As indicated by plus and minus on the board. Plus and minus for the LED. Determine the polarity of the LED. Determination of polarity by alternative methods

This integral element of almost all electric / circuits is available in several modifications. The need to determine the polarity of a capacitor refers to electrolytic capacitors, which, due to their design features, are something in between a semiconductor and a passive circuit element. Let's see how this can be done.

Methods for determining the polarity of a capacitor

By marking

Most domestic electrolyte capacitors, as well as a number of states of the former socialist camp, have only a positive conclusion. Accordingly, the second is a minus. But the symbolism can be different. It depends on the country of manufacture and the year of manufacture of the radio part. The latter is explained by the fact that over time they change regulations, new standards come into force.

Capacitor plus sign examples

• The "+" symbol is on the body near one of the legs. In some episodes, it passes through its center. This applies to capacitors of a cylindrical shape (barrel) with a plastic "bottom". For example, K50-16.
• For capacitors such as IT, polarity is sometimes not indicated. But you can determine it visually if you look at the shape of the part. The “+” terminal is located on the side with a larger diameter (plus in the figure above).

• If the capacitor (the so-called coaxial design) is intended to be mounted by connecting the case to the “chassis” of the device (which is a minus of any circuit), then the central contact is a plus, without any doubt.

Minus sign

This applies to imported capacitors. Near the “-” leg, on the body, there is a kind of barcode, which is a discontinuous strip or a vertical row of dashes. Alternatively, a long strip along the centerline of the cylinder, one end of which indicates a minus. It stands out against the general background with its shade.

Geometry

If a capacitor has one leg longer than the other, then this is a plus. Basically, imported products are also marked in this way.

With a multimeter

This method of determining the polarity of a capacitor is practiced if its marking is difficult to read or completely erased. For verification, you need to assemble a circuit. You will either need a multimeter with an internal resistance of about 100 kΩ (mode - measurement I \u003d, limit - microamperes)

or dc supply + millivoltmeter + load

What to do

• Discharge the capacitor completely. To do this, it is enough to short-circuit its legs (with a screwdriver sting, tweezers).
• Connect capacitor to open circuit.
• After the end of the charging process, fix the current value (it will gradually decrease).
• Discharge.
• Re-include in the diagram.
• Read the instrument readings.

If the positive probe of the multimeter was connected to the "+" of the capacitor, then the difference in readings should be negligible. If the polarity is reversed (plus or minus), then the difference in the measurement results will be significant.

Recommendation. It is advisable to determine the polarity by the device in any case. This will make it possible to simultaneously diagnose the part. If the electrolyte, which has a large denomination, is charged relatively quickly from a 9 ± 3 V source, then this is evidence that it has dried out. That is, it has lost some of its capacity. It is better not to put it in the circuit, since its work may be incorrect, and you will have to deal with additional settings.

One of the important steps in assembling a computer involves connecting the wires to the motherboard. Considering that there are enough different compounds there, some points should be clarified. And although power supplies try to make all connectors intuitive for the user, sometimes problems arise.

Motherboard wiring instructions (MSI, ASUS, ASRock, etc.)

Note right away that the example below is not true for all models and types of boards. It describes the general picture of connecting wires to the motherboard, but all sorts of small differences can always be present. We'll start by connecting the connectors. It is assumed that the motherboard is already screwed onto the case and ready to plug in. Also, the power supply is already installed and screwed on.

Connecting connectors

The very first stage is connecting the Power, Reset buttons on the case panel. We will also connect the power supply for the LEDs, which perform the function of indicating the operation of the computer. These wires are directed away from the front of the case and are in different colors (yellow, red, etc.). There are connectors at their end. Each of them has a special abbreviated marking. They need to be connected to the motherboard in the slots designated specifically for them.

It is worth noting that all connectors are protected against incorrect connection, so you are unlikely to be able to insert a connector into an unsuitable connector. It is important that the connection is smooth, effortless.

The connector that comes from the power button on the case is labeled M / B SW. Open the instructions specifically for your motherboard and see where you need to insert it. It has no plus or minus, so it can be inserted either side.

The second connector is responsible for the reset button, it is marked RESET SW.

There are also two small single connectors with plus and minus indication and POWER LED + and "-" markings. They are responsible for indicating the operation of the computer. It is important not to confuse "plus" and "minus" in places, so be sure to check the instructions.

Light-emitting diode hard disk without plus and minus indication is marked as H.D.D LED. However, it must be installed with a white wire to minus.

To be able to connect headphones to the case, and not to the motherboard, you need to connect the AUDIO connectors. The sockets on the motherboard are also labeled AUDIO, but check the instructions before connecting.

The same is with the connectors for connecting USB interfaces. They need to be inserted into the slots on the board marked USB. Recall that if the connection of wires to the motherboard of Asus (or other manufacturers) is carried out with great effort, then there is a possibility that you have made a mistake with the socket or connector. The latter are protected against incorrect connection, and you simply cannot physically insert them into unsuitable slots.

Most often, the jacks for connectors are in the lower right corner - look for them there.

cpu power

Now it's about connecting the wires to the motherboard that come out of the power supply. First of all, we connect the processor. The socket for its power supply is always located next to the processor itself, but we will not indicate the exact location, since it is individual for different models.

So, a 4-wire wire comes out of the power supply and connects to the processor socket. Most likely, it will be the only one on the motherboard, so you are unlikely to be able to insert the connector into any other slot. And yes, it also has a special key to prevent the wrong inclusion.

Main cable connection

The main power cable for the motherboard is the largest. In addition to this, there is a separate 4-wire connector. Take them together and plug them into the motherboard in one single existing connector. The connectors have special latches. Therefore, when connecting, make sure that this entire massive structure snaps into a special protrusion in the connector itself.

RAM

Planks random access memory are connected without wires. The contact method is used here. For RAM there are special slots with latches. They need to be pushed aside and slots (or a slot, if there is only one) inserted in the only correct way due to the cut in the slot and on the bar itself. You need to insert the bar carefully, pressing slightly from above. The clamps should gradually converge and click into place as a result.

Be careful not to press hard or the motherboard will bend. Thus, it is necessary to insert all the strips.

Connecting SATA and IDE devices

The hard drive is connected to the motherboard using a special SATA cable. It is usually red in color. The SATA cable has the same connectors on both ends. Connect one to the hard drive (there is also a key to prevent the wrong connection), and the second to the connector on the motherboard marked SATA 1. Usually, motherboards have 2-4 such connectors. You can choose any. After connecting the SATA cable, connect the power. In the rightmost hole (usually the rightmost one), plug in the connector to which 4 veins from the power supply are connected.

An optical drive is connected via an IDE cable. But today, modern computers are not equipped with disk drives due to their uselessness.

Connecting a video card

The final stage of connecting wires to the motherboard is installing a video card. It fits into a PCI-E slot, which is labeled accordingly. In fact, you will not be able to insert a graphics chip into any other slot. Depending on the model of the motherboard, the video card is fixed or not fixed with a special clip, but it is always attached to the case with a screw.

Powerful video cards need additional power from the unit. If there is a power connector at the very end of the video card, be sure to use it. After connecting, we have no free wires from the power supply. However, they may remain in the event that you do not have an optical drive installed. At this point, the instructions for connecting the motherboard wires can be considered complete.

Close the case cover and turn on the computer. Everything should work. But even if, when connecting wires to (or another brand), you forgot to supply power to any component, then there is nothing wrong with that. The computer just won't start, but it won't hurt anything.

Any DIY and electronics lover uses diodes as indicators, or as lighting effects and lighting. In order for the LED device to glow, you need to connect it correctly. You already know what the diode is conducting. Therefore, before soldering, you need to determine where the anode and cathode are at the LED.

You can find two LED symbols on the circuit diagram.

The triangular half of the designation is the anode, and the vertical line is the cathode. The two arrows indicate that the diode is emitting light. So, the diagram indicates the anode and cathode of the diode, how to find it on a real element?

5mm diode pinout

To connect the diodes as in the diagram, you need to decide where the plus and minus of the LED are. To begin with, consider the example of common low-power 5 mm diodes.

The figure above shows: A - anode, K - cathode and schematic designation.

Pay attention to the flask. Two parts are visible in it - this is a small metal anode, and a wide part similar to a bowl is a cathode. The plus is connected to the anode, and the minus to the cathode.

If you are using new LED elements, it is even easier for you to pinout them. The length of the legs will help determine the polarity of the LED. Manufacturers make a short and long leg. Plus is always longer than minus!

If you are not soldering a new diode, then the plus and minus is the same length. In this case, a tester or a simple multimeter will help determine the plus and minus.

How to determine the anode and cathode of diodes 1W or more

In 5mm floodlights, samples are used less and less, they were replaced by powerful elements with a capacity of 1 watt or SMD. To understand where the plus and minus are on a powerful LED, you need to carefully look at the element from all sides.

The most common models in such a case have a power of 0.5 watts. In the figure, the polarity mark is circled in red. In this case, the plus sign marks the anode of the 1W LED.

How do I know the polarity of SMD?

SMD is actively used practically in any technique:

• Light bulbs;
• lED strips;
• flashlights;
• indication of something.

You won't be able to see their insides, so you need to either use instruments for testing, or rely on the LED case.

For example, the SMD 5050 case has a corner mark in the form of a cut. All leads located on the side of the label are cathodes. There are three crystals in its body, it is necessary to achieve high brightness of the glow.

A similar designation for SMD 3528 also indicates the cathode, take a look at this photo of the LED strip.

The marking of the SMD 5630 pins is similar - the cut indicates the cathode. It can also be recognized by the fact that the heat sink on the bottom of the case is displaced towards the anode.

How to determine a plus on a small SMD?

In some cases (SMD 1206), you can find another way to indicate the polarity of LEDs: using a triangle, U-shaped or T-shaped pictogram on the surface of the diode.

The protrusion or side to which the triangle points is the direction of current flow, and the terminal located there is the cathode.

Determine the polarity with a multimeter

When replacing diodes with new ones, you can determine the plus and minus power of your device on the board.

LEDs in spotlights and lamps are usually soldered on an aluminum plate, on top of which a dielectric and conductive tracks are applied. On top, it usually has a white coating, it often contains information about the characteristics of the power supply, sometimes the pinout.

But how to find out the polarity of the LED in a light bulb or matrix if there is no information on the board?

For example, on this board, the poles of each of the LEDs are indicated and their name is 5630.

To check for serviceability and determine the plus and minus of the LED, we will use a multimeter. We connect the black probe to negative, com or a socket with a ground sign. The designation may differ depending on the multimeter model.

Next, select the Ohmmeter mode or the diode test mode. Then we connect alternately the multimeter probes to the diode terminals, first in one order, and then vice versa. When at least some values \u200b\u200bappear on the screen, or the diode lights up, then the polarity is correct. In diode test mode, the values \u200b\u200bare 500-1200mV.

In measurement mode, the values \u200b\u200bwill be similar to those in the figure. The one in the leftmost digit denotes exceeding the limit, or infinity.

Other ways to determine polarity

The easiest way to determine where the plus is at the LED is the batteries from the motherboard, size CR2032.

Its voltage is about 3 volts, which is quite enough to light the diode. Connect the LED, depending on its glow, you will determine the location of its terminals. This way you can check any diode. However, this is not very convenient.

You can assemble a simple probe for LEDs, and not only determine their polarity, but also the operating voltage.

If the LED is connected correctly, a current of about 5-6 milliamps will flow through it, which is safe for any LED. The voltmeter will show the voltage drop across the LED at this current. If the polarity of the LED and the probe matches, it will light up, and you will determine the pinout.

You need to know the operating voltage, since it differs depending on the type of LED and its color (red takes on less than 2 volts).

And the last method is shown in the photo below.

Turn on the Hfe mode on the tester, insert the LED into the connector for testing transistors, in the area marked as PNP, into holes E and C, with a long leg in E. This way you can check the performance of the LED and its pinout.

If the LED is made in a different form, for example, smd 5050, you can use this method simply - insert ordinary sewing needles into E and C, and touch them with the contacts of the LED.

Any lover of electronics, and even homemade products in general, needs to know how to determine the polarity of an LED and how to check them.

Be careful when choosing the elements of your circuit. In the best case, they will simply fail faster, and in the worst case, they will instantly burst into a blue flame.

Today it is not uncommon to see people throwing away computer power supplies. Well, or PSUs are just lying around, collecting dust.

But they can be used on the farm! In this article, I will tell you what voltages can be obtained at the output of a conventional computer power supply.

A small educational program about the voltages and currents of a computer power supply

First, safety precautions should not be neglected.

If at the output of the power supply we are dealing with voltages that are safe for health, then at the input and inside it there are 220 and 110 Volts! Therefore, observe safety precautions. And make sure no one else gets hurt by the experiments!

Secondly, we need a Voltmeter or multimeter. With it, you can measure voltages and determine the polarity of the voltage (find plus and minus).

Thirdly, you can find a sticker on the power supply unit, which will indicate the maximum current for which the power supply unit is designed for each voltage.

Subtract 10% from the written number just in case. This will give you the most accurate value (manufacturers often lie).

Fourthly, the ATX-type PC power supply unit is designed to generate constant supply voltages + 3.3V, + 5V, + 12V, -5V, -12V. Therefore, do not try to get an alternating voltage at the output, but we will expand the set of voltages by combining the nominal ones.

Well, have you learned? Then let's continue. It's time to decide on the connectors and voltages on their contacts.

Connectors and voltages of the computer power supply

Color coding of computer power supply voltages

As you may have noticed, the wires coming out of the power supply have a different color. It's not just that. Each color represents tension. Most manufacturers try to adhere to the same standard, but there are completely Chinese power supplies and the color may not match (which is why a multimeter will help).

In normal power supplies, the marking by wire colors is as follows:

• Black - common wire, "ground", GND
• White - minus 5V
• Blue - minus 12V
• Yellow - plus 12V
• Red - plus 5V
• Orange - plus 3.3V
• Green - power on (PS-ON)
• Gray - POWER-OK (POWERGOOD)
• Purple - 5VSB (power on duty).

AT and ATX power supply connector pinout

For your convenience, I have selected a number of pictures with pinouts of all types of power supply connectors for today.

First, let's study types and types of connectors (connectors) of a standard power supply.

The motherboard is powered by a 24-pin ATX connector or a 20-pin AT connector. It is also used to turn on the power supply.

MOLEX is used for hard drives, sidiroms, card readers and others.

A rarity today is a connector for flopy drives. But on old PSUs you can find.

A 4-pin CPU connector is used to power the processor. There are two of them or even double, that is, 8-pin, for powerful processors.

SATA connector - Replaces MOLEX connector. Used for the same purposes as MOLEX, but on newer devices.

PCI slots are most often used to supply additional power to various PCI express devices (most common for video cards).

Let's go directly to the pinout and labeling. Where are our cherished tensions? And here they are!

Another picture with pinout and color coding of voltages on the power supply connectors.

Below is the pinout of the AT type power supply.

Here you go. We figured out the pinout of computer power supplies! It's time to move on to how to get the required voltages from the power supply.

Receiving voltages from connectors of a computer power supply

Now that we know where to get the voltages, we will use the table I gave below. It should be used as follows: positive voltage + zero \u003d total.

It is important to remember that the current of the final voltage will be determined by the minimum value according to the ratings used to obtain it.

Also do not forget that for high currents it is advisable to use a thick wire.

The most important thing!!! The power supply is started by shorting the wires GND and PWR SW ... Works as long as these circuits are closed!

REMEMBER! Any experiments with electricity must be carried out with strict adherence to electrical safety rules !!!

Supplement on connectors. Clarification of the pinout of PCIe and EPS connectors.

Electric current, flowing through the LED in the forward direction, causes optical radiation. Its reverse inclusion in electrical circuit will not give such an effect and may even damage the LED. To avoid troubles in operation, this electronic component must be tested, that is, its polarity must be determined. The following methods for determining the output of the minus and plus are most often used for low-power emitting diodes in a package with a diameter of 3.5, 5.0, 10.0 mm.

Visual difference between anode and cathode leads

A new LED usually has two leads (legs), one of which is slightly longer than the other. The long lead is the anode. It is connected to the plus of the power supply. The short lead is the cathode, which is connected to the negative or common wire. Sometimes the cathode lead is marked with a dot or a small cut on the case. Soldered or used LED has short legs of the same length. In this case, it is necessary to determine where the plus and where the minus is by carefully examining the crystal through a plastic lens. The anode (plus) is distinguished by a much smaller contact size inside the lens compared to the cathode. The contact of the cathode (minus), in turn, resembles a flag on which the crystal is placed.

When repairing electronic units, you may come across light-emitting diodes with a non-standard pinout. The manufacturer can mark them from the side of the legs or make a thickening of one of the conclusions. Sometimes the pinout of such LEDs is not intuitively clear, and the special structure does not allow you to visually determine the polarity. In such cases, you will have to resort to electrical measurement.

Power supply polarity detection

For quick testing, you will need a current source with a voltage of 3 to 6 volts (battery or accumulator), a 300–470 Ohm resistor of any power and, directly, an LED. Due to the low value of the reverse voltage, it is not recommended to check the LED from a source with a voltage greater than 6 V. The resistor must be soldered to one of the legs and then touch the contacts of the power source. Touching the anode to the plus, and the cathode to the minus, a working emitting diode will glow. Repair shop workers often arm themselves with dead three-volt batteries from a computer motherboard or electronic wall clock (CR2032). After making sure that the current of such a battery does not exceed 30 mA, it is briefly inserted between the terminals of the LED without a resistor. Plus and minus are determined by its glow.

Checking with a multimeter

The multimeter is the little assistant of a real master. It is also called a tester for the fact that it can diagnose most electronic components, identify short circuits, and measure basic electrical parameters. Testing an LED with a multimeter provides the following benefits and determines:

• polarity (anode, cathode);
• glow color;
• suitability for use.

You can determine the polarity of an LED in one of three ways. In the first case, to carry out measurements, you need to set the tester switch to the "resistance test - 2 kOhm" position and briefly touch the leads with the test leads. When the red (plus) probe touches the anode, and the black (minus, connected to the multimeter's COM connector) touches the cathode, a number in the range 1600-1800 will flash on the screen. Such testing of a faulty semiconductor device will display only one on the screen. The disadvantage of this method is the absence of crystal exposure.

The second method involves setting the switch to the "continuity, diode test" position. Touching the red probe to the anode and black to the cathode, the LED will light up slightly. A number will be displayed on the screen, the value of which depends on the type and color of the emitting diode.
The third method eliminates the need for probes. To do this, the tester must have a compartment for testing PNP and NPN transistors. Fortunately, most models have this feature. To determine the polarity, you will need two sockets labeled E - emitter and C - collector. As you know, negative bias is applied to the collector of a PNP transistor. Therefore, during testing, the LED will light up if the cathode is inserted into the hole labeled "C", and the anode into the hole labeled "E" in the PNP compartment. Determining the polarity in the NPN compartment, the working LED will glow if the legs are reversed. This method is the fastest and most effective, and the glow reaches its maximum brightness. Other types of LEDs can be tested with the multimeter probes. For example, in the dialing mode, you can light up individual segments of the LED indicator. In addition to single-color LEDs, two-color and multi-color analogs are produced in a five-millimeter case. Moreover, they can have 2, 3 or 4 outputs. Two-lead two-color light-emitting diodes visually have a complex crystal shape. When the tester checks the plus and minus, they conduct current in both directions, but they glow different colors... Determining the polarity of a 3-pin or 4-pin LED is to find a common minus or plus, depending on the manufacturer. To do this, the terminals of the multimeter are sorted out and the crystal glow is recorded.