It is impossible to provide the required level of protection for a home, apartment or office space with a reliable lock and a metal door alone. To be sure that intruders will not enter the house without your invitation, we suggest installing a door opening sensor, which will warn about unexpected guests with a corresponding signal on the security alarm control panel. Not all doors have mortise locks - apartments also have windows, balconies, and in houses there is a “back” entrance, in offices there is an emergency exit, so it is impossible to keep all entrances under control, but an element of the smart home system will become a reliable assistant and ensure a comfortable level residence or work.
- The need for door sensors in the house
- Principle of operation
- Sensor device
- Sound alarm
- Be aware of all uninvited guests
- Reed switch for safety
- Advantages and disadvantages of reed sensors
- What are they used for in the home?
- Wireless door sensor
- Door alarm gsm
- Operating principle of sensors
- Criterias of choice
Reed switch for safety
The reed switch sensor is perhaps the most popular among all those that can be installed on the front door. These solutions are widespread in almost many industries, but they are also used in security systems. The advantage of a reed switch is that it is an affordable, easy-to-install and very effective sensor that responds to the opening of doors, gates, hatches, windows - any moving structures.
Previously, electromagnetic relays were used for these purposes, but these devices could not cope with the assigned tasks - their switching speed was too low. In addition, rubbing parts accelerated wear of the contacts, which led to relay failures. But after the creation of reed switches, the relays were forgotten.
Application
A magnetic contact-type door opening sensor or a reed switch can respond to the closing or opening of moving parts that provide access to the room. These broadcasters are located inside buildings, they are invisible to the eye, their operation is almost trouble-free - with the help of miniature sensors, reliable protection of remote objects is ensured.
With the help of such sensors, it becomes possible to organize an effective security system in an apartment or cottage, practically without major investments. You can install such a door opening sensor anywhere - on safes, store windows, inside apartments on steel doors.
GSM door alarm
There are also such devices on the market. They are seriously different from full-fledged wireless security alarms. This device is extremely simple, but at the same time it can reliably protect property.
The devices are a GSM door opening sensor - a special controller equipped with a GSM module. If the sensor is triggered, the controller will send an SMS to the home owner. This simple device can be installed almost anywhere there are two doors. The operation is based on the same reed relay.
To control this security device, manufacturers offer several SMS commands that allow you to turn the system off or on, set the object to security, and enter a number for sending SMS. Some models may have a mode for listening to what is happening, for example, in an apartment - this mode can also be launched using SMS commands.
In order to secure the alarm, the manufacturer has provided a special Velcro. This simplifies repeated installation/disassembly of the device. During installation, you need to carefully set the distance from the controller to the magnetic sensor - the alarm threshold is 10 mm.
As you can see, with the help of such door opening sensors you can reliably protect the front door and apartment, private cottage or any other object.
Advantages and disadvantages
Reed sensors have their advantages and disadvantages. The advantages include:
- There is no chatter in the contacts. This is true for those whose terminals are moistened with mercury.
- Compared to classic relays, the sensors are characterized by high response speed.
- The sensor is considered durable and is not susceptible to physical shock (for example, due to careless handling or falling).
- This type of sensor does not create noise.
- The contacts burn poorly because they are located in a vacuum or inert gas. This also applies to those cases where a short circuit with erosion occurs with the occurrence of a spark.
- The price is affordable for everyone, since refractory or precious metals are not used in production.
- Small size compared to classic relays.
Minuses:
- Compared to open contacts, they are a bit heavy.
- Response speed is limited.
- You need to create a magnetic field.
- There are cases when the contacts remain in a closed state and cannot be removed from it.
- External magnetic fields affect them.
Electromechanical lock
The most reliable option. But also the most complex and expensive.
It is highly advisable to order a door directly from production with an electric lock to make it easier for everyone. Or you can change the already installed lock on the finished door to an electromechanical one, but this is quite difficult in practice: you need to select the appropriate size and ensure the cable outlet. When asking for a door with an electric lock, many door manufacturers are stunned and do not understand what they want from them, but for more progressive ones this is not a problem. The classic electric lock model is the Finnish Abloy EL502. It looks like this:
Electromechanical lock Abloy EL502
Similar to a regular mechanical lock, but with a control cable coming out of it. For many locks, you can install a standard cylinder for opening with a key, or you can not install it, then the lock will not be visible from the outside at all, but you need to be completely confident in the reliability of the system.
To open the lock, you need to apply a short-term impulse of 12 or 24 volts to it - the door will open. In addition to the impulse to open, many locks also have feedback - the state of the lock, which is also convenient. It is necessary to clarify the required connection diagram for each lock; it may be that you do not need to apply a pulse to the lock, but, on the contrary, remove the power to open it.
Specifically, in the Abloy EL502 lock, the tongue is controlled by a solenoid (magnetic coil), which does not look very reliable. There are locks with motorized deadbolts, which look much more serious. There, the extension of the crossbars is controlled by an electric motor. But their cost is much higher. Take a look at Mottura XNova for example.
Electromechanical lock Mottura XNova
The lock shows large crossbars and a mushroom-shaped hole for the cylinder.
By the way, there are locks in which a small bolt is controlled electrically, while large ones come out only when the key is turned. Not a bad option if you plan to use a key to securely close it (when you are leaving for a long time).
It must be taken into account that a cable must be routed from the lock; it is usually mounted in a channel inside the door and, on the side of the hinges, comes out in a cable transition , which protects the cable from being pinched by the door. This is a metal spring hidden at the end of the door.
Transition cable Abloy EA280
If the electric lock is installed in an existing door without a channel for the cable, then you can try running the cable under the decorative trim on the inside of the door. You can also install a padlock on the inside of the door or even an electromagnetic lock, like on entrance doors, but this is extremely unsightly.
A device called a booster . This is a small board (about the size of a box of matches) that protects the lock from applying too long a pulse to it (the coil may burn out) and limits the voltage.
A cable with as many as 10 cores comes out of the Mottura Xnova lock. I will write down their purpose so that the capabilities of the lock are clear.
- White - earth
- Brown - close
- Green - battery powered
- Yellow - open
- Gray - door position output
- Pink - output, low battery voltage indicator
- Blue - output, error indicator
- Red - output, latch position indicator
- Black - output, bolt position indicator
- Purple - the lock opens, after which it will automatically close
Principle of operation
The reed switch is a sealed switch. Its contacts are made of a special ferromagnetic alloy.
The principle of operation is based on the use of interaction forces that act on two ferromagnetic bodies in a magnetic field. These forces cause the spring contacts to deform and move before they are connected - this is how the door close sensor works. When a magnetic field of a certain strength is created, the ends of the springs are attracted and closed. When the strength of the magnetic field decreases (the two parts of the sensor are separated), the springs are released and the contact is broken, resulting in an alarm.
A constant electrical signal is passed through the security alarm circuit - it passes through the door opening sensor. A constant magnetic field can also be used. According to the standard, the reed switch response threshold can be adjusted from 30 to 50 mm. If you open the door at a distance of 30 mm, the alarm panel will receive a signal that the contacts of the magnetic sensor are broken.
Structurally, these detectors are made in minimal sizes. The sensor consists of two magnetic relay blocks in a plastic case. The door opening sensor is covered with a double layer of insulation - this helps eliminate false alarms.
Wireless Solutions
Many people today are trying to use wireless technologies. This trend has also been noticed in security systems. The convenience of wireless alarms lies in the absence of wires. All elements of the system are connected via a special protocol to the system console.
The wireless door opening sensor is the same reed switch. The design consists of a communication module, which houses a reed relay with open contacts. The second part is a magnet that closes the relay contacts.
It is recommended to mount the radio transmitting module on the door frame, and the magnet directly on the door so that when the door is closed it is opposite the radio transmitting part and can close the contacts of the magnetic relay. The operating principle of this door closing sensor is based on a reed relay. When the doors open, the circuit is broken, the contacts open - an alarm signal is sent to the main module or the central GSM unit. An alarm can also be indicated by a light indicator. It will also inform you that it is time to replace the device’s batteries.
The gap at which this device will operate starts from 10 mm and can be up to 20 mm. The device operates at a frequency of 433 MHz, and its range is up to 150 m in line-of-sight mode in open space. This wireless door sensor is powered by a 12 V battery. This battery will last the device for two years of continuous operation.
This is a typical door open sensor. All devices have approximately the same technical characteristics. They should be selected based on the specific situation.
Internal workings of the door sensor
Although there are several different types of security door openers, most use a reed switch and a magnet to detect when the door is open or closed.
Reed switches are used in countless devices, from doorbells to laptops, and rely on a collection of electrical components. The switch closes when the two parts are close to each other, and when the two parts separate, it breaks the electrical circuit.
When you add a door sensor to your home security system, the device will come with both parts: a reed switch and a magnet. One element is attached to the door frame, and the other is parallel to the first element on the door leaf itself. The two parts create a closed loop when the door is closed. When the door opens, the magnet and switch are separated, breaking the circuit. When the circuit is broken, the central control panel records this fact and acts according to a given scenario.
Installation of door sensors
The door detector is easy to install. Using a good strong adhesive (or double-sided tape), attach one part of the sensor to the door and the other to the frame. In this case, the magnet is mounted on the door leaf, and the reed switch with connected wires (if the detector is wired) is on the frame, and the wires can be hidden behind the door slopes.
It is better to place the sensor closer to the edge of the door (on the opposite side from the hinges) and preferably at the very top to prevent accidental knocking down.
Correct installation of the door sensor
The two pieces should be mounted right next to each other, with a small gap between them. If they are too far apart or not parallel to each other, the parts will not be able to interact, resulting in the reed switch and magnet not interacting.
Garage door opener sensor
Although they are not as common as regular burglar alarms, garage door sensors can do a lot for your home security system. There are two ways to detect a garage door opening: with a standard door sensor or with a roller or overhead door sensor.
The standard sensor works the same as on any other door. Two parts are installed next to each other, one on the gate and the other on the wall next to the gate. When the garage door is raised or opened, the circuit opens and activates the alarm.
The angle sensor is slightly different. Instead of operating using two parts, such a sensor is a stand-alone device. They are designed to detect changes in angle. When the garage door is closed the sensor is vertical, when the door is opened the sensor moves up with the door and this change in angle will trigger the sensor to trigger the alarm.
Reader
How are we going to open the door? We will not consider Danalock and Utopic S, they have a lot of ways to open, including wireless remote controls, finger readers, code-keyboards and the same Bluetooth, Z-Wave and Apple HomeKit, but let’s consider the general option, when we have a separate “dumb” electric lock, the cable from which comes out of the door.
There are a huge number of solutions on the access control systems market. We will consider the most progressive ones - by fingerprint or veins of the palm or face.
By the way, regarding access via a smartphone via NFC. It should be kept in mind that only Android smartphones have this option. On the iPhone, NFC is used only for contactless payment, nothing else, this function is blocked by the system.
Of course, it is necessary to organize the system in such a way that the lock opening relay, turned on by the reader, is not located in the reader itself, as in most inexpensive systems. Otherwise, we could open the lock by removing the reader from the wall and shorting the lock wires. I personally really like the products of the Korean company Suprema, although they are quite expensive. There is a Russian company Biosmart that does similar things.
The Suprema Face Station reader allows you to open the door using facial recognition.
Suprema Face Station
It has two video cameras (to understand the depth of the picture) and a screen. When setting up, you need to turn your head, the reader remembers your face. I tried it and it works quite accurately. Recognizes a face even with a hat and glasses. It doesn't work with a photo of a face.
Suprema Bio Entry Fingerprint Reader:
Suprema Bio Entry
It works with fingerprints plus reading cards of different formats.
A separate Secure I/O device is installed inside the room; it is connected to the reader with an RS485 cable; it is needed to control the lock. That is, the door cannot be opened by knocking the reader off the wall and shorting any wires.
Suprema readers connect to a local network and are programmed remotely; to do this, you need to purchase a license for the Biostar program. Not cheap, but it will be possible to control readers and access rights of different users from an application on a smartphone. We also need a client program that will constantly work on the computer inside the house. In general, this is already a serious system. Or there is a free version of the application that allows you to configure one reader, but a license for it must be obtained through technical support and updated every 3 months.
An uninterruptible power supply must be provided for the equipment. It should be taken into account that, for example, Suprema Face Station has a power supply of 24 volts, and Secure I/O has 12 volts. Electromechanical locks also have different supply voltages, usually 12 or 24 volts, a current of 3 amperes, albeit for a short time. As uninterruptible power supplies, you can install simple Russian Poliservis or SKAT, or my favorite Meanwell for installation in a panel on a DIN rail with batteries at the bottom of the panel.
This is the circuit I designed to control a Mottura electric lock from a Suprema fingerprint reader. You can also open it from the Smart Home system application (Beckhoff controller).
There is an exit button to open the lock from the inside. The circuit uses a Mottura XNova lock, it needs to be constantly supplied with 12 volts, and it opens with a “dry contact” signal.
Application and installation features
Door sensor in working condition
Reed switch type sensors are installed on moving or fixed parts of controlled objects (doors, in particular) that provide access to the room. They guarantee reliable operation of security equipment when attempting to enter buildings. For the system to function properly, it will need to be supplied with electrical power from the local wire line.
By installing an extensive network of reed sensors, it is possible to organize a reliable security system throughout the house at a minimum cost. These elements can be installed anywhere - on the glass of shop windows, on the doors of safes, as well as inside apartments on the entrance doors. Features of their installation include their mandatory placement on the internal surfaces of objects. Advanced models of sensors provide for their activation with simultaneous notification via mobile phone.
Popular manufacturers
The REDMOND device is a high-tech device for the security of premises.
Among the well-known models of reed sensors used to monitor the condition of doors, the following samples stand out:
- wired magnetic devices used in security alarms of the PSM MC type;
- sensors for opening doors and windows, magnetic contact type COMK 1-3;
- wired magnetic contact device for doors/windows with security alarm system PST MC35;
- wireless reed switch door opening sensor (with support for 433 MHz broadcast frequency).
The “smart” reed sensor SkyGuard RG-G31S belongs to the same series. This miniature but technologically advanced device from REDMOND guarantees the impossibility of uncontrolled break-in and the safety of property in the house. Sensors are used to remotely monitor the status of doors and windows at the following facilities:
- in apartments of urban buildings;
- at country cottages;
- in garages remote from the house or adjacent to it.
In addition, they are used to monitor the condition of secret cabinets, secret drawers and safes.
The “smart” reed switch sensor from the manufacturer REDMOND works synchronously with the Ready for Sky Guard mobile application. If it detects any movements in the apartment accompanied by the opening of doors, it immediately sends an alert to the smartphone.
Main characteristics
The main task for such a security sensor is to clearly record the illegal entry of uninvited guests into the house. In addition to its main purpose, such devices usually have other very interesting functions. Thus, some models on the market have the rudiments of artificial intelligence and can tell the owner who entered the house or, for example, at what time the children returned from school. To activate such functionality, you will definitely need “smart” video surveillance capable of identifying someone entering the home.
When installing such a tiny sensor on an interior door, you can monitor whether an unauthorized person has visited a user-selected room, closet or safe. The sensor can be installed in any corner of the house - in the profile of a window, gate, on a refrigerator panel and even in a closet. This way you can control the situation at any time and prevent unwanted actions on the part of your minor household members.
In terms of their ergonomics and visual characteristics, such sensors are extremely similar to each other, regardless of the manufacturer. All of them have very modest sizes, which allows you to install such devices in the most secluded places in the house. Most modern models are presented in the format of a mini-device with magnetic properties (for installation on metal surfaces), operating via wireless technology. Wired sensors are also on the market today, although the demand for them is noticeably less than their wireless counterparts.
Manufacturers do not limit users in the choice of door sensors and offer a lot of variations with varied functionality. If you wish, you can choose a budget version of the sensor, which will only notify the homeowner about open doors through notifications sent to the application on the mobile device. If you have a sufficient budget, a full-fledged smart device is available that can independently open or close the door, as well as execute voice commands.
Varieties
The device operates on the principle of opening or closing the line transmitting electricity. The magnetic flux intensity determines the closed or open position. It is noteworthy that it does not matter where the magnetic field originates from. It can appear either from an electromagnet or a permanent magnet.
Magnetization in the device begins to occur when the power lines are affected. After this, the elastic force is overcome and attracts the contacts to each other. As a result, the circuit is closed.
The sensor will remain in this state as long as the magnetic field remains. After the influence of the power lines ceases, the contacts open. For the next short circuit to occur, the field around the device must be created again.
Based on this, experts consider the reed switch to be a switch.
Control from Smart Home
If we install a battery-powered electric lock drive with Z-Wave support, and our system is Z-Wave, then there are no difficulties, everything will work.
In the case of a separate electric lock, we need to connect a relay either to the output button connection contacts on the lock controller, or (for greater fault tolerance) place this relay in parallel with the lock's power circuit so that it supplies power to the lock. It is important to remember that you cannot supply power to an electromechanical lock for a long time, only about a few seconds, otherwise the lock may well burn out. Abloy and Cisa (and others) locks have a special module that limits the voltage and pulse time to protect the lock.
The conclusion is this: there is a simple way and a difficult way. Simple - install a cylinder with a Danalock drive or an equivalent into the existing lock and use the opening means provided by the manufacturer. Complex - we install a separate lock, a separate reader, a separate controller, a separate uninterruptible power supply with batteries.
For the second option, you need to think in advance about the connection diagram for all devices and options for opening the lock. For example, the Suprema reader and the electromechanical lock require connection to different power sources, both need to be backed up with batteries. The Secure I/O device has a rather weak built-in relay; you cannot connect a lock to it; you need a separate relay. If the lock, in addition to the reader, is controlled by a smart home controller or GSM controller, then you need to connect the relay controlled by them in parallel with the reader relay so that the systems work independently.
Recommendations for protection
If you connect a reed sensor with your own hands, then you need to consider the following points:
- It is necessary to install the thinnest metal plate. It is placed between the magnet and the reed sensor for protection.
- Magnetic and reed switch sensors must be installed so that they are directed towards each other. The distance should be short.
Sources
- https://o-dveryah.ru/bezopasnost/datchik-otkrytiya/
- https://ProDatchik.ru/vidy/datchik-gerkonovyj/
- https://zen.yandex.ru/media/id/5e2b8252fe289100b035d7f2/kak-rabotaet-datchik-otkrytiia-dveri-5e564b1ab3a4f601750bcb59
- https://StrojDvor.ru/umnyj-dom/preimushhestva-ispolzovaniya-datchikov-otkrytiya-dverej/
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