How to short-circuit a phone and why it is needed. Normally open and closed contacts What does it mean to close contacts
Normally open contact(no contact, NO) – a term describing the state of the main or additional contacts of a starter, button, relay, contactor that have two opposite states. In operating condition, the normally open contact is closed, and in non-operating condition, it is open.
Normally closed contact(break contact, NC) - similar to normally open, but symmetrically opposite. In the working state, the contacts are open, and in the non-working state, on the contrary, they are closed.
Block contacts
Block contacts- This electromechanical devices used for switching control and signaling circuits.
Typically, such devices have from 1 to 4 normally open or closed contacts. They are installed on the side or front of the starter (contactor).
NC – contacts used mainly in interlocking circuits (see example below). But in addition to blocking circuits, they can also be used to connect an autonomous power supply or alarm system.
NO – contacts used for signaling, for example, when the contactor is turned on, it is triggered and supplies voltage to the signal lamp, or a control signal to the controller/control station.
Electrical contactor interlock
Let's look at an example of how a contactor is electrically blocked using additional contacts.
When voltage is applied to the coil terminals of the contactor K 1, it operates together with its block contact K 1.1. The normally closed contact K 1.1 opens, interrupting the power supply to the coil of contactor K 2. A similar process occurs when contactor K 2 is turned on.
This electrical contact interlocking circuit prevents the simultaneous activation of two contactors at the same time. This connection of contactors is often used when connecting an asynchronous motor. Normally open contacts are not used in this circuit, but can be used in control and signaling circuits.
Those who have computers for a long time often complain about some problems. One of them is a malfunction of the power button. From time to time they fail completely, and then the question becomes relevant: how to turn on the computer without a power button?
general information
It also happens that there is power in the network, the motherboard signals about operation with its LED, but when you press the power button, nothing happens. The computer simply won't turn on! What to do in this case? How to turn on a computer without a power button, preferably in a not very difficult way?
It should be noted that there can be an extremely large number of reasons for this behavior of technology. Within the framework of the article, several of the most popular failure options and their elimination will be considered. Those that can easily be repeated at home will be given. If none of the things presented below can help, then it would be better to turn to professionals so that they can fix the problem.
Fast but complex check
First you need to check the functionality of the power supply:
- To do this, you must first disconnect all connectors (from the video card, motherboard, hard drives, cooler, etc.).
- You need to connect two wires to the widest connector on the power supply. As a rule, it is green and the nearest black. You can do this using a regular paper clip or tweezers.
- We supply voltage from the outlet. And if the fans do not work, but everything was done correctly, then we can confidently say that the fault is in the power supply. If they start, then we can state that it is working.
Now you can connect the connectors back and solve the next problem.
How to start a computer?
So, we found out that the problem is in the computer itself. What to do now? The motherboard has many connectors to which elements of the front panel of the computer case are connected - buttons, LEDs, USB ports and other components. The connectors for the power button are usually located on the lower right side of the board. But it would be best to open the documentation for the element you are using and figure out where its contacts are. If it is not there, then you need to find the inscriptions: “On-Off” on English language(Power Switch (PW Switch), Power ON, On-Off). After this, remove the connectors and carefully close the PWR SW and Ground contacts. How? Yes, even with a ballpoint pen.
Here's how to turn on your computer without a power button. And if everything works after that, then we know exactly what the problem is. It is in the on/off button itself. But what to do after finding out this fact? Of course, repair or replace it. You can temporarily get out of the situation using the reset button by connecting it instead of the broken one. It is usually signed Reset.
In this simple way you can make the equipment work. And if the power button is broken, we can recommend fixing it as soon as possible to avoid this problem. But be careful - with inexperience or connivance, the computer can be seriously damaged. Therefore, you should carry out full repairs only at your own peril and risk. Fortunately, you can use the reset button for a very long time.
Working with keyboard shortcuts
The keyboard is a part of the computer that is very underestimated. Perhaps, answering the question of how to turn on a computer without a power button, you should have started with this method, which is both simple and easy.
To do this, we will have to work with the basic input/output system. True, not everything is so easy here. The point is that for successful use this method the keyboard should not be connected to a USB port, but to a round PS/2. If this is not so, then, alas, nothing will work.
If the keyboard is what we need, then we need to set the setting (namely, select the items that correspond to the buttons that can turn on the computer using the keyboard). It could be either Space Bar (spacebar), or Power Key (the power button found on “advanced” keyboards) or Ctrl-Esc. After this, you should save the settings and turn off the computer to try this innovation.
How to find the required property? As soon as you have logged in basic system I/O, you should go to the Power Management Setup section and change On by Keyboard. And here we have an illustration to the question of whether it is possible to turn on the computer without a power button.
Features of technical design
As one person said, the only thing more reliable than the power button is a Soviet-made cast iron frying pan. And well, it should be noted that there is a significant amount of truth in these words. Therefore, if there is a button, then you can think about whether it’s worth changing the piece of equipment? After all, this is one of the most basic elements PC, so when it fails, we can say that the exploitation is literally off the charts. Or they bought clandestine equipment from China. To prevent this from happening, you need to be careful when choosing a computer when purchasing it.
Safety precautions
And now I would like to go back a little and talk about safety precautions. It should be noted that most computer elements operate under low voltage, which amounts to a few or even fractions of volts. But not everything is so simple - because otherwise it would not be connected to a 220 V network. Therefore, always, even with the smallest cosmetic changes, it is necessary to completely disconnect the equipment from any voltage supply. Of course, this is quite labor-intensive, but remember that all safety precautions are written in someone’s blood.
Let's look at a small example of neglect. Here is a computer with system unit It is very difficult to completely disconnect from the power supply. It is put into sleep mode and the side panel opens. And then an interruption is triggered (for example, from a message that came over the network) and the equipment turns on. It's unlikely to give you an electric shock, but the fan is on motherboard may pass well through the hands. He, of course, won’t cut off your fingers, but he can beat them noticeably with his blades.
Conclusion
So we sorted it out, but these were the most primitive ways of checking the status and activation. It should be noted that there are quite a few a large number of various auxiliary equipment with which you can restore and start literally dead electronics. But, as a rule, it is available to experienced professionals who have been engaged in this business for quite a long time.
Although, as previously mentioned, in case of such a breakdown it is still better to think about replacing the system unit. Indeed, in this case, you can remove all the “internals” from it and rearrange it into a new one. And this will allow you to preserve all existing developments, and the replacement will be forgotten in a few days.
The system case is an important component of the entire computer. It is in the case that the “production workshop” of the entire computer is located, so to speak. It is in the case that the motherboard is installed, and it is already “hung” on it RAM, video card, processor and all kinds of wires and cables. Moreover, the power supply is located in a separate place inside the case, as well as HDD and drive.Modern cases look quite attractive, menacing, aggressive, unusual... The developers have enough imagination, which means that ordinary buyers can choose from a huge assortment. But not only do the current buildings have an attractive appearance, they also have “working” advantages. Such advantages are the USB connectors, as well as microphone and headphone connectors on the front of the case, which in turn means that we don’t need to crawl under the table and get to the back panel of the case every time we need to connect a flash drive. I think everyone will agree that these are, in principle, trifles, but still, it’s more pleasant to just insert a flash drive in front and start working.
But, unfortunately, there are cases when some parts of the computer case fail. We are talking about the notorious POWER button, which is available on absolutely every case. Over the course of long-term use, this button may simply fail, for example, stop pressing or, on the contrary, sink deep into the case, and no matter how hard you try, you won’t be able to turn on the computer. What to do in such situations? If you don’t really need a computer, then it’s better to call a repairman and wait with peace of mind until he repairs everything, paying him a certain amount of money for it.
If you need to use the computer quite urgently, then perhaps you should use the following advice.
First, you need to find a flat surface and carefully place the system unit so that the left cover is facing you, while you should not disconnect all the wires in order to complete everything faster, but you should make sure that these wires are not strained. In addition, a prerequisite must be that the computer is disconnected from the power supply, as they say, you never know. Next, what needs to be done is to remove the left housing cover. In modern cases, this usually does not require any great effort, so this should not be a problem.
After removing the cover, a stunning picture will appear in front of you. You will see everything that at one time you paid a round sum for, and that usually works peacefully, making an innocent noise, and that which now does not want to “start up”. Our attention should be primarily focused on the multi-colored wires that run from the front of the case to the motherboard. There can be a lot of such wiring, and it’s not surprising, because there are also connected POWER buttons And RESET button, And USB ports, together with audio outputs. So, at the next step, we may need a little knowledge of English, which many received at school, because on the wiring themselves, as well as on the motherboard, near the connection of these wiring, it should be written what they mean. For example, you can take USB ports. On the motherboard itself, near the connection, there should be an inscription USB1, USB2, etc. This means that the wires connected to these connectors are nothing more than USB connection ports.
But we shouldn’t forget about our problem, and this means that we need to look for POWER postings(usually these are two wires woven together). Typically, the connectors to which the power or reset buttons are connected are located on the lower right side of the motherboard:
On most motherboards, these connectors are the same and consist of 9 pins arranged in two rows. Two last contact in a short row of 4 plugs are responsible for turning the computer on/off.
Here are connector diagrams for the most popular motherboard manufacturers.
MSI
AsRock
Asus
Biostar
Epox
Foxconn
Gigabyte
Intel
Once these two wires have been found, you should find where they are connected to the motherboard. Once the connection location has been discovered, it is worth carefully disconnecting these wires so that the small plugs are exposed.
That's it, now we're almost done. The final step is to turn on the computer; for this we need an ordinary stationery pen, preferably one that writes boldly. Once you have found such a pen, you can connect your computer to the power supply, and then carefully run the tip of the rod over these exposed needles. Or in other words, you just need to close these contacts. After these steps, the computer should come to life and the download will begin. If nothing happens, then you should repeat the procedure, but close these needles quickly enough.
Thanks to these simple steps, you can start the computer without any problems, but this should not be neglected, and it is better to quickly repair the start button on the case to avoid unnecessary problems.
Attention: Neither the author of this article nor the administration of this site bears any responsibility for possible problems that may occur when turning on the computer in this way. You will perform all of the above actions at your own peril and risk, and will be solely responsible for possible problems that are not described in this article.
In everyday life, we often come across switches. These are all kinds of switches, buttons, toggle switches - they allow you to control devices discretely, in other words, turn them on and off. A regular switch has two contacts that can be closed or opened. electrical circuit. Discrete control various devices V automatic mode assumes the ability to turn them on and off without human intervention. It is for this purpose that an electromagnetic relay is intended, and that is why not a single automatic control system can do without it.
Electromagnetic relay– a device that has a group of contacts that change their state to the opposite when a control voltage is applied.
Rice. 1. Electromagnetic relay
In simple words, a relay is a switch that is turned off not manually by a person, but electrically, by applying a control signal. To make it completely clear, let’s consider the principle of operation of an electromagnetic relay.
Relay operating principle
A relay consists of a coil, an armature and a group of contacts.
1 – relay contact conductors, 2 – relay contacts, 3 – armature, 4 – core, 5 – coil
The principle of operation of the relay is extremely simple. If you apply a control voltage to the coil, a magnetic field will arise in it and attract the armature, which in turn will close the contacts. In Fig. 2 shows a relay with one group of contacts, but in general case There can be many contact groups. When a magnetic field appears in the coil, they all change their position to the opposite. Yes Yes! Exactly the opposite. This means that initially they can be not only open, but also closed.
Normally closed and normally open contact
There are two main types of relay contacts: normally closed (NC) And normally open (NO) . The names reflect the "normal" state of the contacts when there is NO voltage across the relay coil. Fine closed contacts are closed in the normal state, and normally open are open.
Another type of contact - changeover. They can be called neither normally closed nor normally open, since they have both contacts. When a relay is switched, such a contact opens one circuit and closes another. This will become clearer when we look at their graphic designation in the diagram.
Designation
On electrical diagrams relays are designated as several separate elements:
The conditional division into different elements is introduced solely for convenience. This allows the coil and contacts to be placed in different parts diagram to make it more compact and readable. In this case, all elements of one relay are designated by the same letter code, because structurally it is one element.
Also, for convenience, some relay elements can be shown together in the diagram. For example, a group of normally open contacts can be designated this way:
Examples
Example 1. Let’s draw a diagram that implements the following algorithm: if the pump is on, the green light is on, and if it’s off, the red light is on.
At the moment when the pump turns on, the limit switch closes inside it (normally open contact), which we introduced into our diagram. At the same time, voltage “comes” to the coil of relay K1 - the relay is activated, opening the NC contact K1.1, and the red light goes out. At the same time, when the contact inside the pump closes, the green light comes on.
Example 2. Let's implement example 1 using a relay changeover contact.
In this circuit, relay contact K1.1 is a changeover contact. When the relay is in the “normal” state, the red lamp is on. When triggered, relay K1.1 changes its state and the green lamp lights up.
Auxiliary contacts in electrical engineering - normally open and closed or normally open and normally closed, respectively
Definitions
Auxiliary contacts- contacts of switching devices operating auxiliary circuits that are not electrically connected to the main circuit and control circuit. Auxiliary contacts are kinematically connected to the main ones and reflect their switching position (closed or open).
Main circuit- the electrical system that the device closes and opens. Control circuit- an electrical system with the help of which the device changes its switching position.
Types of auxiliary contacts
Normally closed contact- a contact that is closed when the main contacts are brought together and open when the main contacts are apart (corresponding to the current position of the main contacts). That is, in the off position the closing contact does not pass electricity.
Normally closed contact- a contact that is open when the main contacts are brought together and closed when the main contacts are apart (reverse correspondence). When the device is turned on, no electric current flows.
Such contact groups are used on red stop buttons. When you press the Stop button, the control circuit is broken and the engine stops.
Meets definitions 2.3.13 and 2.3.14 normative document GOST 50030 part 1.
Compliance and designation
Contact Matching:
- closed = normally open = normally open = n ormal o pen;
- p opener = normally closed = normally closed = n ormal c lost.
Considering the first and last formulations, stand for:
- 1з = 1NO;
- 1p = 1NC.
The number means quantity auxiliary contacts. hence the markings:
- two pieces - 2з = 2NO;
- three pieces - 3p = 3NC;
- four pieces - 4з = 4NO;
- two closing and two breaking - 2з+2р = 2NO+2NC.
Think of the “=” sign as an “or” conjunction.
Additional Information: types of contact elements and their designation according to GOST 50030 part 5.1.
Photos
| The first photo shows a PM12 starter manufactured by EKF. The second photo shows the bridge-type auxiliary contacts:
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The first photo shows the KT 6023 crane contactor. The second photo shows alternating auxiliary contacts (from top to bottom):
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