Charging LED. LED table lamp and its hidden capabilities. Selecting and connecting LEDs for illumination, night light

Regular readers are often interested in how to properly power LEDs to maximize their service life. This is especially true for LEDs of unknown production with bad technical characteristics or overpriced.

By appearance and parameters cannot determine quality. We often have to tell you how to calculate a power supply for LEDs, which one is better to buy or make yourself. Basically, I recommend buying a ready-made one; any circuit after assembly requires testing and adjustment.

1. Basic types
2. How to make the calculation
3. Calculator for calculation
4. Connection in the car
5. LED supply voltage
6. Connection from 12V
7. Connection from 1.5V
8. How to calculate the driver
9. Low voltage from 9V to 50V
10. Built-in driver, hit 2016
11. Characteristics

Main types

A LED is a semiconductor electronic element with low internal resistance. If you apply a stabilized voltage to it, for example 3V, a large current will flow through it, for example 4 Amperes, instead of the required 1A. The power on it will be 12W, and the thin conductors that connect the crystal will burn out. Conductors are clearly visible on color and RGB diodes, because they do not have a yellow phosphor.

If the power supply for LEDs is 12V with a stabilized voltage, then a resistor is installed in series to limit the current. The disadvantage of this connection will be higher energy consumption; the resistor also consumes some energy. For 1.5V LED rechargeable flashlights, it is irrational to use such a circuit. The number of volts on the battery decreases quickly, and the brightness will decrease accordingly. And without increasing it to at least 3V, the diode will not work.

Specialized LED drivers based on PWM controllers do not have these disadvantages. When the voltage changes, the current remains constant.

How to make a calculation

rated power consumption or desired;
drop voltage.

The total energy consumption of the connected electrical circuit should not exceed the power of the unit.

The voltage drop depends on how much light the ice chip emits. I recommend buying branded LEDs, such as Bridgelux, their variation in parameters is minimal. They are guaranteed to keep the declared characteristics and have a reserve for them. If you buy at a Chinese market, such as Aliexpress, then don’t expect a miracle, 90% of the time they will deceive you and send you junk with parameters 2-5 times worse. This was checked many times by my colleagues, who ordered inexpensive LED 5730 sometimes 10 times. They received SMD5730 at 0.1W, instead of 0.5W. This was determined by the current-voltage characteristic.

In addition, the cheap ones have a very wide range of parameters. To determine this at home with your own hands, connect 5-10 of them in series. I adjust the number of volts until they glow slightly. You will see that some shine brighter, others are barely noticeable. Therefore, some will heat up more in the nominal operating mode, others less. The power on them will be different, so the most loaded ones will fail before the rest.

Calculator for calculation

The calculator takes into account 4 parameters:

number of volts at the output;
voltage reduction on one LED;
rated operating current;
number of LEDs in the circuit.

Connection in the car

When the engine is running, there is an average of 13.5V - 14.5V, and when the engine is off, 12V - 12.5V. Special requirements when plugged into a car cigarette lighter or on-board network. Short-term surges can be up to 30V. If you use a current-limiting resistor, then the current increases in direct proportion to the increase in the LED supply voltage. For this reason, it is better to install a stabilizer on the microcircuit.

The disadvantage of using it in a car may be the appearance of interference on the radio in the VHF range. The PWM controller operates at high frequencies and will interfere with your radio. You can try replacing it with another one or linear type. Sometimes shielding with metal and placing it away from the car's head unit helps.

LED supply voltage

From the tables it can be seen that for low-power ones at 1W, 3W this figure is 2V for red, yellow color, orange. For white, blue, green it is from 3.2V to 3.4V. For powerful ones from 7V to 34V. These numbers will have to be used for calculations.

Table for LED at 1W, 3W, 5W

Table for high-power LEDs 10W, 20W, 30W, 50W, 100W

Connection from 12V

One of the most common voltages is 12 Volts, they are present in household appliances, in automobile and automotive electronics. Using 12V you can fully connect 3 LED diodes. An example is a 12V LED strip, in which 3 pieces and a resistor are connected in series.

Example on diode 1W, its rated current is 300mA.

If one LED drops 3.2V, then for 3 pieces it will be 9.6V;
the resistor will have 12V – 9.6V = 2.4V;
2.4 / 0.3 = 8 Ohms nominal required resistance;
2.4 * 0.3 = 0.72W will be dissipated by the resistor;
1W + 1W + 1W + 0.72 = 3.72W total power consumption of the entire circuit.

Similarly, you can calculate for another number of elements in the circuit.

Connection from 1.5V

The power source for the LEDs can be a simple 1.5V AA battery. An LED diode usually requires a minimum of 3V; there is no way to do this without a stabilizer. These specialized LED drivers are used in hand-held flashlights on the Cree Q5 and Cree XML T6. A miniature microcircuit increases the number of volts to 3V and stabilizes 700mA. Switching on from 1.5 volts using a current-limiting resistor is impossible. If we use two 1.5 volt batteries, connecting them in series, we get 3V. But the batteries run out quite quickly, and the brightness will drop even faster. At 2.5V there will still be a lot of capacity left in the batteries, but the diode will almost go out. And the LED driver will maintain the nominal brightness even at 1V.

I usually order such modules on Aliexpress, the Chinese cost 50-100 rubles, in Russia they are a bit expensive.

How to calculate the driver

draw up a connection diagram on paper;
if the driver is Chinese, then it is advisable to check whether it can withstand the declared power or not;
keep in mind that different colors (blue, red, green) have different volt drops;
the total power should not be higher than that of the current source.

Draw a connection diagram on which you will distribute the elements if they are connected not just in series, but in combination with parallel connection.

On a Chinese power supply from an unknown manufacturer, the power may be significantly lower. They easily indicate the maximum peak power, and not the rated long-term power. It is more difficult to check; you need to load the power supply to the maximum and measure the parameters.

For the third point, use the example tables for 1W,3W, 5W, 10W, 20W, 30W, 50W, 100W, which are given above. But trust more in the characteristics that the seller gave you. For single-chip ones there are 3V, 6V, 12V.

If the total power consumption of the circuit exceeds the rated power of the power source, the current will drop and heating will increase. He will recover before normal level, if you reduce the load.

For LED strips The calculation is very simple. Measure the number of watts per meter and multiply by the number of meters. Just measure, in most cases the power is overestimated and instead of 14.4 W/m you will get 7 W/m. All too often disappointed customers come to me with this problem.

Low voltage from 9V to 50V

I’ll briefly tell you what I use to switch on 12V, 19V, 24V units and to connect to 12V automobiles.

Most often I buy ready-made modules on PWM chips:

there are boosters, for example, 12V at the input, 22V at the output;
step-down, for example from 24V to 17V.

Not everyone wants to spend a lot of money on buying a ready-made spotlight for a car, an LED lamp, or order a ready-made driver. Therefore, they turn to me to assemble something decent from available components. The price of such modules starts from 50 rubles to 300 rubles for a 5A model with a radiator. I buy several pieces in advance, they sell out quickly.

The most popular option is the linear IC, a simple, reliable, outdated one.

Models based on LM2596 are very popular, but it is already outdated and I advise you to pay attention to a more modern one good efficiency. Such blocks have from 1 to 3 tuning resistances, which can be used to adjust any parameters up to 30V and up to 5A.

Built-in driver, hit 2016

At the beginning of 2016, LED modules and COB diodes with an integrated driver began to gain popularity. They are connected directly to a 220V network, ideal for assembling lighting equipment with your own hands. All elements are located on one heat-conducting plate. PWM controllers are miniature, thanks to good contact with the cooling system. We have not yet tested the reliability and stability; the first reviews will appear after at least six months of use. I have already ordered the cheapest and most affordable COB model at 50W. To find these on the Aliexpress Chinese bazaar, enter “integrated led driver” in the search.

Characteristics

Global problem, this is a counterfeit of Cree and Philips LEDs industrial scale. The Chinese have entire enterprises for this; they copy 95-99% of them externally; it is impossible for an ordinary buyer to tell the difference. The worst thing is when such a fake is sold to you under the guise of the original Cree T6. You will connect the fake one according to the technical specifications of the original one. A fake has characteristics that are on average 30% worse. Less luminous flux, lower maximum operating temperature, lower power consumption. You will not find out about the deception very soon; it will work about 5-10 times less than the real one, especially at double current.

Recently I measured the luminous flux of my flashlights on the left Cree made by LatticeBright. I took out the entire board with the driver and placed it in a photometric ball. The result was 180-200 lumens, the original had 280-300 lumens. Without serious equipment, which is mainly found in laboratories, you will not be able to measure and therefore find out the truth.

Sometimes you come across overclocked diodes, the current on which is 30%-60% higher than the rated one, and accordingly the power. An unscrupulous manufacturer, especially a basement Chinese one, takes advantage of the fact that service life is difficult to measure in hours. After all, no one records the time worked, and when a lamp or LED spotlight fails, the seller can no longer be found. And there is no point in searching, the warranty period for such products is always shorter than the service life.

Almost everyone has an unnecessary charger from an old phone lying around. This is a great thing to use in a few steps to make yourself LED backlight in the hallway, on the staircase and porch, in the closet, or whatever night light, or wherever your imagination allows.

Backlight, night light from charger

So, we take a charger, its output voltage is about 5 volts, and we buy two or more LEDs in a radio goods store (and sometimes electrical goods stores). The number and type of LEDs will largely depend on what we want to achieve and what our purposes or objects of illumination are. When buying LEDs, you need to remember to buy PVC tape here - www.avalon-pack.ru/izolenta.html, for example, and mounting connectors for connecting if you don’t have a soldering iron or don’t want to do soldering, and one or two resistors. The photo gives an idea of the device. It remains to find out about the important details.

Selecting and connecting LEDs for illumination, night light

The first thing you need to know is that LEDs need a voltage of 3.0 volts. But they also work at lower voltages. LEDs come in white, yellow, red, blue and green. Typically, the operating current is two times higher than that of white and yellow LEDs. LEDs only work with the correct polarity. For LEDs with flexible leads, a longer contact is a “plus”. Accordingly, a shorter output is a “minus”.

Since the power supply voltage is about 5 V (idle), we will connect two LEDs in series, which will provide power to each LED with a voltage of approximately 2.5 V. We will set the operating current with a resistor that is connected in series in the circuit, as indicated in the photo. If LEDs are used white, then the nominal value of the resistor needs to be about 300-400 Ohms (standard value is 360 Ohms). If the LED is red or green, the resistance should be taken at a nominal value of 2 times less. And if bright LEDs are used (in the second figure above), then they operate with significant currents; the resistor value, depending on the desired brightness, can be within tens of ohms.

With very low resistance, bright LEDs will get very hot and need to be attached to a metal radiator with an area of 12-20 cm square. You can connect two LEDs without a resistor. But then they will not work in the nominal mode and will fail faster. Large resistance values will reduce the brightness of the LEDs.

For illumination, it is better to use high-brightness LEDs; they have a low price, equivalent to $0.15-0.3 (such an LED is in the first photo, and bright ones with a radiator are in the second photo above, but they are much more expensive). The current consumption of LEDs of the first type is only 10-20 mA, which will allow you to use the backlight around the clock or during the entire dark period of the day, providing very, very low power consumption. These LEDs emit a directional beam of light with different specified angles of luminous flux, which the store should tell you about. They also sell optical lenses that form the luminous flux at the angle specified by the lens you purchased (30 or 60 degrees).

You can use such lighting from a combination of red, blue, green LEDs for the hallway, in the bathroom, on the porch of a private house, and you never know where else.

How to connect large quantity LEDs? Possible, if power (current) allows charger or power supply. To do this, connect several such chains as in the photo (but always with resistors) in parallel. At the very least, you can try to turn on 4-5 pairs of such LEDs, although you can experiment with a larger number of them.

Connecting LEDs without a charger

Is it possible to do without a power supply, for which there may not be a necessary socket, or it will worsen the design? You can, and there are at least two options here. The first is to connect the diodes directly to a 220 V power supply. However, this work is best done by a person who has solid skills and knowledge in electricity, since carelessness when connecting can lead to tragedy. If you are confident in your skills, then use one LED without a power supply, but include two resistors, one to the long flexible lead and the second to the short lead of the LED, each rated at approximately 22,000 ohms (22 kohms). The diode leads must be tightly insulated with electrical tape to prevent contact with them. Connect only to the mains in a de-energized state, unless you connect the LEDs using a plug to an electrical outlet. Such LEDs can only be hung high in a place inaccessible to others. Such a backlight will shine with much less brightness, since resistor values have been chosen to prevent breakdown of the device by reverse voltage. The reduced brightness is also due to the LED being powered by only one half-wave of alternating voltage. You can improve the brightness by turning on two LEDs in parallel, but the terminals must be connected oppositely - on each side, connect the long one to the short one (and a resistor to each combined terminal). As a result, power will be provided at the moment to one of the LEDs with a positive half-wave, and the second with a negative half-wave. Practice, however, shows that with such a connection, LEDs quickly fail.

The second method of discarding the power supply is to use a galvanic battery (battery) or a battery from a phone. A 1:1 scheme is used, as in the photo, but instead of a power supply, a battery is taken. A 3R12 flat battery with 4.5 V flexible leads, or AA batteries in special containers that are sold in radio stores, are well suited for this. You can connect one LED to a container with two AA batteries, and two LEDs in series to four elements, as in the photo. Experience has shown that LEDs powered by a 3R12 element emit light for many months without significant discharge. In the same way, batteries from radiotelephones (which need to be charged) can be used for these purposes, but the power supply is 3.6 V, when you can connect one LED or several of them in parallel.

How to determine voltage polarity in power supplies

Yes, power supply from mobile phone has inappropriate connectors for connecting power to other consumers, what should I do? In the Nokia charger, the cylindrical connector has a “plus” in the center and a minus on the outside. In others, simply cut the wire. One wire will be “plus”, one will be “minus”. ( Read the next page, numbered below)

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Review of a 2 in 1 LED table lamp, the lamp performs its function of illuminating the table but can also charge a smartphone, the stand contains a wireless charger and if your smartphone has such a function, you can put it on the stand and the smartphone will be charged with a small current, but more on that below.

The package is large but very light, the box has a nylon rope, very convenient to carry the lamp. I didn’t throw away the box, but it came in handy later.

The manufacturer Baseus produces mainly components for smartphones and has recently expanded its product line with LED lamps.

Specifications

LED life: 50000hrs
Wireless transmission distance: Less than and equal to 8mm
Charging efficiency: More than and equal to 75 percent
Input: 5V/2.5A
Output: 5W Dimension and Weight
Product weight: 0.465 kg
Package weight: 0.770 kg
Product Size(L x W x H): 40.00 x 20.00 x 11.00 cm / 15.75 x 7.87 x 4.33 inches
Package size (L x W x H): 46.00 x 15.50 x 5.00 cm / 18.11 x 6.10 x 1.97 inches

The power supply has a Chinese plug and has a built-in cable with a microUSB output; there was no adapter for a European plug.

The lamp itself looks good, the white plastic is glossy and was protected by a layer of polyethylene, the gray stand is made of aluminum.

The LEDs are hidden under a diffusion film.

The control panel is touch-sensitive, the buttons are highlighted only when active. The red LED in the center is lit - this is the wireless charging center.

The LED lamp has only one microUSB input; the lamp has a soft base.

First, measurements with a tape measure.

Group photo with the previously most popular table lamps.

The lamp is controlled using a touch panel; there are four color temperature modes from warm to cold glow: 2800 - 3400 - 4500 - 5600.

There is a timer for 1 hour and two hours (1h - 2h), can be used as a night light.

Perhaps the downside to using a lamp is that it bends in only two places and it won’t be possible to place it so that it only illuminates the keyboard.

At minimum lighting, the current consumption is 0.2A.

At maximum illumination, the current consumption is 0.8 A.

I showed how the lamp works, now I’ll move on to the wireless charger. I have one device that has wireless charging function: Samsung S6.

As experiments have shown, the charger works the same with and without a case, that is, the charging current is on average 0.4A, of course LED lamp it does not shine.

With the LEDs turned on to maximum, the current consumption increases to 1.3A, the wireless charger still remains within 0.4A.

Now I'll move on to opening the lamp. I’ll say right away that what I saw surprised me a little, but then I thought it was the Chinese, but the Chinese manufacturer Xiaomi would not allow this.

Under the plastic touch panel there is a control board. In the center is a wireless charger, what immediately caught my eye is that this very device has a microUSB port and I would say that there would be enough space for charging with three windings.

But it gets more interesting. You can’t understand the logic of the Chinese, they live in a different world, what I mean is that on the back panel there is not one microUSB port, but also another USB output port. If it had not been soldered, I would have understood it, it is not allowed in this revision, but it is there, but there is no hole for it. I looked at a review of this lamp on the store’s website and there is also no USB output.

I checked the USB is working and the output output is no more than 1A, so I cut a hole for the USB output.

I almost forgot, the LEDs are covered with aluminum foil, this is done so that the top white plastic cover does not glow.

The LEDs are 48x4014, and judging by the design, you can install a second panel with LEDs on the back side. The diffuser is very simple - an acrylic strip, onto which several strips of matte tape are glued in several layers. This is the simplest solution, but it gets the job done.

The lamp is located behind the monitor and when necessary I turn on the table lamp, it shines, it shines behind the monitor, it turns out to be a good night light. The smartphone often lies on recharge, now I don’t worry about connecting the charging cable, which is not bad, well, that’s what the lamp was purchased for.

The lamp left an ambiguous feeling, everything seemed to work and suit me, but on the other hand, the Chinese left room for a more powerful wireless device, that is, they saved money and installed a cheap one. If you remove the weighting material and put in a flat li-ion battery and install a charge controller, you will get a self-contained table lamp. These are the hidden possibilities that I will deal with in the near future.

I have a charge controller, now I need to find a suitable flat battery and if anyone can tell me where to buy good batteries from me +.

The lamp was bought with my own money.

I'm planning to buy +11 Add to favorites I liked the review +55 +74