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In this article, we will provide you the basic information of relay: what is a relay? What types of relays are there? What are their characteristics? How to maintain the common faults of the relay? With these questions, let us find the answers in the article together.     Catalog     I. What is a Relay?     1.1 Electrical Symbol     1.2 Contact Form     1.3 Functions of Relay II. Relay Classification III. Main Types of Relay IV. How to Test a Relay V. Influencing Factors of Relay Reliability VI. Maintenance of Common Faults of Relay VII. Example Explanation: Delay Relays FAQ   I. What is a Relay? This video will explain what is a relay, and how does a relay works with basic information about construction and different types of relay.   Relay is a kind of electric control device. When the change of input quantity (excitation quantity) reaches the prescribed requirement, the controlled quantity will be changed step by step in the electric output circuit. It has an interactive relationship between the control system (also known as the input loop) and the controlled system (also known as the output loop). Usually used in an automatic control circuit, it is a kind of automatic switch which uses a small current to control the operation of a large current. Therefore, it can play the role of automatic regulation, safety protection, conversion circuit, and so on.   1.1 Electrical Symbol A relay is composed of two parts: coil and contact group, the graphic symbol of the relay in a circuit diagram also includes two parts: a box for coil and a set of contact symbols for contact combination. When the contact circuit is relatively simple, the contact group is often drawn directly on one side of the circle frame, which is called centralized representation.   Relay coils are represented by a rectangular symbol in the circuit, and if the relay has two coils, draw two side-by-side boxes. The contacts of relays are represented in two ways: one is to draw them directly on the side of the box, which is more intuitive. The other is to draw each contact point into its own control circuit according to the need for circuit connection. Usually, the contact of the same relay is marked with the same text symbol, and the contact group is numbered to show the difference.   1.2 Contact Form There are three basic forms of contact for relays: 1. The two contacts are disconnected when power off, and the two contacts are closed when power on.   2. The two contacts are closed when power off and the two contacts are disconnected when the power on.    3. The contact group has three contact points, that is, a moving contact in the middle and a static contact in the upper and lower parts of the contact group, respectively. When the coil is power-off, the dynamic contact is disconnected from one of the static contacts and connected with the other. After the coil is power-on, the dynamic contact moves, the connecting contacts state is opposite to the power-off state to achieve the purpose of conversion. Such contact groups are called switching contacts.      1.3 Functions of Relay Relay is an automatic switching element with an isolation function. It is widely used in remote control, telemetry, communication, automatic control, electromechanical integration, and power electronic equipment. It is one of the most important control components.   The relay generally has induction parts (input section) that can reflect a certain input variable (such as current, voltage, power, impedance, frequency, temperature, pressure, speed, light, etc.); an executing part (output section) capable of realizing power-on and power-off state of the controlled circuit. Between the input port and the output port of the relay, there is also an intermediate mechanism (driving section) for coupling the input, the function processing, and the driving of the output.   As a control element, relays generally have the following functions:   1) Expand the control range: for example, when the control signal of the multi-contact relay reaches a certain value, the multi-circuit can be switched on and off at the same time according to the different connecting forms of the contact group.   2) Amplification: a very small volume can control a large power circuit, such as sensitive relays, intermediate relays, etc.   3) Synthesis signal: when a plurality of control signals input multiple winding relays in the prescribed form, a predetermined control effect can be achieved by comparing and synthesizing.   4) Automatic, remote control, monitoring: relays on the automatic device, together with other electrical appliances, can form a program control circuit to achieve automatic operation.   II. Relay Classification   1. According to the working principle or structural characteristics of relays: 1) Electromagnetic relay: an electrical relay that is driven by the suction of an input circuit between an electromagnet core and an armature. 2) Solid relay: a relay in which electronic components perform their functions without mechanical movement, and the input and output are isolated. 3) Temperature relay: a relay that operates when the external temperature reaches a certain value. 4) Reed relay: a relay operates by a reed that is sealed in a tube and has a dual action caused by the electricity action on the reed and the armature. 5) Time relay: When the input signal is added or removed, the output part needs to be delayed or limited to a specified time to close off. 6) High-frequency relay: a relay used for switching a high frequency, a radio frequency circuit which had a minimum loss. 7) Polarization relay: a relay driven by magnetic field synthesis caused by a polarized magnetic field and a controlled current acting through the magnetic field generated by the control coil. The direction of the operating relay depends on the direction of the current flowing through the control coil. 8) Other types of relay: optical relay, sound relay, thermal relay, instrument relay, Hall effect relay, differential relay, etc.   2. According to shape size of relays: 1)miniature relay  2)subminiature relay 3)small miniature relay Note: for sealed or enclosed relays, the size is the maximum of the three vertical dimensions of the relay body, excluding the dimensions of mounting, leading end, rib pressing, edge pressing, flanging, and sealing solder joint.   3. According to the load of the relays: 1) micro power relay 2) small power relay 3) medium power relay 4) high power relay    4. According to the protective characteristics of relays: 1) sealed relay  2) enclosed relay 3) unenclosed/ open relay   5. According to the principle of action: 1) electromagnetic type 2) induction type 3) rectifier type 4) electronic type 5) dig type   6. According to the physical quantity of the reaction: 1) current relay 2) voltage relay 3) power relay 4) impedance relay  5) frequency relay 6) gas relay   7. According to the role of relays in the protection circuit: 1) starting relay  2) measuring relay  3) time relay 4) auxiliary/intermediate relay 5) signal relay 6) exit relay    III. Main Types of Relay   1) electromagnetic relay As long as a certain voltage is added at both ends of the coil, a certain current will flow through the coil, producing an electromagnetic effect, and the armature will contact the iron core under the action of electromagnetic force attraction, thus driving the armature dynamic contact and static contact (normally open contact) suction. When the coil is powered off, the electromagnetic suction also disappears, and the armature will return to its original position in the reaction force of the spring and release the dynamic contact from the original static contact (normally closed contact). In this way to achieve the purpose of switching on and off. In addition, it can be distinguished the "normal open and closed contacts of the relay.   Note: The static contact in the broken state when the coil is powered off is known as the "normal open-contact"; the static contact in the on-state is called the "normal closed-contact". Relays generally have two circuits, a low-voltage control circuit, and a high-voltage working circuit.   2) solid-state relay  A solid-state relay is a kind of four-terminal device with two connection terminals as input and the other two as output. In the middle, an isolation device is used to realize the electrical isolation of the input and output.   Solid-state relays can be divided into AC type and DC type according to the type of load power supply. According to the switch, type can be divided into normal open type and normally closed type. According to the isolation type, it can be divided into hybrid type, transformer isolation type, and photoelectric isolation type, and the photoelectric isolation type is the most.   3) thermal reed relay A thermal reed relay is a new type of thermosensitive switch which uses thermosensitive magnetic material to detect and control temperature. It consists of a temperature-sensitive magnetic ring, constant magnetic ring, reed tube, heat conduction mounting sheet, a plastic substrate, and other accessories. Thermal reed relays do not use coil excitation but are driven by magnetic forces generated by constant magnetic rings. In addition, whether the constant magnetic ring can provide magnetic force to drive the reed tube is determined by the temperature control characteristic of the temperature sensing magnetic ring.     4) reed relay Reed relay is a kind of coil sensing device, which uses a coil to produce a magnetic field to drive a magnetic reed tube. In addition, the characteristics of reed relays include small size, lightweight, fast reaction speed, short jump time, and so on.   When a whole piece of ferromagnetic metal or other conductive material is close to it, turn on or turn off the circuit. Reed relay consists of a permanent magnet and a reed tube. Both of them fixed to a bracket without magnetism or magnetic conduction. Take the line of the permanent magnet's north-south pole as the axis, which should be coincident or basically coincident with the axis of the reed. From far to near, adjust the distance between the permanent magnet and the reed tube, and fix the position of the magnet when it happens to move (turning off for normally open reed tube and turning on for normally closed reed tube). At this point, when there's a whole piece of magnetic material, and when the iron plate is close to the magnet and the reed tube at the same time, the reed tube will move again and return to the state without magnetic field action; when the iron plate leaves, the spring tube will move in the opposite direction. The reed relay has a strong structure, sealed contact, and high durability. It can be used as a position limiting switch for mechanical equipment, and can also be used to detect whether iron doors, windows, etc.    5) optical relay An optical relay is a semiconductor relay used in AC/ DC, refers to the integration of light-emitting and light-receiving devices. The input side and the output side are electrically insulated, but the signal can be transmitted through the optical. Its characteristics are semi-permanent, micro-current, high impedance, insulating, voltage-resistance, ultra-small, optical-transmission, contact-free, and so on.   It is mainly used in measuring equipment, communication equipment, security equipment, medical equipment, and so on. 6) time relay Time relay is a kind of control apparatus that uses electromagnetic principle or mechanical principle to realize time delay control. There are many kinds of it, such as air damping type, power-driven type, and electronic type.   Air damping time relay is often used in AC circuit, which uses the principle of air throttling through orifice compensation to obtain delay action. It consists of an electromagnetic system, delay mechanism, and contact. Time relay can be divided into two types: power-on delay type and power-off delay type.   The time delay range of the air-damping time relay is large (0.4~60s and 0.4~180s). Its structure is simple, and its accuracy is low. When the coil is electrified (voltage specification is ac380v, ac220v or dc220v, dc24v, etc.), the armature and bracket are attracted by the iron core and moved down instantly, so that the instantaneous action contact is turned on or off, and meanwhile, the piston rod and lever cannot fall with the armature at the same time, because the upper end of the rod is attached to the rubber film in the air chamber, and when the rod begins to move downward under the action of the released spring, the rubber film falls downward. Air becomes thin in the upper air chamber and the damping piston rod drops slowly. After a certain period of time, the piston rod drops to a certain position, then pushes the delay contact action through the lever, causing the dynamic break contact to break and the dynamic close contact turned off. From the coil to the delay contact to complete the action, this time is the delay time of the relay. The delay time can be changed by adjusting the size of the air chamber inlet hole. After the suction coil is powered off, the relay is restored by the action of the recovery spring, and the air was ejected quickly through the vent hole. 7) auxiliary relay a. characteristics of auxiliary relay:   The relay is composed of several high-quality sealed small relays with low coil voltage, which is damp-proof, dust-proof, non-breaking, high reliability, and overcomes the shortcomings of the electromagnetic auxiliary relay wire which is too thin and easy to break. Low power consumption, low-temperature rise, no need to attach high-power resistance, easy installation and connection, large capacity of a relay contact, long working life, easy to observe on the spot, and so on. The delay only needs to be adjusted by the dial switch on the panel, the delay precision is high, and the delay range can be set freely in 0.02S~ 5.00S.   Purpose of intermediate relay: auxiliary relay is used in various protection and automatic control lines to increase the number of contacts and the capacity of contacts in the protection and control loop.   b. classification of auxiliary relays:   static auxiliary relay   delay auxiliary relay   electromagnetic auxiliary relay   elevator auxiliary relay   rail auxiliary relay   c. auxiliary relay principle   When the coil is electrified, the moving iron core is absorbed under the action of the electromagnetic force, and the moving contact action is driven so that the normally closed contact is separated and the normally open contact is closed. When the coil is powered off and the moving iron core drives the dynamic contact to reset under the action of the spring. The working principle of the relay is that when a certain input (such as voltage, current, temperature, velocity, pressure, etc.) reaches a predetermined value, it operates. In order to change the working state of the control circuit, so as to achieve the established purpose of control or protection. In this process, the relay mainly plays a role in the transmission of the signal.   d. function of the auxiliary relay   The general circuit is often divided into two parts of the main circuit and a control circuit. The relay is mainly used for a control circuit, and the contactor is mainly used for the main circuit. Through the relay, using one control signal can control the other one or several signals, and the control of starting, stopping, linkage, and so on. The main control object is a contactor, the contact of the contactor is relatively large, and the carrying capacity is strong, but the control of weak current too strong electricity can be realized through the contactor, and a control object is an electric appliance.   1. Replace small contactor   The contact of the auxiliary relay has a certain load capacity. When the load capacity is small, it can be used instead of the small contractor, such as the electric shutter and the control of some small appliances. This advantage is that not only can play the purpose of control, but also can save space so that the electrical control part of the more refined.   2. Increase the number of contacts   This is the most common use of auxiliary relays, for example, in a circuit control system where a contact needs to control multiple contactors or other components, adding an auxiliary relay to the line.   3. Increase contact capacity   We know that although the contact capacity of the auxiliary relay is not very large, it also has a certain capacity with load, and the current required for its drive is very small. Therefore, the auxiliary relay can be used to expand the contact capacity. For example, it is not possible to use induction switches directly and the output of the transistor to control the heavy load of electrical components. In fact, the auxiliary relay is used in the control line, and the other load is controlled by the auxiliary relay to enlarge the control capacity.   4. Convert pin type   In the industrial control circuit, it is often necessary to use the normally closed contact of the contactor to achieve the control purpose. However, the normally closed contacts carried by the contractor are not enough to achieve the control task. At this time, an auxiliary relay can be parallel to the original contactor coil, and the corresponding components can be controlled by the normally closed contact of the auxiliary relay, and the contact type can be transformed to achieve the desired control purpose.   5. As a switch In some control circuits, intermediate relays are often used to turn on and off some electrical components, such as automatic demagnetization circuits common in color televisions or displays, and transistor controls the on and off of intermediate relays, which are controlled by the opening and closing of their contacts, such as color televisions or displays. So as to control the demagnetization coil on-off action.   6. Switching voltage   7. Eliminating interference in the circuit   8. Power direction relay   An electrical appliance that causes the controlled output circuit to be switched on or off when the input (such as voltage, current, temperature, etc.) reaches a specified value. It can be divided into two categories of electrical volume (such as current, voltage, frequency, power, etc.) relay and non-electrical volume (such as temperature, pressure, speed, etc.) relay. It has the advantages of fast movement, stable work, long service life, small volume, and so on. Widely used in power protection, automation, motion, remote control, measurement, and communication devices.       Common Types   1. overcurrent relay The overcurrent relay is a relay that operates from the current beyond its set value and can be used as a system line and overload protection. The most commonly used is an induction type overcurrent relay, which is opposite to the rotating disk of aluminum or copper by an electromagnet. The rotating disc is rotated by means of the electromagnetic induction principle so as to achieve the protective effect.   action principles:   The inductive overcurrent relay uses the secondary current of the current transformer to generate a magnetic field in the relay to cause the disk to rotate, but the current flowing through the relay must be greater than the current value of a certain current to rotate.   2. overvoltage relay  Overvoltage relay, its main purpose is that when the abnormal voltage of the system rises to more than 120% rating, the overvoltage relay operates so that the circuit breaker can jump off and protect the electric equipment from damage. The construction and operation principle of induction overvoltage relay are similar to those of overcurrent relay, except the main loop.   3. under voltage relay The under voltage relay is constructed in the same way as the overvoltage relay, except that the inner contact and the turntable turn immediately when the voltage is applied.   4. ground overvoltage relay The grounding overvoltage relay has the same structure as the overvoltage relay, and uses a three-phase three-wire non-grounding system, and is connected to the earthing transformer with an open triangle earthing to detect zero-phase voltage.   5. grounding overcurrent relay Grounding overcurrent relay, abbreviated as GCR, is a kind of high-voltage line earthing protection relay.   Main uses:   1) grounding overcurrent protection of high resistance grounding system.   2) grounding protection of generator stator winding.   3) layer short circuit protection of phase-separated generator.   4) overheat protection of grounding transformer.   6. selective grounding relay Selective grounding relay, also called directional grounding relay, is used in non-grounding systems to protect distribution lines. In addition, it can also be used in overhead lines and cable systems.   Selective grounding relay: if a zero-phase sequence current is detected by a grounding voltage transformer when a line is grounded, the selective grounding relay can accurately detect the fault line and alert it and disconnect it according to the requirement. And then continue to send electricity to the normal operating line.   7. free-phase relay In the three-phase line, phase-failure relay or phase-failure protection relay will burn out the single-phase operation of the motor if it does not cut off the line immediately when there is a one-wire break in the power supply end and causes the single-phase.   8. percentage differential relay A percentage differential relay is used as the AC motor of the transformer. Alternator with differential protection and over-current protection relay used as the protection devices, and when abnormal current generated by external fault flows over protection equipment, if current on the transformer is unbalanced or inconsistent with the characteristics of the current transformer, in these cases, this phenomenon will extend several times and cause failure operation to the relay.     IV. How to Test a Relay Relay is the key device in the intelligent prepaid electric energy meter, the life of the relay determines the life of the meter to a certain extent, thus the performance of the relay is very important to the operation of the intelligent prepaid electric energy meter. There are many manufacturers of relays around the world. Their production scale is quite different, the technical level and performance parameters are very different. Therefore, the manufacturers of electric energy meters must have a set of perfect testing devices when detecting and selecting relays. To ensure the quality of the meter. At the same time, the national power grid has also strengthened the sampling detection of the relay performance parameters in the intelligent electric energy meter, which also needs the corresponding testing equipment to check the quality of the meter produced by different manufacturers. However, at present, relay testing equipment is not only a single test item, but detection process also can not be automated completely, the detection data needs manual processing and analysis, the detection results are random, artificial, and the detection efficiency is low, in addition, there is no guarantee of safety.   According to the test requirements of relay performance parameters, the test items can be divided into two categories: one is the test items without load current, such as operating value, contact resistance, service life; the other, test items with load current, such as contact voltage, electrical life, overload capacity.   1.Measuring coil resistance: the multimeter R×10Ω barrier can be used to measure the resistance value of the relay coil, so as to judge whether there is an open circuit phenomenon in the coil. The resistance value of the relay coil is closely related to its working voltage and current. And the service voltage and working current can be calculated by the resistance value of the coil.   2. Contact resistance measurement: using the resistance barrier of the multimeter, the resistance value of the normally closed contact and the moving point resistance should be 0, and the resistance value of the normally open contact and the moving point shall be infinitely large. From this, you can distinguish between the normally closed contact and the normally open contact.   3. Measure the pull-in voltage and current: using an adjustable voltage stabilizing power supply and ammeter, input a set of voltages to the relay, and connect the ammeter in the power supply circuit to monitor. Slowly raise the power supply voltage and note down the pull-in voltage and current when the relay absorbs sound. To be accurate, you can try a few more times and get the average value. Measurement of release voltage and discharge current: it is also like the above-mentioned connection test, when the relay suction, then gradually reduce the power supply voltage, when heard the relay again release sound, note the voltage and current at this time, in addition, you can also try more than a few times to get an average release voltage and current. Generally, the release voltage of the relay is about 10% of the pull-in voltage, and it will not work properly if the release voltage is too small (less than 1/ 10 of the pull-in voltage), which will affect the stability of the circuit and the device operation.   1. Understand the necessary conditions firstly.   1) The power supply voltage of the control circuit can provide the maximum current.  2) Voltage and current in the controlled circuit. 3) The requiring contacts on the controlled circuit. When the relay is selected, the power supply voltage of the general control circuit can be used as the basic factor for selection. The control circuit should provide sufficient working currently for the relay, otherwise, the relay absorption is unstable.   2. After consulting the relevant information to determine the applying conditions, you can find out the type and specification number of the relays required. If you already have a relay on hand, you can check whether it can be used against the data. Finally, consider whether the size is appropriate.   3. Pay attention to the volume of the apparatus. For general electrical appliances, consider the volume of the chassis and the layout of the circuit board installation. For small electrical appliances, such as toys, remote control devices should select ultra-small relay products.     The main test items are briefly described as follows:    (1) Operating value: The voltage required for relay action.    (2) Contact resistance: When electric contact closes, the resistance value between two contacts.   (3) Mechanical life: In the case of the mechanical part without damage, the relay switching times.   (4) Contact voltage: When the electric shock is closed, a certain load current is applied in the electric shock circuit, at this time, the voltage value between the contacts.    (5) Electric life: When the rated voltage is applied on both ends of the relay drive coil and the rated resistive load is applied in the contact circuit, the reliable operation times of the relay under the condition of duty cycle 1:4 less than 300 cycles per hour.    (6) Overload capacity: When the rated voltage is applied on both ends of the relay drive coil and 1.5 times rated load is applied in the contact circuit, the reliable operation times of the relay under the condition of (10 ±1) times/ minute (operation frequency). V. Influencing Factors of Relay Reliability   1.The influence of environment on relay reliability: the average fault interval time of relay working in GB and SF is the highest, reaching 820000h, while in the NU environment, it is only 60000h.   2.The effect of quality grade on relay reliability: the average failure interval of the A1 relay is 3660000h, while that of the C class relay is 110000, the difference between them is 33 times. It can be seen that the quality level of the relay has a great impact on its reliable performance.   3.The effect of the contact form on the reliability of relay: the contact form of the relay will also affect its reliability. The reliability of the single-throw relay is higher than that of the double-throw relay with the same number of tools, and the reliability decreases gradually with the increase of tool number, in addition, the reliability of a single-throw relay is higher than that of the double-throw relay with the same number of cutters. The average failure interval of a single-pole, single-throw relay is 5.5 times that of a four-pole double-throw relay.   4.The influence of structures on relay reliability: there are 24 types of relay structures, and all of them have an influence on the reliability of the relay.   5.Effect of temperature on the reliability of relay: the operating temperature range of the relay is between -25℃ and 70℃. With the increase of temperature, the average time between failures of the relay gradually decreases.   6.The effect of operating rate on relay reliability: with the increase of relay operating rate, the average fault interval time decreases exponentially. Therefore, if the designed circuit requires the relay to operate at a very high speed, it is necessary to carefully detect the relay in order to replace it in time for circuit maintenance.   7.The effect of the current ratio on the reliability of the relay: the so-called current ratio is the ratio of the operating load current of the relay to the rated load current. The current ratio has a great influence on the reliability of the relay, especially when the current ratio is greater than 0.1, the average fault interval time is rapidly reduced, and the current ratio is less than 0.1, the average fault interval time is basically unchanged, therefore, the load with a larger current rating is selected to reduce the current ratio when the circuit is designed because this ensures that the relay and even the entire circuit are not reduced in reliability due to the fluctuation of the operating current. VI. Maintenance of Common Faults of Relay   a. Maintenance of the sensing mechanism For electromagnetic (voltage, current, intermediate) relay, its sensing mechanism is the electromagnetic system. The fault of the electromagnetic system is mainly focused on the coil and the moving and static iron core.   1) coil fault Coil faults are usually caused by coil insulation damage; mechanical injuries form a turn-to-turn short circuit or grounding. Because the power supply voltage is too low, and dynamic, static core contact does not connect tightly, resulting in the current through the coil is too large, the coil heated to burn. The coil should be rewound during the repair. If the armature is not sucked after the coil is electrified, it may be that the wire connection of the coil is removed, so that the coil is short-circuited, therefore, the joint should be re-welded.   2) iron core fault The main fault of the iron core is that the armature can not be absorbed after the power on, which may be caused by the broken coil, having impurities between the moving and static iron core, and the low voltage of the power supply, thus repair should be differentiated. After the power on, the armature noise is big, this may be due to moving or static core contact surface is not smooth, or there is oil on the surface. During repair, the coil should be removed, filing or flattening the contact surface, and oil should be cleaned. Noise may be due to short-circuit or ring fracture, replacing new short-circuit ring to repair. After power loss, if the armature cannot be released immediately, possibly because the moving armature is stuck, the air gap of the iron core is too small, and the spring strain and the contact surface of the iron core have been polluted by oil. Taking maintenance should be differentiated according to the cause of the fault, or adjust the size of the air gap, or replace the springs, or use gasoline cleaning oil.   For the thermal relay, the sensing mechanism is the thermal component, and the common fault is that the thermal component burns out, or operation failures of the thermal element and does not operate.   (1) Thermal component burnout. This may be due to a short circuit on the load side or the high frequency of action of the thermal element. The thermal components should be replaced during maintenance and the setting value should be adjusted again. (2) Operation failure of thermal component. This may be due to the setting value is too small, the operation without overload, or the strong impact and vibration influence, make its action mechanism loosening and tripping. (3) No operation of thermal component. This may be due to the setting value is too small to lose the thermal element overload protection function. During maintenance, the setting current should be adjusted according to the overload working current.   b. Inspection and repair of executing parts Most relay actuators are contact systems. Through its "power on" and "power off" to complete a certain control function. Contact system faults generally caused by contact overheating, wear, melting soldering, and so on. The main reasons for contact overheating are insufficient capacity, insufficient contact pressure, surface oxidation or uncleanliness, etc. The main cause of wear is that the contact capacity is too small, the arc temperature is too high to cause contact metal oxidation, and so on. The main cause of contact melting soldering is that the arc temperature is too high, or the contact is seriously moved, and so on.   The order of maintenance of the contacts is as follows:   1) Open the outer cover and check the contact surface. 2) If the contact surface is oxidized, it is not necessary for the silver contact to be processed, and the oxide layer on the surface of the Cu contact may be lightly scraped with a file or a knife with a knife. 3) If the contact surface is not clean, clean it with gasoline or carbon tetrachloride. 4) If there is a burning trace on the surface of the contact, it is not necessary to repair the silver contact, and the copper contact should be repaired by a file or with a knife. Sand cloth or sandpaper is not allowed to be used for refurbishment, to avoid poor contact due to the residual stand. 5) Contact should be replaced if it welded. If the contact capacity is too small, replace the relay with a larger capacity. 6) If the contact pressure is insufficient, adjust the spring or replace the spring to increase the pressure, if the pressure is insufficient, the contact should be replaced.   c. Maintenance of intermediate part   1) In that air-type time relay, the intermediate part is mainly an airbag. The common faults are time delays. This may be because the airbag is not tight or air-leak, the action delay is shortened, and even the delay is not delayed; it is also possible that the air passage of the airbag is blocked so that the action delay is prolonged. In terms of repair, the former shall reassemble or replace the new airbag, and the latter should open the air chamber and remove the blockage. 2) For the speed relay, its rubberwood pendulum belongs to the intermediate part. If the motor can not stop braking during reverse braking, it is possible that the tilting rod of rubberwood is broken, and it should be replaced when overhauled.     VII. Example Explanation: Delay Relays RF Cafe has said "Relays are a topic that never goes out of date even with the advent of fully solid state relays that use semiconductors in the conduction path,there are still many applications that only mechanical contacts can satisfy." in April 1967 electornics world. It is true that there are switching diode arrays that can handle very high powers,but they are typically expensive compare with relays. Today, let's talk about something about time-delay relays.     What is time delay relays? Time delay relays are simply control relays with a time delay built in. Their purpose is to control an event based on time. The difference between relays and time delay relays is when the output contacts open & close: on a control relay, it happens when voltage is applied and removed from the coil; on time delay relays, the contacts can open or close before or after some time delay. Time delay relays have an important influence in industrial contor logic circuits. There are some examples following:   Flashing light control (time on, time off): two time-delay relays are used in conjunction with one another to provide a constant-frequency on/off pulsing of contacts for sending intermittent power to a lamp. Motor soft-start delay control: Instead of starting large electric motors by switching full power from a dead stop condition, reduced voltage can be switched for a “softer” start and less inrush current. After a prescribed time delay (provided by a time-delay relay), full power is applied. Furnace safety purge control: Before a combustion-type furnace can be safely lit, the air fan must be run for a specified amount of time to “purge” the furnace chamber of any potentially flammable or explosive vapors. A time-delay relay provides the furnace control logic with this necessary time element.   How does time delay relay work? Time delay relays can provide simple, reliable, and economical control. Adjusting the delay time is often as simple as turning a knob. Providing time-delayed switching to start a motor, control a load, or affect a process, TDRs are typically used in industrial applications and OEM equipment. Additionally, they play an important role for targeted logic needs, such as in a small panel or in sub-panels. They have a variety of features and operating characteristics, such as compactness, economy, simplicity, and ease-of-use.Time delay relays not only can be available as plug-in devices but aslo as single-function,single-time-range devices traditionally.   All in all, with an on-delay timer, timing begins when voltage is applied. When the time has expired, the contacts close — and remain closed until voltage is removed from the coil.   Time delay relays circuit and working     See the above circuit diagram, time delay relay circuit contains an electromechanical relay and driver circuit, this circuit decides the time delay to give power supply to the electromechanical relay coil by the way to the load connected to the relay.   This circuit is divided into two sections. The first section is time delay elements such as voltage divider resistor series and two electrolytic capacitors. The second section is a relay with an indicator LED. Resistor R1, potentiometer, and R2 connected in series and across to the DC input supply, the output of the variable resistor (potentiometer) is connected to the C1 capacitor and reverse-biased Zener diode then C2 capacitor finally to the base of transistor SL100. 12V Relay is connected with the collector terminal of SL100 transistor and Bicolor LED terminal green is connected with the emitter of Q1 and terminal Red is connected across collector.   When the supply given to this circuit depends on the value of the Potentiometer small level voltage passed to C1 and it gets charged when its completed and above the cutoff limit of the Zener diode, Voltage passed to the C2 capacitor and it gets charge, finally the base-emitter voltage limit of Q1 transistor reached by the C2 then Q1 gets turn ON and Relay coil gets complete DC supply then Relay energized for to complete the above process it takes some time delay depends on Potentiometer value, C1-C2 charge time and Zener diode breakdown voltage hence we can achieve few seconds to few minutes time delay.   By changing the Potentiometer value or C1-C2 value we can achieve different time delay levels. We can use this circuit to turn ON or turn OFF some sensitive time delay required electrical applications.     How to select a delay relay? Selecting a relay, there are many factors that need to consider including data on thermal,motor-driven, pneumatic, RC, slugged, hydraulic, escapement, and solid-state types.   The fantastic growth of the field of automatic industrial control has increased the demand for new and more versatile devices to perform the basic electrical switching functions required. The use of time-delay relays has grown rapidly to keep pace with the demand for the basic function which they can perform: that of obtaining a predetermined delay from one switch operation to another.     (A) Delay on energization. (B) Delay on de-energization. Time-delay relays perform in a manner quite similar to a standard relay in that they have contacts that open and close when power is applied and removed from the input terminals. The basic difference is that a delay is incorporated into the contact opening or dosing. Time-delay relays are used in a wide range of applications: from determining how full your coffee cup will be when you put a dime in a vending machine, to shutting off the cutting oil on a milling machine. The most popular time-delay relay is the delay on operation, or de-energization, in which the normally open load switching contacts transfer at a predetermined time after power is applied to the input. The contacts drop out immediately upon the removal of the input power   Often a time delay on release, or de-energization, is required. In this case, the normally open load switching contacts operate immediately when the input power is applied and remain in this position as long as the input power remains "on". Upon removal of this power the timing begins, and after a predetermined delay, the contacts drop out. Several variations on these two basic timing modes are used, such as interval "on", automatic recycle, combined "on" and "off" timers, and sequence timers. Many of these can be made by simple connections of the two basic types.   FAQ   1. What is Relay and its uses? Relays are switches that open and close circuits electromechanically or electronically. Relays control one electrical circuit by opening and closing contacts in another circuit. ... In addition, relays are also widely used to switch starting coils, heating elements, pilot lights and audible alarms.   2. What is the relay device? Relay is an asynchronous, screen-free walkie talkie system that allows parents to stay in touch with their kids at the push of a button. Relay is a Republic Wireless product, and makes use of the carrier's cell phone network (via T-Mobile and Sprint).    3. What is Relay and its types? Relays are electrically operated switches. They are used to control a circuit by a separate low-power signal or to control several circuits with one signal. ... The three main types of relays are electromechanical, solid-state, and reed. This overload protection relay reacts to overheating.   4. What is the working principle of relay? Relay works on the principle of electromagnetic induction. When the electromagnet is applied with some current it induces a magnetic field around it. Above image shows working of the relay . A switch is used to apply DC current to the load.   5. Does relay important? Converting a small electrical input into a high-current output is no easy feat, but this task is necessary to efficiently operate a wide range of standard appliances and vehicles. Many circuits achieve these conversions through the use of relays, which are indispensable in all kinds of electronic equipment.   6. What are the 5 applications of relay? Applications of Relays in Electronic Circuits: Relay Drive by Means of a Transistor. Relay Drive by Means of SCR. Relay Drive from External Contacts. LED Series and Parallel Connections. Electronic Circuit Drive by Means of a Relay. Power Source Circuit. PC Board Design Considerations. 7. What is difference between relay and circuit breaker? The Relay is a switching and sensing device, but the Circuit breaker is an isolating or disconnecting device. Relays operate on low power input voltage. ... The Relay is used to control or select one among many circuits, whereas Circuit Breaker is one per circuit. Relay acts an electrical amplifier for discrete signal.   8. How fast can a relay switch? 5 to 15 ms. While the mechanical construction of electromechanical relays allows for much flexibility in switching capability, they have one important limitation: speed. When compared to other relays, electromechanical relays are relatively slow devices -- typical models can switch and settle in 5 to 15 ms.   9. Why do I need a relay for LED lights? Relays can be used to switch a low-current trigger to high current, switch a circuit on or off, reverse polarity, and much more. When adding LED lights, such as off-road light bars, driving/work lights, or other auxiliary lights to a vehicle, you must add a circuit to power the light adequately.   10. What is the major application of relays in our daily lives? The typical applications of electromechanical relays include motor control, automotive applications such as an electrical fuel pump, industrial applications where control of high voltages and currents is intended, controlling large power loads, and so on.   You May Also Like: Making a Arduino Variable Timer Relay How to Drive Thermostat by Using Solid State Relay Product Recommendation: CMRD6055 CB-1001B-70 G6K-2F-Y-TR DC24

The global lamp market has undergone tremedous changes over the last several years. Even government regulation,declining packaged LED and other component prices, and technological advancements have all played a major role in the continued penetration of LED into the overall market. Obvioulsy, LED lamps are the future of lighting, and there is a new invention using LEDs has been pushing out that Osram,a lighting company that offers innovative and sustainable lighting solutions, has revealed that he will stitch LEDs into workwear.  About this amazing news,Osram has taken a first step toward weaving smart lighting into clothes, announcing workwear that lights up with LEDs, while strongly hinting that interactive apparel is coming including a cycling jacket that illuminates when you hit the brakes, and lights that flash when your pulse rate rises too high. At the same time,Osram decided to stitching LEDs into safety vests and work jackets,and choosing Fvrth,a Germany-based safety and sportswear company uvex to operate with.Osram's first stab at textile illumination stops short of interactivity. It simply focuses on giving visibility to workers on job sites. “The textile illumination is incorporated into the safety clothing and ensures greater visibility and hence safety in day-to-day work, for example, on construction sites or in road traffic,” Osram said. “The key advantage of the new technology: Reflector strips on conventional work clothing only reflect incident light, while the light modules ensure active illumination at all times, thus improving safety when working in the dark or in poor visibility conditions.” Osram has been testing the technology for some time.The company used it to help illuminate ice hockey players, sticks, and pucks in an outdoor night game nearly10,000 ft high in the German Alps last year, for example. With sportswear as part of the mix, Osram plans to eventually add sensors that will enable integrated LEDs to respond to physical stimuli, providing health alerts, safety measures, and more.“This will in the future allow various applications to be controlled using an app,” Osram said. “Possible examples include sports clothing that warns the wearer about a high pulse rate via the light guides, or a cycling jacket with an integrated brake light.” Like many lighting companies, Osram is trying to establish LED lights and luminaires as nodes and backbones of information technology networks.While some industry observers expect that one day, OLED technology will prevail for integrated textile illumination, Osram has chosen instead to stitch LEDs, as have other illuminated clothing providers. OLED (organic light-emitting diode) is a patch of material that emits light in response to a current, whereas LEDs are single light points. Osram told LEDs Magazine that it has no plans to use OLEDs for lighting textiles. 

In autumn, an abundance of fallen leaves from deciduous phoenix trees are scattered around the streets in Northern China. These leaves are generally burned in the colder season, exacerbating the country's air pollution problem.Investigators in Shandong, China, recently discovered a new method to convert this organic waste matter into a porous carbon material that can be used to produce high-tech electronics. The advance is reported in the Journal of Renewable and Sustainable Energy, by AIP Publishing. The investigators used a multistep, yet simple, process to convert tree leaves into a form that could be incorporated into electrodes as active materials. The dried leaves were first ground into a powder, then heated to 220 degrees Celsius for 12 hours. This produced a powder composed of tiny carbon microspheres. These microspheres were then treated with a solution of potassium hydroxide and heated by increasing the temperature in a series of jumps from 450 to 800 C. The chemical treatment corrodes the surface of the carbon microspheres, making them extremely porous. The final product, a black carbon powder, has a very high surface area due to the presence of many tiny pores that have been chemically etched on the surface of the microspheres. The high surface area gives the final product its extraordinary electrical properties.(Scanning Electron Microscopy (SEM) image of porous carbon microspheres.)The investigators ran a series of standard electrochemical tests on the porous microspheres to quantify their potential for use in electronic devices. The current-voltage curves for these materials indicate that the substance could make an excellent capacitor. Further tests show that the materials are, in fact, supercapacitors, with specific capacitances of 367 Farads/gram, which are over three times higher than values seen in some graphene supercapacitors. A capacitor is a widely used electrical component that stores energy by holding a charge on two conductors, separated from each other by an insulator. Supercapacitors can typically store 10-100 times as much energy as an ordinary capacitor, and can accept and deliver charges much faster than a typical rechargeable battery. For these reasons, supercapacitive materials hold great promise for a wide variety of energy storage needs, particularly in computer technology and hybrid or electric vehicles. This research is led by Hongfang Ma of Qilu University of Technology, and has been heavily focused on looking for ways to convert waste biomass into porous carbon materials that can be used in energy storage technology. In addition to tree leaves, the team and others have successfully converted potato waste, corn straw, pine wood, rice straw and other agricultural wastes into carbon electrode materials. Professor Ma and her colleagues hope to improve even further on the electrochemical properties of porous carbon materials by optimizing the preparation process and allowing for doping or modification of the raw materials. The supercapacitive properties of the porous carbon microspheres made from phoenix tree leaves are higher than those reported for carbon powders derived from other biowaste materials. The fine scale porous structure seems to be key to this property, since it facilitates contact between electrolyte ions and the surface of the carbon spheres, as well as enhancing ion transfer and diffusion on the carbon surface. The investigators hope to improve even further on these electrochemical properties by optimizing their process and allowing for doping or modification of the raw materials.  This article is authored by Hongfang Ma, Zhibao Liu, Xiaodan Wang and Rongyan Jiang and is published in Journal of Renewable and Sustainable Energy.  Ref.KY36-5KK560KOAAM(capacitor)KY36-DEBB33F222KA3B(capacitor)KY605-NH12VP(rechargeable battery)  

The rapid development of wearable technology has received another boost from a new development using graphene for printed electronic devices. New research from The University of Manchester has demonstrated flexible battery-like devices printed directly on to textiles using a simple screen-printing technique. The current hurdle with wearable technology is how to power devices without the need for cumbersome battery packs. Devices known as supercapacitors are one way to achieve this. A supercapacitor acts similarly to a battery but allows for rapid charging which can fully charge devices in seconds. Now a solid-state flexible supercapacitor device has been demonstrated by using conductive graphene-oxide ink to print onto cotton fabric. As reported in the journal 2D Materials the printed electrodes exhibited excellent mechanical stability due to the strong interaction between the ink and textile substrate. Further development of graphene-oxide printed supercapacitors could turn the vast potential of wearable technology into the norm. High-performance sportswear that monitors performance, embedded health-monitoring devices, lightweight military gear, new classes of mobile communication devices and even wearable computers are just some of the applications that could become available following further research and development. To power these new wearable devices, the energy storage system must have reasonable mechanical flexibility in addition to high energy and power density, good operational safety, long cycling life and be low cost. Dr Nazmul Karim, Knowledge Exchange Fellow, the National Graphene Institute and co-author of the paper said: "The development of graphene-based flexible textile supercapacitor using a simple and scalable printing technique is a significant step towards realising multifunctional next generation wearable e-textiles." "It will open up possibilities of making an environmental friendly and cost-effective smart e-textile that can store energy and monitor human activity and physiological condition at the same time". Graphene-oxide is a form of graphene which can be produced relatively cheaply in an ink-like solution. This solution can be applied to textiles to create supercapacitors which become part of the fabric itself. Dr Amor Abdelkader, also co-author of the paper said: "Textiles are some of the most flexible substrates, and for the first time, we printed a stable device that can store energy and be as flexible as cotton. "The device is also washable, which makes it practically possible to use it for the future smart clothes. We believe this work will open the door for printing other types of devices on textile using 2D-materials inks." The University of Manchester is currently completing the construction of its second major graphene facility to complement the National Graphene Institute (NGI). Set to be completed 2018, the £60m Graphene Engineering Innovation Centre (GEIC) will be an international research and technology facility. The GEIC will offer the UK the unique opportunity to establish a leading role in graphene and related 2D materials. The GEIC will be primarily industry-led and focus on pilot production and characterisation. Ref.MS614SE-FL28EML-614S/FN

A safety monitoring method called On-Site Visualization has been implemented in metro system construction sites in Jakarta, Indonesia as part of a Japan International Cooperation Agency (JICA) project. On-Site Visualization (OSV), as its name suggests, is a real-time data processing technology used to check safety levels at construction sites. A device with built-in LEDs is attached to walls and pillars at the building site and measures any irregularities or tilting. The LEDs light up like traffic lights to indicate the danger level with different colors: blue for "no irregularities", and yellow and red for "danger of collapse". This clear method of representation is important in countries with low literacy rates.The JICA project, titled Economic and Social Development Support in Developing Countries through Partnerships with the Private Sector, had participants from multiple private organizations in the OSV Consortium (an industry-academic collaborative group that promotes use of OSV technology). Professor Akutagawa oversaw the technology use. The teams monitored safety levels using OSV for a fixed period at three metro system building sites in the center of Jakarta (two stations in the city center and an elevated track in the south). Following this, they held a seminar presenting the results of the implementation. The project was evaluated highly by the head of construction at Jakarta MRT, who stated that "We can now expect higher standards of safety management".In many developing countries, an increase in public works is accompanied by a sharp rise in the number of accidents, and there is a growing need for safety monitoring. "I want to build a human network that combines know-how from different fields to improve levels of safety and security" commented Professor Akutagawa.Reference:LM324MMLM2710LM3080 

IBM today introduced the fifth generation of semiconductor technology specialized for high performance communications. The company's latest silicon-germanium (SiGe) chip-making process is designed to enable ever-increasing amounts of data to flow through network backbones in applications such as Wi-Fi, LTE cellular, wireless backhaul and high speed optical communications.Since its introduction in 1995, IBM's SiGe semiconductor technology has helped spur a revolution in radio frequency (RF) performance, enabling engineers to develop breakthrough devices such as satellite global positioning systems, WiFi radios and high speed optical links. IBM's new "9HP" SiGe technology continues to put advanced capability in the hands of engineers who design chips for LTE cellular base stations, millimeter-wave wireless communication links, and next generation short and long-haul optical communications. Outside of communications, 9HP performance will advance the state of the art in other applications such as high-performance test equipment, automotive radar and security imaging."Silicon-germanium is one of the key technologies that have enabled wireless operators to keep up with the explosive growth in data traffic generated from mobile handsets," said David Harame, IBM Fellow. "Before SiGe, the high-performance chips used in base stations and optical links were built using expensive, esoteric processes. SiGe provides the necessary performance as well as integration and cost savings via its CMOS base."Open Collaboration is Key to SuccessOver the years, a number of leading technology companies have come to rely on the benefits and advantages of SiGe, working closely with IBM to develop and refine new versions of the chip-making process. IBM believes that open collaboration among companies will drive future breakthrough innovation in semiconductors."As early adopters of IBM's SiGe technology, Semtech has consistently pushed the envelope on what can be achieved in high-speed wired and wireless communications systems and in high performance analog devices," said Charles Harper, Senior Vice President of Semtech's Systems Innovation Group. "With today's technology, Semtech is a leader in 40Gbps and 100Gbps Communications Systems and with IBM's latest SiGe technology we believe we can emerge as a leader in several new analog segments where performance, integration and power are critical requirements.""Our long collaboration with IBM on SiGe technology has enabled Tektronix to break new barriers on what can be achieved in high-fidelity, high-bandwidth oscilloscopes," said Kevin Ilcisin, chief technology officer, Tektronix. "We utilized IBM's SiGe 9HP for our patent-pending asynchronous interleaving approach, and expect to break new ground by providing customers bandwidth capabilities of 70 GHz and beyond while significantly improving our signal-to-noise ratio."Key Technology Details, Specs9HP will be the first SiGe technology in the industry featuring the density of 90nm CMOS which will enable the highest level of integration in a fully production qualified SiGe BiCMOS technology. IBM's new SiGe BiCMOS technology delivers higher performance, lower power and higher levels of integration than current 180nm or 130nm SiGe offerings.The technology maintains compatibility with IBM's 90nm low power CMOS technology platform, enabling foundry clients to port a wide range of intellectual property circuit blocks and standard cell library elements. The 90nm foundry platform also includes an RF CMOS technology option, giving IBM foundry customers a broad range of technology choices for RF and mixed-signal applications.Additional technical specifics include:90nm Lithography based SiGe BiCMOSAdvanced SiGe HBT NPNs, Ft = 300GHz, Fmax > 350GHz90nm CMOS FETs, 1.5, 2.5v/3.3vThick Dielectric Add-On Modules – Low-K, Cu, AlFull Suite of Passives-Resistors, Varactors, MOS and MIM Capacitors, High Q Inductors, mmWave elementsPIN and THz Schottky Barrier DiodesProcess Design Kits featuring precision RF device models