USB backlight for keyboard. Homemade keyboard backlight

Probably everyone is familiar with the situation when you have to work at a laptop (typing text, or processing other information) in the dark, but for one reason or another you cannot turn on the light.

Something made by yourself will help you cope with this problem. laptop keyboard backlight. Without exaggeration, anyone who is at least a little familiar with electronics and can hold a soldering iron can make it. So, fewer words, it's time to get down to business.

To work, we will need: soldering accessories, a resistor with a resistance of 820 ohms, a ferrite ring (can be taken from any motherboard, or computer unit power supply), a little cross cutting, heat shrink tube, thick wire, any npn transistor, in my case KT3102, bright white LEDs, you can use standard round ones. Or maybe not just LEDs, as in my case. I had a broken matrix from a laptop, and I used part of the backlight strip from it.

Let's start manufacturing by winding the transformer (if you can call it that) on a ferrite ring. To do this, you need to evenly lay 18–22 turns of wire around the entire perimeter of the ring. You need to wind with two wires at the same time; for convenience, it is better to take wires with insulation of different colors. The end result will be something similar to this:


Next, connect the end of the white wire to the beginning of the blue one. The plus of the USB connector will be connected to this solder. We connect the beginning of the white wire through a resistor (it is necessary to install it, otherwise the transistor will heat up, and the transformer will whistle and nothing will work) to the base of the transistor. By the way, the pinout of the transistor, if you look at it not from the cut side, is emitter base collector. We connect the collector to the end of the blue wire. Later, the minus from the USB connector will be connected to the emitter. The LED strip is connected with a plus to the collector and a minus to the emitter. The design of this homemade lighting device is simple and clear, so I am not attaching a diagram.



All the nuances are visible and understandable from the photo. Other rants about the design of this homemade product - laptop keyboard backlight inappropriate. Everyone will work out the design and construction for themselves. Based on available materials. Don't limit your imagination.

Nowadays housewarming is not celebrated. The tradition is lost. And before they invited guests. Guests came with gifts, including a chandelier. It was difficult to buy a chandelier; there were too few of them produced. Nowadays it’s difficult to buy any lighting device; they produce too many of them - your eyes run wild from the assortment. And so, when all the design projects were implemented, and there were no free sockets left in citizens’ homes, there was one of the advanced ones who pointed his finger at computer sockets. This is how a new product niche emerged. LED niche.

I bought this as a future souvenir for someone who likes to communicate with a netbook. Its full name is “FLARX USB LED lamp”. There is not a lot of information on the packaging, but it is quite enough to make a choice. Composition: polystyrene, steel. LED lifespan: 10,000 hours (which is impressive).

The openwork reflector in the shape of flower petals immediately makes an impression; its diameter is 85 mm, the total length of the lamp is 350 mm, the thickness of the flexible element is 5 mm, the USB plug is standard. It looks beautiful. However, it immediately becomes clear that the thin plexiglass petals will not last long.

In terms of overall dimensions, the lamp fits in with the overall appearance of a netbook, but in terms of design, it’s not very good, but functionally it’s definitely not. The LED glow is so weak that with additional lighting it cannot be seen at all. The verdict is simple - something needs to be done.

It was not possible to remove the reflector using the force of the fingers; a hacksaw blade was called in to help, which made a circular cut in the holder. After which it was safely disconnected from the flexible element. The LED itself and its resistor - the current limiter - appeared. The measurement established the resistance of the resistor - 58 Ohms. The solution is simple - you need to reduce it. The reflector petals were not glued and were removed from its lens freely. The diameter of the spherical light-scattering lens, also made of organic glass, is 24 mm.

New electrical circuit of the lamp

A certain suitable plastic part was put on the now free end of the flexible element, which was intended to subsequently act as a base for attaching a variable resistor. The constant resistor, as a circuit element, was left, but its value was reduced to 23 Ohms. A hole with a diameter of 2 mm was drilled in the side boss of the lens mount, through which connection wires with a variable resistor needed to regulate the strength of the light flux were passed.

With a total resistance of the limiting resistors of 493 Ohms (variable 470 Ohms and constant 23 Ohms), the current on the LED is 4.3 mA. We obtain the minimum possible luminous flux. With the variable resistor turned to “zero” and, accordingly, only the resistance of the constant resistor at 23 Ohms, the current on the LED is 47.3 mA. This is the maximum luminous flux. Well, the “truth” is that the best ratio of LED load and illumination will be somewhere in the middle.

The base for mounting the LED is hollow; drilling holes in it, passing wires through them, and then soldering it to a variable resistor was not particularly difficult, as was installing the resulting regulator in place. The internal cavity was filled with Titan glue. In conclusion, a kind of lampshade was made and installed; it has no reflective abilities, but it will save the eyes from unnecessary light.

The keyboard backlight is in action: in a room in daylight and in a dark room. It is turned on at maximum brightness, it is quite possible to turn it down to normal.

It is already clear that, if necessary, a netbook with such keyboard lighting can be fully operated in this way. The beauty of the product has undoubtedly diminished, but it has become functionally suitable for the intended work. In general, I was in a hurry to buy this particular model; now more suitable keyboard lighting functions have appeared on sale. Review made Babay iz Barnaula.

Discuss the article USB LIGHT FOR KEYBOARD BACKLIGHT

At the moment, the market offers many options for organizing lighting for the place at the computer or the work area near it. One of the most optimal ones are LED strips, powered by a USB connector. In this article we will look at which LED strips can be connected to USB port, connection diagrams, some nuances and features. We will also consider power supply technology LED strip directly from the computer's power supply.

Why connect an LED strip to a computer?

In areas where computer equipment is located, it is often necessary to install additional lighting. For example, not to use the main lighting of the room. It may interfere with other family members when using the computer at night. Or switch off to save money. The light from the monitor may not be enough. Also, the presence of backlighting eases the strain on your eyes when working on a PC.

USB backlight option for the system unit itself

Computer workstation illumination with LED strip

Powering the LED strip from a PC allows you to solve these problems. Installation of the tape is possible in any necessary place and to perform various functions:

  • monitor backlight;
  • keyboard backlight;
  • additional lighting of the work area.
  • decorative design of a table or room interior.

The tape can be powered via a USB output or directly from the computer's power supply. The use of such power sources eliminates the need for:

  • stretch additional wires, of which there are always plenty near the computer and often get tangled;
  • take up space in the outlet, which is also sometimes not enough, especially if you have additional office equipment.

Using a USB LED strip allows you to save power consumption, since the strip uses little - up to 5 W.

Which LED strips can be connected to a PC via USB

At the output of the computer's USB port, the voltage level is not high (up to 5 volts). There are basically two options for connection:

  1. Connecting a ready-made LED strip model with a built-in converter and USB plug. This factory-made tape implies an input voltage of 5 V; for operation you just need to connect it to a USB port.
  2. The second option is to assemble a circuit using a 12 V LED strip and a voltage level converter from 5 V to 12 V.

Also, LED strips connected to a USB port are divided by emitted color:

    • Monochrome – emits white constant light;
    • RGB or tri-color - emits three primary colors, red, green and blue.

Connection features

Connecting the LED strip via a USB port is carried out if it is impossible or unwilling to get inside the computer, as well as when using a laptop. When assembling the circuit, it is necessary to take into account that to power the tape, a voltage level of 12 V is required. To do this, you need to make or buy a ready-made voltage converter from 5 to 12 V in a radio parts store.

It is worth considering that the USB port produces no more than 500 mA. When introduced into the converter circuit, the current is reduced to 200 mA. Therefore, you should use an LED strip with the same or lower current parameters.

To assemble the converter, you can use a factory PWM controller, for example LM2577, this will reduce the number of parts of the converter. The following parts are also required according to the diagram: USB plug, connecting cord.

Converter circuit:

This circuit is considered universal and makes it possible to obtain the desired output voltage. Its parameters depend on resistors R1 and R2. The result is a pulse-width converter. The capacitance of the capacitors at the input and output of the power supply must be in the range indicated in the diagram. These capacitors are designed to smooth out DC voltage ripples.

The resistor and capacitor at pin 1 are the frequency-setting circuit. Their parameters must be strictly observed according to the scheme. The inductance of the coil between points 4 and 5 should be clearly 100 μH. The diode must meet special conditions. It must have high performance, and also a slight reduction in voltage at the junction. The ideal option is a high-frequency Schottky diode. The brand of diode is not very important, since this circuit has an insignificant level of voltage and current.

Next you need to connect the wires and the USB connector. To do this, it is convenient to use a detachable USB plug. It has 4 contacts. To connect, you only need two on the edges, which provide power. Their polarity can be determined with any voltage measuring device by connecting the plug to the socket.

The circuit is mounted on a printed circuit board made of foil fiberglass, and as a result the device has approximately this appearance:

Ready-made power converter for LED strip connected to a computer

If you have certain skills and knowledge, it is not difficult to assemble such a circuit. The most important thing is to strictly follow it and observe the location of the parts.

Connecting an LED strip from a PC power supply

The technology for connecting from a PC power supply is a little simpler than the previous method. With this connection, there is no need to break the warranty seal on the power supply and disassemble it. Almost every power supply is equipped with additional connectors. The wires can be like this:

Power supply connectors personal computer. In our case, we use option 1 or 2.

Connectors of types 1 and 2 are suitable for connecting the LED strip. The first one is used to connect a practically unused “flop” for floppy disks. Number 2 for connecting a hard drive and CD/DVD-ROM. Both jacks have 12 volt output and are available for use. To connect, you need black and yellow wires. Black is a minus.

The connection technique is extremely simple; the necessary wires are disconnected or simply bitten off from the selected connector and soldered to the LED strip, observing polarity. But in the future, nothing can be connected to this connector.

If you plan to use the connector or simply don’t want to break the circuit, you can buy an adapter and cut the wires on it.

Adapter for power supply, suitable for connecting LED strip. You only need to use two wires, the rest need to be insulated.

BP modern computers They are quite powerful and can be used to connect LED strips up to several meters long. Data on power and current are indicated on the power supply itself. In most cases, there is always a power reserve that can be used to connect an LED strip.

When calculating the length of the tape, the following table will help, since the tapes do not always contain information about the consumed load.

The table is very useful when calculating the length of the LED strip to be connected to the computer

Approximate calculation of the length of the tape. If the power supply has a current reserve of 4 or more amperes, then you can safely connect an SMD 3528 tape with a density of 120 diodes per meter, 4 meters long, or a 3-meter SMD 5050 with a density of 60 diodes.

The length and type of tape are calculated similarly when connected from a USB port.

Ready solutions

For those who do not want or are simply unfamiliar with the world of electronics, the modern market offers many ready-made options for LED strips connected to a USB port. They may differ in appearance, but in general they work on the same principle. Examples of ready-made solutions:

The first option is an RGB LED strip connected to the computer’s USB port

The second option is a one-color LED strip for connecting to a computer via a USB port

The first option is RGB tape with a connected RGB converter. The set includes a control panel that allows you to adjust the brightness of colors and their shades. The second option is a 30 cm long monochrome LED strip. Both options simply connect to a USB port and do not require additional devices.

An LED strip connected to a USB port is a good option for organizing lighting near a computer. Its use allows you to save on energy consumption; it does not take up much space, like a table lamp. The technology for connecting an LED strip to a computer is generally simple and does not require serious financial investments. In addition, there are many already assembled models that can simply be connected to a USB port.


In this material we present to your attention an overview of the most interesting idea for making a USB backlight for a laptop keyboard.

We will need:
- glue gun;
- soldering iron;
- USB plug;
- cap from a plastic bottle;
- tester;
- Light-emitting diode;
- 100 Ohm resistor.

First of all, we take a tester and determine which resistor is suitable for us to make the backlight.


Take a USB plug. The first and fourth pins of the plug are positive and negative. The second and third contacts are for data transfer. Let's start assembling.


Solder the resistor to the negative terminal. The polarity of the resistor does not matter in this case.




Let's move on to the LED. The positive side of the LED is called the anode, and the negative side is called the cathode. On new LEDs, the anode leg is longer than the cathode leg. If you are using an LED that has been previously used, then the polarity can be distinguished by the sawn-off skirt or bed of the crystal, which is located on the cathode.


Solder the negative of the LED to the resistor.




We solder the positive leg of the LED to the positive contact of the USB plug.




We insert the plug into the connector and check the assembly for functionality.


We put a mark on the plug, bend the resistor and LED into the desired position, fill the cap of a plastic bottle with hot glue and immerse the resistor with the LED light bulb and plug up to the mark.






The lighting itself is ready. If desired, you can paint it with spray paint.

After a store-bought USB keyboard backlight broke on the first day of use, I decided to make my own. For this you will need:
1) USB plug to type A socket
2) LED
3) Resistor
4) Telephone cable TRP
5) Soldering iron, solder, rosin
6) Scissors or knife
7) Pliers (pliers)

USB plug we need it in order to supply power from the USB output. There are several types of USB outputs, most computers use type A. The pinout of these outputs can be viewed or. I bought a USB plug in a store, so it looked like this:

You need to solder telephone wires to the white thing on the side that will be inside.
First, you need to cut off a piece of cable of the length you need, then cut it in half (two-core cable) and clean it of excess insulation. The edges of the resulting wires should be completely stripped of insulation by carefully cutting through the insulation to the wire around it and removing it. Then, one wire should be cut by 1-1.5 centimeters - a resistor will be soldered to it. We solder the stripped ends of the wires to the outer pins of the USB plug, these are the power outputs, the middle pins are connected to each other with a small lump of solder, these are the differential information outputs.
In order to solder, you need to preheat the soldering iron by turning it on, then (after 10-15 minutes) melt a little rosin, then solder, pick up a drop of solder on the soldering iron and apply it to the previously connected surfaces to be soldered.
It’s good to check with a multimeter in continuity mode whether you have shorted “extra” pins - only pins 2 and 3 should be closed. Using the links given above, you should also look at the polarity of the pins, and mark the wires at both ends so that it is clear to you where there will be a positive potential, where there will be a negative one.
Then we insert the white piece into the piece of hardware, plug it with a second piece of piece of hardware, and use pliers to crimp the place where the wires come out so that the USB plug cannot come loose.
Light-emitting diode I bought it at the store. I would choose a bright or ultra-bright LED with a luminous intensity of at least 5 candelas. The color is up to your taste, I chose blue. You should remember and note the parameters of the LEDs, such as their operating voltage and current. The LED should be connected taking into account the polarity - the cathode to the positive potential, the anode to the negative. You can see the polarity in this picture: As you can see, the shorter terminal is the cathode, the longer one is the anode. You can also look at the light to see how the glands in the LED stand, compare with the picture and find out the polarity.
Resistor selection. The resistor plays a very important role - it limits the current so that the LED does not burn out. The voltage at the USB output is standard and stabilized (does not depend on the current) - 5 volts, the current can vary from 0 to 500 milliamps. In theory, if the LED has an operating voltage of U, then we need the remaining voltage of 5-U to drop across the resistor, and the current is operating for the LED (we connect the LED in series to the USB output). Thus, to connect an LED with an operating voltage U<5В и током I<500мА нужен ограничивающий резистор номиналом (5-U)/I. For example, my LED consumes 3.5 V and 0.02 mA, which means I took a resistor of (5-3.5)/0.02 = 75 Ohm. However, there may not be such a specific resistor in the store - then you need to take the first resistor, which is close in nominal value to the calculated one, but larger, so that the LED current does not exceed the nominal one and the LED does not burn out. Of course, you should not take, for example, 100 Ohms instead of 75; it is desirable that the resistance deviation does not exceed 10% of the calculated value. And don’t take ceramic resistors instead of regular ones - they are very bulky.
If you have old resistors, you can measure their value using a multimeter, or try to determine the value by color markings using this table:
So, after soldering a resistor to the short end of the wire and soldering the LED (maintaining polarity), you can connect the USB backlight. If the LED starts to shine, then everything is fine, but if it does not light up, gets very hot and after a while a distinct burning smell appears, then you have reversed the polarity and the LED has burned out. If the LED does not light up and there is no burning smell, then most likely you have shorted the information pin with the power pin, or have not connected them to each other - you can open the plug and re-solder it.
The end result is this design:



The cost of this design was only 29 rubles, taking into account the costs of parts, not taking into account the costs of transporting parts and purchasing tools.
It shines well in the dark (7 candelas), does not dazzle the eyes, but the letters on the keyboard are visible.

Tags: electronics, amateur

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