reed switch(short for sealed magnetic contact) - an electromechanical device, which is a pair of ferromagnetic contacts sealed in a sealed glass flask. When a permanent magnet is brought to the reed switch or the electromagnet is turned on, the contacts close. Reed switches are used as proximity switches, proximity sensors, etc.
A reed switch with an electromagnetic coil constitutes a reed relay.
There are also reed switches that open the circuit when a magnetic field occurs and there are reed switches with a switching group of contacts.
Reed switches also differ in design features. They are dry (with dry contacts) and mercury, in which a drop of mercury wets the contact surfaces, reducing them. electrical resistance and preventing vibration of the plates during operation.
Options
Actuation magnetomotive force- the value of the magnetic field strength at which the reed switch contacts close.
Release magnetomotive force- the value of the magnetic field strength at which the reed switch contacts open.
Insulation resistance- electrical resistance of the gap between the cores (in the open state).
Contact junction resistance- resistance of the contact area, which is formed when the cores are closed.
Breakdown voltage- the voltage at which the reed switch breaks down.
Response time- the time between the moment of application of the control magnetic field, and the moment of the last physical closing of the electrical circuit by the reed switch.
Release time- the time between the moment of removal of the magnetic field applied to the reed switch, and the moment of the last physical opening of the electrical circuit by the reed switch.
Capacity- electric capacitance between the terminals of the reed switch in the open state.
Maximum number of operations- the number of operations at which all the main parameters of the reed switch remain within acceptable limits.
Max Power- the maximum power switched by the reed switch.
Switched voltage
Switching current
Advantages
- The contacts of the reed switch are in a vacuum or in an inert gas and do not burn, even if a spark occurs between the contacts when closing or opening.
- Durability of reed switches. It is believed that if you do not beat the reed switch and do not pass very large currents, then the service life of the reed switch is infinite (although the technical data for reed switches indicate restrictions, 108 - 109 or more operations).
- There is practically no bounce when turning on and off, there is no “pressing uncertainty”. The reed switch can have only two clear states - on and off.
- Smaller size compared to a classic relay designed for the same current.
- No need to use refractory and precious metals for contacts.
- Reed switches are almost silent.
- High performance.
Flaws
- High cost and greater weight compared to open contacts.
- The need to create a magnetic field.
- Difficulty of installation.
- Fragility. Cannot be used in environments with strong vibrations and shock loads.
- Limited actuation speed
Application
- Keyboards - keyboard synthesizers and computers (practically not used in computer keyboards since the mid-1990s) (successful use of all the advantages of the reed switch).
- Industrial instrument keyboards where durability and explosion protection are required.
- Sensors: security, bike computers, etc.
- Underwater equipment: lights for diving, spearfishing.
- Elevators: cabin positioning sensors
- TV and radio equipment
The main trend is the replacement of reed switches with solid-state Hall sensors
reed switch
Reed switch(short for " ger metric [magnetized] con tact") - an electromechanical device, which is a pair of ferromagnetic contacts sealed in a sealed glass flask. When a permanent magnet is brought to the reed switch or the electromagnet is turned on, the contacts close. Reed switches are used as proximity switches, proximity sensors, etc.
A reed switch with an electromagnetic coil constitutes a reed relay.
There are also reed switches that open the circuit when a magnetic field occurs, and reed switches with a switching group of contacts.
Reed switches also differ in design features. They are dry (with dry contacts) and mercury, in which a drop of mercury wets the contact surfaces, reducing their electrical resistance and preventing vibration of the plates during operation.
Options:
§ Actuation magnetomotive force- the value of the magnetic field strength at which the reed switch contacts close.
§ Release magnetomotive force - the value of the magnetic field strength at which the reed switch contacts open.
§ Insulation resistance- electrical resistance of the gap between the cores (in the open state).
§ Contact junction resistance- resistance of the contact area, which is formed when the cores are closed.
§ Breakdown voltage- the voltage at which the reed switch breaks down.
§ Response time- the time between the moment of application of the control magnetic field, and the moment of the first physical closing of the electrical circuit by the reed switch.
§ Release time- the time between the moment of removal of the magnetic field applied to the reed switch, and the moment of the last physical opening of the electrical circuit by the reed switch.
§ Capacity- electric capacitance between the terminals of the reed switch in the open state.
§ Maximum number of operations- the number of operations at which all the main parameters of the reed switch remain within acceptable limits.
§ Max Power- the maximum power switched by the reed switch.
§ Switched voltage
§ Switching current
Advantages:
§ The contacts of the reed switch are in a vacuum or in an inert gas and burn slightly, even if a spark occurs between the contacts when closing or opening.
§ Durability of reed switches. It is believed that if you do not beat the reed switch and do not pass very large currents, then the service life of the reed switch is infinite (although the technical data for reed switches indicate restrictions, 10 8 -10 9 and more operations).
§ Smaller size compared to a classic relay rated for the same current.
§ No need to use refractory and precious metals for contacts.
§ Reed switches are almost silent.
§ High (relative to classical relays) performance.
Flaws:
§ The presence of a bounce when turned on, which entails multiple trips in a short period of time.
§ High cost and greater weight compared to open contacts.
§ The need to create a magnetic field.
§ Complexity of installation.
§ Fragility - reed switches cannot be used in conditions of strong vibrations and shock loads.
§ Limited actuation speed
§ Sometimes the contacts "stick" (remain in a closed state) - such a reed switch must be replaced.
Application:
§ Keyboards - keyboard synthesizers and computers (practically not used in computer keyboards since the mid-1990s) (successful use of all the advantages of the reed switch).
§ Industrial instrument keyboards where durability and explosion protection are required.
§ Sensors: security (door opening sensor), bicycle computers, etc.
§ Underwater equipment: lights for diving, spearfishing.
§ Elevators: cab positioning sensors
§ Television and radio equipment
§ Electronic current meters 1-phase and 3-phase (used in apartment buildings,in industry)
magnetic amplifier is a static apparatus designed to control the magnitude alternating current with weak direct current. It is used in circuits for automatic control of AC motors.
Operating principle:
The operation of the magnetic amplifier is based on the non-linearity of the magnetization characteristic of the magnetic circuit. On the extreme rods of the magnetic amplifier there is a working winding, which consists of two coils connected in series. The control winding of a large number of turns W= is placed on the middle rod. If the current is not supplied to it, but to the working winding connected in series with the load, AC voltage U~, then due to the small number of turns W~, the magnetic circuit is not saturated, and almost all the voltage drops on the reactance of the working windings Z~. In this case, little power is released on the load.
If we now pass the current Iу through the control winding, then even with its small value (due to the large W \u003d), saturation of the magnetic circuit occurs. As a result, the reactance of the working winding decreases sharply, and the amount of current in the circuit increases. Thus, by means of small signals in the control winding, it is possible to control a significant amount of power in the working circuit of the magnetic amplifier.
In the simplest case, a magnetic amplifier is a DC-controlled inductance that is connected to an AC circuit in series with the load. With a large inductance, the current in the series circuit and in the load is small, with a small inductance, the current in the series circuit and in the load is large. Exists whole line developments in which a magnetic amplifier is used for doubling the frequency, contactless switching of currents (contactless relays), for stabilizing the supply voltage, for modulating HF signals with LF signals.
Application:
The main purpose is to control a power electric drive (common in construction equipment), they were also used in household AC stabilizers, in lighting controls for cinema and concert halls, in binary computer LEM-1 L. I. Gutenmakher and in ternary computers"Setun" and "Setun-70" N. P. Brusentsov as well as in the control circuits of a diesel locomotive.
Magnetic amplifiers are still used in systems that measure direct currents from strain gauges. Hybrid circuits, combining a miniature magnetic amplifier with a semiconductor one, easily solve the problem of zero drift and have high accuracy.
Electronic amplifiers:
Electronic amplifier- an amplifier of electrical signals, in the amplifying elements of which the phenomenon of electrical conductivity in gases, vacuum and semiconductors is used. An electronic amplifier can be both an independent device and a block (functional unit) as part of any equipment - a radio receiver, a tape recorder, measuring instrument etc.
Gerkomn (short for “hermetic [magnet-controlled] contact”) is an electromechanical device, which is a pair of ferromagnetic contacts sealed in a sealed glass flask. When a permanent magnet is brought to the reed switch or an electromagnet is turned on, the contacts close. Reed switches are used as position sensors, limit switches, etc.
A reed switch with an electromagnetic coil constitutes a reed relay.
There are varieties of reed switches according to the contact group: with a closing contact, an opening contact and a switching contact.
Reed switch with closing contact - the contact is open in the absence of a magnetic field, and closes in the presence of a magnetic field.
Reed switch with opening contact - the contact is closed in the absence of a magnetic field, and opens in the presence of a magnetic field.
A reed switch with a changeover contact has three outputs - in the absence of a magnetic field, one pair of outputs is closed, and in the presence of a magnetic field, another pair of outputs is closed.
Reed switches also differ in design features. They are dry (with dry contacts) and mercury, in which a drop of mercury wets the contact surfaces, reducing their electrical resistance and preventing vibration of the plates during operation.
The difference between a reed switch and a Hall sensor:
Reed switch is an element that mechanically closes (or opens) electrical circuit with a proper change in the magnetic field strength;
Hall sensor is a semiconductor device through which an electric current flows during operation and a transverse potential difference arises, proportional to the magnetic field strength.
The contacts of the reed switch are in a vacuum or in an inert gas and burn slightly, even if a spark occurs between the contacts when closing or opening.
Durability of reed switches. It is believed that if you do not beat the reed switch and do not pass very large currents, then the service life of the reed switch is infinite (although the technical data for reed switches indicate restrictions, 10 3 -10 8 and more operations).
Smaller size compared to a classic relay rated for the same current.
No need to use refractory and precious metals for contacts.
Reed switches are almost silent.
High (relative to classical relays) performance.
Flaws
· The presence of a bounce when turned on, which entails multiple trips in a short period of time.
· Greater weight compared to open contacts.
The need to create a magnetic field.
Susceptibility to external magnetic fields, the need for protection against them
Difficulty of installation.
· Fragility -- reed switches cannot be used in conditions of strong vibrations and shock loads.
· Limited response speed.
Possibility of spontaneous opening of the reed switch contacts at high currents
· Sometimes the contacts "stick" (remain in a closed state) - such a reed switch must be replaced.
Application.
· Keyboards - keyboard synthesizers and computers (practically not used in computer keyboards since the mid-1990s) (successful use of all the advantages of the reed switch).
· Keyboards of industrial devices where durability and explosion safety is required.
Sensors: security (door opening sensor), bicycle computers, top cover laptop (opening and closing), etc.
· Underwater equipment: lights for diving, spearfishing.
Elevators: cab positioning sensors
TV and radio equipment
Single-phase and three-phase electronic current meters (used in apartment buildings, in industry) [source not specified 508 days]
· The main trend is to replace reed switches with solid-state Hall sensors.
· A special area of application is devices for transmitting discrete control signals and protecting against current overloads of high-voltage electrical and radio engineering installations, such as powerful lasers, radars, radio transmitting devices, electrophysical installations, and other types of equipment operating under voltage 10 - 100 kV. Especially for these types of equipment, V. I. Gurevich developed reed relays with high-voltage insulation, the so-called "reed relays" or "high-voltage insulating interfaces", described in his books
Reed switch(short for sealed contact) - an electromechanical device, which is a pair of ferromagnetic contacts sealed in a sealed glass flask. When you bring a permanent magnet to the reed switch or turn on the electromagnet, the contacts close or open, depending on the reed switch you have chosen. Reed switches are used as proximity switches, proximity sensors, etc.
Benefits of using reed switches:
- Due to the fact that the closing and opening conductors are located in a vacuum, they do not oxidize. When closing and opening, a spark does not jump between the conductors. These two features provide tremendous durability to reed switches. It is believed that if you do not beat the reed switch and do not pass very large currents, then the service life of the reed switch is infinite.
- There is no "noise" when switching on and off, there is no "pressing uncertainty". The reed switch can have only two clear states - on and off.
- High current. There is no need for click relays to make or break circuits that carry a lot of current.
They were used in Soviet-made keyboards (from there you can pick up a huge number of them).
Nowadays, they are used in intercoms to detect a lifted tube.
They can be used as relays, keys, sensors, etc., in general, as a fantasy is enough).
But be careful, fragile item.