluminum and duralumin, but for low-power devices it can also be made of plastic.

The light module is manufactured on the basis of COB (chip-on-board) or a matrix of SMD LEDs. The first type is the most common, as it was specially designed to create directional light, while the second, according to manufacturers, has a longer duration work.

The essence of COB technology is the use of a ceramic substrate on which frameless emitting crystals are placed. A phosphor layer is applied on top of them. This approach during production allows you to reduce the cost of the product and obtain a uniform glow, in which individual points of the crystals are practically invisible.

The power of the COB matrix can reach one hundred watts, and a well-executed heat sink allows achieving a practical light output of 100-150 lumens per watt. The service life of such a matrix, according to manufacturers, is about 30 thousand hours of operation. COB matrix technology is young, it appeared only in 2010 and continues to develop at a rapid pace.

SMD-matrices are a set of LEDs placed on an aluminum substrate. Usually, the power of one such element does not exceed two watts. The large number of LEDs located close to each other allows an average illumination of 110 lumens per watt. Their declared service life reaches 50 thousand hours. A feature of floodlights with SMD-matrix in comparison with single-matrix is ​​a higher luminous flux. This is due to the fact that LED chips with a ratio of more than 1 W per 0.9 lm are not used in single-matrix floodlights.

Operating principle

The work of the searchlight is based on the property of the p-n junction to emit light in the visible spectrum to the human eye. When a voltage is applied to a radioelement, charge carriers pass through the contact zone of two materials with different conductivity inside it. As a result, the charges collide, and a process arises, accompanied by the emission of light quanta.

The main parameter of the emitter is its operating current. That is, this is its strength at which the recombination process takes place. The temperature mode of the device depends on its value. High heating of the radioelement leads to its degradation and failure. Therefore, it is important to limit the amount of current supplied to the light device, in other words, the supply voltage. For this, an electronic board is used - a driver.

When the projector is switched on to a 220 volt alternating network, the voltage through the contact terminals is supplied to the device driver, in which it is rectified and reduced to the desired value. Then, from it, the signal gets to the light source. Focusing of the radiation flux is carried out by a Fresnel lens or a reflector. To prevent moisture and dust from getting inside the module, the case is treated with silicone sealants. Cooling of radioelements occurs naturally due to the holes and the design of the heat sink.

Characteristics of floodlights

The advantages of LED floodlights are their ease of installation, absence of harmful substances, small dimensions and weight. The luminous flux is characterized by uniformity and uniformity of luminescence. This type of illuminator has no pulsation or flicker. The devices are resistant to vibrations and can operate at temperatures ranging from minus 70 to plus 45 degrees.

It doesn't matter if you buy a spotlight in a store or build it yourself, its main characteristics include:

1. Luminous flux power. This parameter defines the maximum light that the device can give.
2. Focusing the glow. Indicates the angle of diffusion of light. If the angle of divergence of the light is large, then more area is illuminated, but the amount of light will be less.
3. Security. Since the device is operated outdoors, it is constantly exposed to the environment. Therefore, it is very important to protect the floodlight from dust, moisture or other substances and objects getting inside it.
4. Color rendering. This parameter depends on the type of emitters used. Describes how natural objects look under the light of the device.
5. Colour temperature. Depends on the type of LEDs used. It is believed that the color most comfortable for the human eye lies in the range of 2200-3000 K.
6. Nutrition. The illuminator requires electrical energy to operate. Therefore, the most common are devices that operate on a 220 volt alternating voltage network. But recently, devices that use the energy accumulated by solar panels for their work have become popular.
7. Additional functions. Manufacturers often equip their floodlights with different sensors that react to different changes. For example, it can be light or motion sensors.

Self-production

It is not a problem to buy an LED spotlight in a store, but it will be much cheaper and more pleasant to assemble it with your own hands. In fact, with the right approach, making this type of illuminator yourself is not particularly difficult, given that you can buy everything you need for this in stores. Here is a list of what you need to build a spotlight:

• reflector;
• body and elements for its connection;
• light emission matrix;
• driver;
• wires;
• sealant or glue.

Some materials will need to be bought, while others can be made from improvised means or even removed from old unnecessary devices.

Emitter array and driver

There are three types of LEDs. Super-bright white LEDs on a metal substrate or LED are used for the floodlight. Emitters made in plastic cylindrical cases with pin types are unsuitable for the manufacture of powerful floodlights.

As soon as the required number of LEDs or diode assemblies to obtain the required power is purchased, their installation on the substrate begins. Since the emitters get very hot during operation, you will need to mount them on the radiator. You can take any aluminum or copper plate as it. and cut out the required size from it, or you can use a ready-made radiator from a computer or other equipment.

For SMD LEDs, mounting holes are usually not provided, so they are glued to the radiator using heat-conducting glue. Once all the elements are glued, electrical contact will need to be made between them. To do this, using pieces of wire, all emitters are connected in parallel or in series to each other by soldering.

If a large number of LEDs are used, then it makes sense to use series-parallel connection. For this, branches are created, consisting of an equal number of LEDs with a series-installed limiting resistor. Its calculation is simple: the LED voltage is subtracted from the supply voltage and divided by the maximum permissible current.

The last value is defined as the sum of the currents of each element in the branch. As soon as the connection of the radio elements is made, a hole is drilled in a convenient place on the radiator through which a pair of wires is passed. One wire is soldered to the common plus of the LEDs and the other to the minus. On the back side, a margin of about four centimeters is made, which makes it possible to freely solder the driver.

Depending on the number of LEDs, you will need to make or purchase a power supply unit with the required voltage to ignite them. To do this, you need to know the characteristics of the LEDs used.

For a medium power floodlight, you can use general purpose power supplies with an output ripple current of up to two amperes and a voltage 3-5 volts higher than the forward voltage of the diodes. To avoid voltage surges that can lead to LED burnout, the driver must be stabilized. It can be done using integrated circuits: LM317, LM350 and LM338.

Assembling the elements together

As soon as the driver with the matrix is ​​ready, you need to decide on a case in which all the elements can freely fit. As it, you can use any unnecessary device suitable in size. For example, a computer power supply, an old spotlight with a light bulb. And you can do it yourself, but this will require locksmith skills.

In this case, you should immediately provide for the possibility of attaching the case to the walls or ceiling. Ordinary food foil is suitable as a reflector, and instead of protective glass, you can use transparent plastic, for example, from a CD box.

All elements are neatly placed in the middle. To secure them, it is easiest to use not threaded fasteners, but, for example, screeds or glue. But in the case of repairs, when the elements are glued to the body, the disassembly of the device will be significantly complicated. The plus from the LEDs is soldered to the plus of the driver, and the minus to the common wire. A connector for connecting to a 220 volt network or just a pair of wires is displayed on the case.

A test switch is made. If the searchlight has worked for about an hour, and its heating temperature has not exceeded 50-60 degrees, then you can confidently seal the case and start rejoicing at what you have done yourself device.