You can charge modern mobile gadgets not only from the network, but also from other devices - computers and laptops via a USB port. The output power of a USB 2.0 port according to generally accepted standards is 500 mA, the USB 3.0 port is 900 mA maximum at a voltage of 5 volts. Of course, this does not mean that the port will output the same power in all cases. It all depends on what device is connected to it. Smartphones can consume 500 mA, flash drives - 300 mA, simple mice - 100 mA.

According to the rules, this information must be indicated directly on the body of the USB device or in the technical documentation attached to it. But what if the data on the case is not indicated, and the documentation is not at hand, how then can you find out the power consumption? Very simple. Use USBDeview, a free utility from the developer NirSoft. It is very simple, informative and convenient. The utility does not require installation. Before starting it, connect the device you are testing to a USB port, preferably version 3.0, but also USB 2.0 if there is no other option.

Once launched, USBDeview will display a list of all USB devices, including ports. It is easy to identify active ones, that is, those to which external devices are connected - they are marked with a green flag.

To get detailed information about the device you are interested in, double-click on it and find the “Power” field in the window that opens. It will indicate the power consumed by the device in mA.

In addition to the current strength, the utility shows a lot of other useful information - device type, last connection time, driver name. USBDeview can also disconnect USB devices; perhaps this function will also be useful to you.

Developer page: www.nirsoft.net/utils/usb_devices_view.html

How to Avoid USB Port Damage

Often laptop manufacturers, and then the sellers who sell these products, give a decent warranty on the hardware they offer, with just one caveat: the warranty does not apply to USB ports. Why? Presumably, because this is the most vulnerable spot of the computer, and inexperienced users, of whom the majority are, can easily damage it as a result of improper use of the USB interface. Of course, developers are struggling with this problem and using different protective measures in different laptop models. But until the problem is finally resolved and in order to avoid trouble, users are advised to adhere to certain rules. The same applies to desktop computers.

All failures of using a USB port can be divided into software and hardware, that is, physical. Software failures are easier to fix. At least they will not require material costs, although they may take quite some time. In this case, it may be necessary to update or select a driver, configure the BIOS, and in difficult cases, reinstall the operating system. Physical malfunctions will require disassembling the computer, searching for and replacing burnt out parts, and the most unpleasant thing is replacing an expensive controller chip, which only a service center specialist can handle.

USB Energy Parameters

The most common option today is USB 2.0 connectors built into computer equipment. Less common are USB 1.1 versions, which began the widespread introduction of this type of interface at the end of the last century. The more advanced USB 2.0 began to be used in 2000; starting in 2008, USB 3.0 was released. Let's consider only the energy parameters of common ports.

The USB version 2.0 port, like the newer version 3.0, has special contacts that output a voltage of 5 V. This voltage is usually used to power external devices connected to the computer, controlled through the port, and also as a DC power source. Such a source can power a USB flashlight, a small audio system, or serve to charge a mobile phone battery.

However, the port's energy capabilities are not unlimited. The standard current it can provide is as follows. For a USB 2.0 port, the output current cannot exceed 500 mA, for a USB 3.0 version - 900 mA. When a slight overload occurs, it leads to a voltage sag, which can cause the connected device to malfunction. If the overload increases, the voltage decreases even more. In this case, there is no need to talk about the operation of the device, and the port itself may fail as a result of severe overheating of the circuit elements. Moreover, irreparable harm can be caused by a short circuit of the power buses, which will cause the burnout of the port’s protective elements.

What and how to connect to the USB 2.0 connector

Each computer can have from 2 to 6 USB ports installed, and even more on special order. Anything connected to each should not draw more than 500 mA of current. This guarantees the normal operation of the devices and the preservation of the functionality of the port itself. Low-power and serviceable loads, such as flash drives, a mouse, a keyboard or a web camera, cannot harm the interface. Powerful loads should be treated with care.

An example of a powerful load would be an external hard drive and other devices with a current consumption of 500 milliamps or more. Often such devices are equipped with two connectors connected in parallel in order to use two different USB 2.0 ports to connect them. The load capacity of this power supply method will increase to 1000 mA. Sometimes an external device has its own power source, then the port's electrical energy is not consumed at all, and it will function in a lightweight mode.

Everything that was said here regarding the USB 2.0 port is also true for its 3.0 version, with the only difference being that instead of a maximum load current of 500 mA, it has a limit of 900 mA.

Errors when connecting powerful loads

One of the mistakes is as follows. Let's say the connected device (external hard drive) has two paired USB connectors. One of them is the main one, having a power line and a data line, the other is additional, equipped only with conductors for power. Often, due to inexperience or forgetfulness, the consumer can use only one main connector, leaving the additional connector unconnected. If the device draws 800 mA current, it will overload the USB 2.0 port, causing it to fail.

A similar situation can arise when the user uses a passive USB interface splitter - a device that increases the number of USB sockets. Such a device is designed to connect an appropriate number of low-power loads and cannot in any way increase the maximum current of the source port. If the consumer did not understand this and caused an overload through powerful loads, then trouble should be expected.

Consequences of port failure due to overload

To prevent an overload or short circuit of the power supply bus of the USB port from leading to more serious damage to the computer, developers build in special protection measures. For example, a fuse, a current limiting resistor, a self-resetting fuse. In each case, the consequences may be different.

If the fuse blows, the power supply to the port is turned off and it becomes inoperable. When a limiting resistor (usually an SMD chip) is overloaded, it becomes very hot, part of its resistive layer burns out, causing the resistance to increase, and therefore the load current decreases even more. Such a “fried” port will only be able to function with low-power loads.

If a self-resetting fuse is built into the circuit, then after removing the excessive load, the functionality of the port will be automatically restored. In other cases, you will need to disassemble the computer and replace failed elements.

Let us remind you that Serty-Service specialists are ready to help

if you have problems with USB devices.

After reading many sources, I found the same information everywhere: the USB 2.0 port is capable of delivering no more than 500mA, providing power of no more than 2.5W. However, some things cast doubt on this.

First of all, about useful things. If you select the “USB Root Hub” properties in the device manager (I don’t remember how it is in Russian, look at all devices), then the second tab “Power” will display information about the connected device: how many milliamps it requires. The value is taken from the filling of the connected device, this is not the actual current consumption:
- some flash drives require 500mA (Kingston, Transcend), and some require 200mA (Toshiba). Moreover, it has been experimentally proven that a Toshiba flash drive works on any 1.8 meter USB extension cable, even those not made to the standard. It turns out that the less a device consumes, the more chances it has to make money on a USB extension cable or low-quality front connectors of the case;
- and indeed: an optical mouse that consumes...

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Gambrinus
unregistered

Gambrinus

There is a reader. Sold without charger. How many amperes input is not indicated on it. Mini USB.

When charging Handy, the reader is charged by 20%, no matter how long it sits on charge. Handy charger: 5V, 1A.
-from USB-Hub the same.
-directly via USB-Anschluss from a computer/laptop (without USB-hub) charges 100%. Those. what comes out of the USB computer/laptop is suitable for the reader.

How many amperes are there from the computer? You need a charger with the same characteristics from the mains.

Freib
unregistered

Wiki
USB allows you to connect peripheral devices without its own power source (the maximum current consumed by the device via the USB bus power lines should not exceed 500 mA, for USB 3.0 - 900 mA).

Rosarote Ferkel
unregistered

Rosarote Ferkel

0 0

21.08.14 - 18:30

Good day! I'm not good with electronics! Got a question. There is an LED flashlight that is powered by 3 AA batteries of 1.5 V... Total 4.5 V. The USB port outputs a voltage of ~5V. I would like to make a flashlight with a USB tail, which could work on any computer (portable)...
.... The question itself. One electronics engineer told me that, in principle, on USB, pin 4 is plus, pin 1 is ground, but it is unknown how much current USB can pull... and there is an option that with my flashlight I will burn the port on the computer.
....Tell...

_fvadim

1 - 21.08.14 - 18:32

2 - 21.08.14 - 18:33

can be bought for 100 re on a flexible leg factory

3 - 21.08.14 - 18:35

(1) (2) do you know what current USB draws?...
...on a factory foot??? ... like there are already such flashlights, but I’m reinventing the wheel? Neg

4 - 21.08.14 - 18:36

(3) press the letter I on the right Neg

5 - 21.08.14 - 18:38

"5 (five) volts....

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The USB port is a universal serial bus. As you might guess, data is transferred serially through the USB port.

In the second version of USB, data is transmitted over two wires - twisted pair. The data in these wires is always of opposite polarity. Those. if the first wire is 0, then the second is 1. This method of data transmission allows you to achieve fairly high reliability at high speed.

At a given time, only one device can transmit - this is a property of any bus. Two more bus wires are used for 5 volt power. In total, the USB 2.0 port has 4 contacts: two signal and two power.

For the USB 2.0 standard, the maximum data transfer rate is 480 MBit/s. This amounts to approximately 48 megabytes per second.

Computer USB port voltage

There is a voltage of 5 volts at the extreme contacts of the computer’s USB port, which is used to power external devices. USB port current is limited to 500 mA for USB...

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Hello! I have selected topics for you with answers to the question: Is it possible to supply 12 volts to USB? (Motherboards):

USB 10 volt - Computer hardware
What happens if you connect 2 USB plugs in series and connect them to a laptop? Will there be 10 volts at the output?

Lan to USB Input, is this possible? - Computer hardware
To the core of the problem: All USBs on the laptop were knocked out by lightning, but at least one is needed. Replacing the motherboard is not an option for money, a new laptop...

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I’m not sure that I’m applying to the right place, I don’t have deep knowledge in the field of programming in Assembly language. But nevertheless there is a task and...

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Asus k50av does not turn on after shorting the 5 volt USB port to ground (the connector is broken) from the power supply to the motherboard, it comes out that...

Shadows on the screen and AIDA64 shows in...

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Once again about the electronic cigarette

An electronic cigarette is an innovative invention that helps maintain health for those who are unable to give up smoking. People with a strong will can also try to give up this bad habit through an e-cigarette. However... Read more

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Is it possible...

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You see, any gadget you want to get costs something. Not money, no (although that too), but millivolts subtracted from +5 Volts.

For example, to measure current consumption, you need to pass it through a resistance and measure the voltage drop. Exactly by this amount of voltage drop you will lose voltage across the load. It’s impossible to lower than 100mV, but at maximum currents it’s realistically 200-300 and up to 500mV.

For example, to disconnect and connect the load you need to install a transistor switch, and this is an additional about 100 mV minimum drop on the open switch.

And if you want to supply the load with the required current and no more, then you need all this together, and some extra in reserve.

There is also a voltage drop on the wires.

In fact, I have seen on some motherboards that there is a stupid limiting resistor on the +5V USB contact. For everything not...

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After reading many sources, I found the same information everywhere: the USB 2.0 port is capable of delivering no more than 500mA, providing power of no more than 2.5W. However, some things cast doubt on this.

First of all, about useful things. If you select the “USB Root Hub” properties in the device manager (I don’t remember how it is in Russian, look at all devices), then the second tab “Power” will display information about the connected device: how many milliamps it requires. The value is taken from the filling of the connected device, this is not the actual current consumption:
- some flash drives require 500mA (Kingston, Transcend), and some require 200mA (Toshiba). Moreover, it has been experimentally proven that a Toshiba flash drive works on any 1.8 meter USB extension cable, even those not made to the standard. It turns out that the less a device consumes, the more chances it has to make money on a USB extension cable or low-quality front connectors of the case;
- and indeed: an optical mouse that consumes 100mA works without problems on a 3-meter USB extension cable (and all the flash drives there are already “bye-bye”);
- the USB A-B cable going to the printer reflected the recommended value of 98mA;
- USB-HDD "Silicon Power" 320GB showed a value of 2mA (connected to one USB port and functioning successfully). The reason was found out: only 1 byte is allocated for the value of milliamps in the OS, and the maximum value of this counter is 255. Each counter value is equal to 2mA. This means that the USB-HDD has gone beyond the possible maximum number, and the counter has reset to zero +1 (corresponding to the number 514mA or 1026mA). But this is more than the 500mA stated in the standard!

This was the first doubt about the truth of I max = 500mA for the USB port.
Second: one hub serves several USB ports at once, and it is written that the maximum is 500mA per port. This means, in my case, the hub is capable of delivering 2.5A (since it is responsible for 5 ports). If it is capable of delivering a total of 2.5A, what should stop it from issuing, for example, 2.5A to one port, and simply blocking 4 others.
Third: the power supply data of the disassembled USB-HDD is 5V/0.85A. This is already more than 0.5mA. Moreover, it was experimentally found that starting the HDD (reactive load) requires much more current than indicated on the HDD.
Fourth: I powered the router via a USB cable, and even then I somehow knew about the value of 1200mA. Here it is, the struggle of paradigms: heard there, seen here, said there, written here...

All the prerequisites for the experiment are there to obtain real numbers of current strength of this HDD. Over the course of a month, I will crash into the USB A-miniB cable with a high-precision ammeter for 20,000 rubles - and take readings from it. With your eyes or telemetry - whatever happens.

(added 04/07/2015): The experiment with the USB connector was successful, and my guesses were confirmed. The following equipment was used:
- multimeter DT838 (here’s a “high-precision” one for you...);
- active load: external HDD Samsung Momentus ST320LM001, USB coffee heater Orient W1002B;
- passive load: 4 resistors C5-16V-8W 1Ohm ±1%;
- USB plug;
- EliteGroup G31T-M7 and Gigabyte C51-MCP51 motherboards.

In the process of connecting the active load separately and in parallel, it became known:
- the maximum current for HDD (0.85A) is extremely accurate, it was obtained when spinning up the disk and during its initialization after loading Windows (fractions of a second). Current in idle mode: 0.28-0.35A, in transfer mode at a speed of 28MB/s: 0.56-0.63A;
- the heater consumes a constant 0.6A, including during start-up: there is no reactive load. A coffee warmer with a power of only 3W cannot be considered a serious household item;
- when connecting the load in parallel, it was possible to obtain a value of 1.19A. This value exceeds that stated in the USB 2.0 standard by 2.38 times.

Then the question arose: what is the correct limit? An inexperienced technician caused a short circuit when I entrusted him with the issue of soldering, but the equipment was not damaged, and the short circuit was not in vain: the ammeter recorded a constant passage of 3.3A through it, which means there is some kind of ampere limiter in the motherboard (for example, in the controller). Moreover, the restriction also worked when the PC was turned off.

To avoid damaging the active load, it was decided to abandon it in favor of a passive one, which transfers all the energy into its own heating: resistors. Oddly enough, high-power and low-resistance resistors were in short supply, and only 4 were found. Moreover, they are 25-30 years old, and the shelf life of this type is 15 years. What a surprise it was when, after finishing the experiments, it turned out that the resistance of one of them increased by +50%, to 1.5 Ohm. Then all the “errors” in the experiment became clear.

First, 1.45A was obtained, which successfully heated the resistors for several minutes. Further, lowering the resistance, a current value of 3.05A was achieved. And it was at this value that the automation (motherboard or Windows?) disconnected the USB connector, but in some unusual way: by reducing the current value not to 0, but to 0.4A.

So, the current limit for the USB connector is in the range )