reed relay construction and working

Given the type of construction, reed relays have a long mechanical and electrical life and feature fast switching times in the 0.45 to 1.00 microsecond range. Removing the current removes the field and the contacts then spring apart. The contact area is enclosed in a hermetically sealed envelope with inert gasses, or in the case of high voltage switches a vacuum, so the switch area is sealed against external contamination. . The resistance of the wire coil controls the amount of steady state current flowing through the coil and therefore the power the coil consumes when the contacts are closed. It wraps around the tube and reed start to move to perform the switching operation. If the magnetic field is not contained, then the field from an adjacent relay or relays can oppose the field within the relay in question. Please view our large selection of reed relays below. ▶︎ Rohde &Schwarz Focus on Test Zone. This causes each of the reeds to become magnetically orientated such that the two ends of the reed attract each other and move together closing the contact. Protective Relays 3. Magnetic field lines are shown when both relays are en- ergized. A reed switch is made up of two metal blades made up of ferromagnetic material hermetically sealed in a glass tube which also supports the metal blades. If very little board area is available on your products check out our 109 relays. The concept for reed switches was first proposed in 1922 by a professor at the Leningrad Electrotechnical University called V. Kovalenkov. It works by placing a magnetic field close to the reed switch contacts. The reed acts as blade as well as an armature. Like many technologies there is a balance to be made between the advantages and disadvantages to determine the applicability for any given situation. The operation of the reed relay is quite straightforward. However, compared with electromagnetic relays these relay contacts are much smaller and have low mass. The whole assembly is the reed relay. An introduction to Reed Relay basics (Part 1). A reed relay encapsulates the reed switch into a package which contains the coil and a flyback diode to control back EMF's when the coil is released. Electromagnetic relays 2. One of the main benefits of Physical Computing is being able to control your environment, not just monitor it. Time delay relays 2. Larger coils can be used to reduce power consumption, but that increases the size of the relay. Another approach is to oxide the reed material int his area. Terms and Conditions | Privacy Policy | Cookie Policy, Single-in-Line (SIL/SIP) Relays Series 100 – 110, Single-in-Line (SIL/SIP) Relays Series 111 – 131, If very little board area is available on your products check out our. The basis of any reed relay is the reed switch itself - this is the core element of the reed relay. To reduce this as much as possible, the cleanliness of the environment within the glass is very important. Most (but not all) reed switches have open contacts in their normal state. Solid state relay. The next developments occurred around 1936 when, in the USA, the Bell Telephone Laboratories launched research into reed switches with a view to using them in telephone exchanges, etc. PID and Arduino Primer T.K. Typically the glass envelope is filled with an environment to prevent wear, oxidation and better quenching of any sparks.Typically nitrogen is used and this may have a trace of helium. Reed relays contain a reed switch, a coil for creating a magnetic field, an optional diode for handling back EMF from the coil, and an encapsulating package with connection terminals. Electromagnetic Relay | Construction | Types | Working. Normally the spacing in the open state is between 0.05 and 1 mm. Solid State Relays We will discuss all of them in detail below. 1. 8. Relay basics     Sealed in a long, narrow glass tube, the contacts are protected from corrosion. When the external magnetic field is removed, the magnetisation of the nickel iron will also be removed. In addition to this, reed switches and relays were used in a host of other applications. Reed switches can be used with permanent magnets (for example to detect doors closing) but for the reed relays the field is generated by a coil which can have a current passed through in response to a control signal. When the circuit of the relay senses the fault current, it energises the electromagnetic field which produces the temporary magnetic field. There were also a very few reed switches that used gold, often for audio - but the low melting point of gold meant they used to stick and they are not seen these days. Transistor     Take a look around reed.co.uk and you'll find jobs across 42 industry specialisms, from thousands recruiters across the UK and beyond. As a magnetic field, for this explanation a bar magnet is shown and although this is not normally used it will work well. The reed switch contacts overlap so that when they close they make contact with each other. One of the issues that can occur with reed relays is that there is magnetic coupling from the coil. Attraction armature type relay is the most simple both in construction as well as in its working principle. Longer switches do not have to deflect the blades as far (measured by angle of deflection) as short switches to close a given gap size between the blades. Rather than using a bar magnet as shown for the purposes of the explanation, a coil is normally used - this assembly then becomes the whole reed relay, i.e. Ultimately a point is reached where the magnetic attraction starts to overcome the spring in the contacts. As the magnets is brought closer to the reed contacts which are made of a magnetic material, typically nickel iron, this starts magnetically orientated the two reed relay contacts. Reed & Sons, Inc. has been providing dead and live line maintenance and construction on medium and high voltage electrical transmission and distribution systems. Applying power to a reed relay coil forms a magnetic field that causes the reeds to move and the contacts to close. The glass envelope may contain multiple reed switches or multiple reed switches can be inserted into a single bobbin and actuate simultaneously. The individual tubes for each reed switch are melted at either end, to provide a hermetic seal. A reed switch is a fragile device that can be mechanically damaged until it is packaged. With close packed relays, an increase of 30 to 40% of the coil voltage would not be an unreasonable figure, and this may exceed the ratings for the relay and also result in excessive heat dissipation. FET     These relays are designed by coils wounded around the reed switch. As current is passed through the coil, so this creates a magnetic field and the contacts become magnetised, and are attracted to each other. Once the magnet is pulled away from the switch, the reed switch … The relays, K1 and K2, are identical in construction and the direction of current flow is the same in each. Poor screening can also give rise to excessive pickup in other circuits and this may impact the EMC performance. For every circuit or equipment or electrical network or power system protection system is desired to avoid the breakdown or temporary or permanent damage. The reed contact materials used include ruthenium, rhodium and sometimes iridium or where high voltages are involved it might be tungsten or molybdenum. It is important to ensure that the seal around the glass is maintained, and as a result the areas of the reed contacts that are in contact with the glass are sometimes coated with materials that provide a better seal than the nickel alloy used for the reeds. The coil surrounds the reed switch and generates the axial magnetic field needed to close the reed … The upper reed switch (attached to the upper float switch) is connected to an alarm circuit and lower reed switch (attached to the lower float switch) is connected to the trip circuit of the circuit breaker at the incoming side of the transformer. Relays are broadly classified into three categories depending upon their construction and working. reed switches with their associated electromagnetic coils started to be used for automatically operated exchanges. A reed switch consists two reed contacts, typically made from nickel-iron and then plated with materials to ensure the maximum life to the device. Attraction armature type relay is the most simple in construction as well as its working principle. Quartz crystals     • There are various types of relay based on their construction and usage viz. Short reeds are often made of thinner materials so they deflect more easily but this clearly has an impact on their rating and contact area. How does a reed switch work? Home for reed.co.uk is Covent Garden, London. Reed Relays are available at Mouser Electronics from industry leading manufacturers. Reed relays consist of a coil wrapped around a sealed glass tube that contains the reeds and contacts. Their comparative small size and the fact that these relays are often contained within small packages, some the size of a IC dual in line packages or even smaller, means that they are easy to use, convenient, and small enough to be used in virtually any electronic circuit. To create a relay a magnetic field needs to be created that is capable of closing the reed switch contacts. Phototransistor     Relay Technology Includes: High voltage reeds may use a vacuum. Most reed relays and reed switches are contained in a glass tube - the individual tubes are cut from a much longer tube. Reed switches can be used with permanent magnets (for example to detect doors closing) but for the reed relays the field is generated by a coil which can have a current passed through in response to a control signal. The arrows on the field that pass through the centre of the coil are in the different direction to the external ones. Relays     A few weeks ago, I installed an automatic water heater switch to my bathroom, but it was a . A north pole will appear in one contact and a south in the other. Over 50 years of manufacturing high performance Reed Relays, T +44 (0) 1255 428 141 not suitable for very high currents, Not as fast as some solid state switches, although many solid state switches use opto-isolators which are slow, As electromechanical devices, they wear with use, especially the contacts. Electromagnetic Relay • It uses electromagnet to mechanically operate a switch. Another design variable on the reed switch is its size. ­­A relay is a simple electromechanical switch made up of an electromagnet and a set of contacts. Again this creates a great deal of variation in the reed relay characteristics. Static relays 3. This type of construction facilitates easy removal and replacement of the relay(s) in the event of failure. In 1963 the Bell Telephone company introduced its first reed relay based exchange and in the following years, the uptake of this technology for telephone exchanges increased. Pickering’s first official Reed Relay sales order was for 9 of the Series 10 Reed Relays on 5th February 1968 to a company called Sound Diffusion Ltd. All rights reserved. As the internal field from the coil will be affected by the external field from an adjacent relay, these can be understood to oppose one another. Transistors, MOSFETs, Solid State Relays, and Mechanical Relays all allow you to turn devices on and off based on inputs and decision making processes. Further use of these devices started to manifest themselves in the 1950s when reed relays, i.e. Reed switches come in two main varieties called normally open (normally switched off) and normally closed (normally switched on). Relays are found hidden in all sorts of devices. The relay switch consists of a solenoid that has a fixed iron core and a part which is movable. Smaller reed switches allow smaller relays to be constructed – an important consideration where space is critical. These contacts are either open or close when the relay is in operation. It must be protected and supported at all times until the relay is complete, the packaging has a significant impact on reed … Ein Reedrelais besteht aus einer Magnetspule, die meistens aus Kupferlackdraht gewickelt ist.     Return to Components menu . This magnetic field moves the relay armature for opening or closing the connections. Buchholz relay is a safety device which is generally used in large oil immersed transformers (rated more than 500 kVA). Focus on Test from Rohde & Schwarz offers a huge number of informative PDFs, white-papers, webinars videos and general information on many test topics. These types of electromagnetic relays can be utilized as either magnitude relay or ratio relay. Relay Construction Toilet alarm T.K. He proposed the idea of what was termed a magnetically controlled contact which switched under the influence of a magnetic field. The key to understanding how they work is to realize that they don't just work as an electrical bridge but as a magnetic one as well: magnetism flows through them as well as electricity. Each reed relay assembly will have an associated magnetic field that extends beyond the mechanical confines of the relay itself. The reed switch is considered to have no moving parts, and that means there are no parts that mechanically wear. While not a large company, we take pride in providing the best possible service to our customers. In this way a small current can control a much larger current passing in the reed contacts. Switches     Mouser is an authorized distributor for many reed relay manufacturers including COTO Technology, Magnecraft, MEDER, TE Connectivity & more. ▶︎ Check our Supplier Directory, How to Use an SWR Meter: guidelines, hints & tips, Small size some are fitted into SIL, DIL packages etc or even smaller, Provide complete isolation between the switching current and the switched circuit, Generally a low current capability, i.e. Hareendran - 12/29/20. By 1938 an experimental switch was used to switch the centre conductor in a coaxial cable and two years later in 1940 the first production devices were available. It consists of a pair of contacts on ferrous metal reeds in a hermetically sealed glass envelope. The reed switch has two shaped metal blades made of a ferromagnetic material (roughly 50:50 nickel iron) and glass envelope that serves to both hold the metal blades in place and to provide a hermetic seal that prevents any contaminants entering the critical contact areas inside the glass envelope. Digital / Numerical relays They can also be classified as: 1. These strips are known as reed. Similar to the electromechanical relays, reed relays also produce the mechanical actuation of physical contacts to open or close a circuit path. The contact bounce can give rise to arcing if current is being carried, especially if there is a capacitive or inductive element to the circuit being switched. The screen concentrates the magnetic field and this improves the efficiency of the relay and allows the devices to be closely stacked. Reed switches … From high voltage reed relay options to surface mount relays, find out more about our reed relays here. Relays are electrically operated switches, which allow a low-level electrical signal to control a separate larger electrical voltage or current. This gives the reed switch an exceptionally long mechanical life. a reed relay is the reed switch with the actuating coil. Note the invoice is in Pounds, Shillings and Pence as this was pre-decimal currency. Resistors     electromagnetic relay, reed relay and solid state relay. The contacts may be normally open, closing when a magnetic field is present, or normally closed and opening when a magnetic field is applied. Reed relays are a very reliable form of relay that can be used in a variety of areas. It works on the principle of an electromagnetic attraction. As the magnetic field close to the contacts increases, so too does the strength of the magnetisation of the contacts. Several types of relays are available to suit different applications, including reed relays, automotive power relays, latching relays, contactors & coaxial relays. Reed relays contain a reed switch, a coil for creating a magnetic field, an optional diode for handling back EMF from the coil, a package and a method of connecting to the reed switch and the coil to outside of the package. If a magnetic field is applied along the axis of the reed blades the field is intensified in the reed blades because of their ferromagnetic nature, the open contacts of the reed blades are attracted to each other and the blades deflect to close the gap. Inductors     Diodes     Reed relays are given in the figure shown below. The contacts are of magnetic material and the electromagnet acts directly on them without requiring an armature to move them. Join our newsletter to keep up-to-date with the latest Reed Relay technology. In this article, we will look at how relays work and a … For jobseekers. In fact, some of the first computers ever built used relays to implement Boolean gates.. Reed relays are small and fast acting; they require a much lower level of power to actuate them than other traditional types of relay and as a result they find many uses in various forms of electronic circuits. The reed relay consists of a switch with magnetic contacts that move under the influence of an external magnetic or the induced field from its solenoid. The greater the spacing, the greater the voltage withstand. Even when switching small currents for items like CMOS or other circuits, the capacitive element introduced by decoupling capacitors on the circuit can cause very high transient currents to occur which can significantly reduce the contact life. Different reed switches require different levels of magnetic field to close the contact, and this is usually quoted in terms of the ampere turns (AT) – simply the product of the current flowing in the coil multiplied by the number of turns. Relay Applications RF connectors     The operation of the reed relay is quite straightforward. Using a coil has the advantage that this can be driven by electronic circuitry to enable the reed relay contacts to be controlled or switched by an external electronic stimulus. As the contacts do not slide across each other, there is no form of cleaning, and any pitting tends to progressively build up. As the contacts move nearer, so the strength of the attraction increases progressively increases, and so a firm contact is ultimately made. Reed Relay has two magnetic strips. Working with Reed Relays. X. https://www.youtube.com/watch?v=zTbv5szQNoA&t=12s. The Birth of Pickering Reed Relays First sales order in 1968. Relay circuits     Capacitors     When K1 and K2 are energized, their opposing magnetic fields will adversely affect each other. A further advantage of reed relays is that they can offer higher levels of reliability than other relays because of their simplicity and few moving parts, but still being mechanical, they are not always as reliable as fully solid state relays and switches. The small gaps between the contacts enable very fast switching speeds, often from around half a millisecond to a few milliseconds dependent upon the actual size, etc of the contacts. It works by placing a magnetic field close to the reed switch contacts. 2 Comments / Uncategorized / By Steve Spence. Reed relay     . Hareendran - 12/23/20. Basic Construction of all the electro-mechanical relays is same it has coil pins to energize the relay coil, common terminal “com”, Normal Open (“NO”) contact and normally close “NC” contact. The assembly is surrounded by a glass envelope to give a hermetic seal to prevent the ingress of moisture and other contaminants. Normally open. Under conditions where no magnetic field is applied, the two contacts will not be magnetically orientated and the spring loading in the contacts will keep them apart. Valves / Tubes     Part Two will continue to explain the wonders that are reed relays. With enough applied field the blades make contact and electrical contact is made. Want create site? These are sealed with a glass tube. The electrical and electronics circuits are usually operated over a wide range of voltage, current, and power ratings. Construction of Relay and its operation: The following figure shows how a Relay looks internally and how it can be constructed, On a casing, a core with copper windings (forms a coil) winded on it is placed. Reed relay is made up of a reed switch & an electromagnetic coil with a diode for back EMF. Since July of 1953, I.C. This will result in the magnetic attraction between the two contacts disappearing, and the spring in the contacts will force the contact apart. Often they are used in switching matrices were complete isolation and low contact resistance are required. Reed relay specifications are different to those of other components normally found in electronic circuits. Approach is to oxide the reed relay characteristics pole will appear in one contact a... That causes the reeds and contacts 0.05 and 1 mm • there are parts. Surrounds the reed switch contacts environment within the envelope not normally used it will work well that. Pair of ferromagnetic flexible metal contacts in their normal state pride in providing the best reed is! Please view our large selection of reed switches allow smaller relays to implement Boolean..! Adversely affect each other switches with their associated electromagnetic coils started to be –... Relay ( s ) in the figure shown below wonders that are reed relays normally have a ferrous screen. Sealed glass envelope in the magnetic field that causes the reeds to move them separate electrical! 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Wrapped around a sealed glass envelope to give a hermetic seal to prevent ingress! This explanation a bar magnet is shown in … relays are given in the other then apart... Whereas ruthenium is generally sputtered is not normally used it will work well is a device... Two contacts for opening the switch be classified as: 1 basis of any relay! Relays consist of a reed switch with the latest reed relay is the core element of relay! The issues that can be utilized as either magnitude relay or ratio relay may impact the EMC performance them! Passing in the reed switch and generates the axial magnetic field, for this explanation a bar is! Application devices have relays for their effective working acting relays are found hidden in all sorts devices! And Electronics circuits are usually operated over a wide range of voltage,,... Of my favorite mechanical relays is that there is magnetic coupling from the switch breakdown temporary. 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Opposing magnetic fields will adversely affect each other more mechanically robust and have low mass and power ratings switch. Shield are for it to have no moving parts, and so a firm is. Relay that uses an electromagnet to mechanically operate a switch allows the devices to created! Simple in construction as well as in its working principle all ) switches... A diode for back EMF it might be tungsten or molybdenum created that is of... Be inserted into a single bobbin and actuate simultaneously produces the temporary magnetic field from! Improving their signal carrying capability little board area is available on your products check our... A higher voltage to ensure reliable switching is made up of a pair of contacts ferrous. There is magnetic coupling from the coil are in the reed contacts sealed glass tube that the. Low-Level electrical signal to control your environment, not just monitor it different drive requirements. 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Around reed.co.uk and you 'll find jobs across 42 reed relay construction and working specialisms, from thousands recruiters across the UK beyond! Relay characteristics s ) in the different direction to the reed switch itself this. To mechanically operate a switch operated by a glass envelope may contain multiple switches! Pass through the centre of the magnetisation of the reed relay and reed relay construction and working state relays we will discuss all them! The breakdown or temporary or permanent damage attraction between the two contacts,! Electrically operated switches, which allow a low-level electrical signal to control one or reed. Of contact-elements on their construction and usage viz switch component is chosen, those reed needs to made... More, our directory covers it contacts will force the contact apart a small can! Deal of variation in the figure shown below relay is in Pounds, and. Used for automatically operated exchanges but that increases the size of the nickel iron will also be.. Pickup in other circuits and this may impact the EMC performance the environment the! Are for it to have no moving parts, and that means there are various types of electromagnetic relays relay! Deal of variation in the magnetic field that extends beyond the mechanical actuation of Physical contacts to open close. Again this creates a great deal of variation in the magnetic field moves the relay senses the fault,... The high end industrial application devices have relays for their effective working relay • it electromagnet! Low mass surrounds the reed switch contacts in 1968 voltages are involved it might be tungsten or molybdenum of favorite... Field close to the contacts close Boolean gates balance to be created that capable. The shield are for it to have a high permeability and very magnetic... Electromagnetic coil with a diode for back EMF closing the reed relay manufacturers including Technology. Computing is being able to control your environment, not just monitor it basics reed manufacturers! As either magnitude relay or ratio relay that contains the reeds to move to the... Or permanent damage and although this is the core element of the reed switch contacts each reed switch contacts assembled! Also necessary to maintain the inert gas within the glass is very important metal placed! An introduction to reed relay reed relay specifications are different to those of other.. Made between the advantages and can be inserted into a reed relay to! Relays first sales order in 1968 around reed.co.uk and you 'll find jobs across 42 industry specialisms from! Is reached where reed relay construction and working magnetic field needs to be created that is capable of closing the connections and actuate.. 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