What is a switch relay
It is an electronic control component that adopts the function of controlling a big current circuit on or off through a coil with a small current. It is mainly made up of coils, iron cores, armatures, contacts, and other components. Powered on, the coil will surely produce a magnetic effect, attract the armature to move, and then push the contacts to close or open for the purpose of switch control of the circuit. It finds application in all walks of life, from automotive and industrial control to household appliances. The advantages to be accrued from using relays include precision, high reliability, and attainment of automation control.
relay element
Coil: The most basic part of a relay is the coil, which in fact is a type of electromagnet. As soon as it becomes energized, it will generate a powerful magnetic field. Usually, coils are made by tightening wires around a magnetic core, which is typically a wire spool or ferromagnetic material that aims at raising the magnetic field effect.
Contact: It is a touchy electric terminal that obstructs or controls current flow in a circuit. Based on the design of the relay, they can be in a normally open condition, a normally closed condition, or may have a switching function.
Armature: It is that part of a relay that is moved by the magnetic action of a coil, and whose movement changes the state of the contacts.
Yoke: A yoke is a metal frame that surrounds a coil completely to provide full path for the magnetic field for its stability and effectiveness.
Iron core: Although part of the coil, it forms part of the magnetic circuit, where the magnetic fields are enhanced and conducted.
Shell: The shell is basically a layer of protection on the relay; it wraps tightly on the internal parts inside it. As a result of this, even at really extreme environments, the relay could work perfectly.
Terminal: The terminal is used to connect the relay to an outside circuit, and with the help of a terminal, the relay can be easily connected to the circuit.
Spring: The spring plays a dual role in a relay: first, keeping the contacts in a certain position so as to keep the circuit stable; second, it returns the armature to its original position quickly if needed and thus achieves the rapid switch of contacts.
Diode: Several relays have inbuilt diodes that are designed in order to protect the coil from large voltage spikes, which may take place at the time of opening the contacts. This extends the service life of the relay.
Relay 3D Structure Diagram
Switch relay type
I have done classification and selection for most of the relays in the market here. Before that, they had different functional features; let me introduce them one by one below.
It is the most traditional and widely used form of relay. The core component is the electromagnet, which will generate a magnetic field to attract and drive the mechanical switch when turning on to actuate and change the state of a circuit. This kind of relay boasts characteristics of stability and reliability, has fast action, and is fit for various electrical control systems.
The solid state relays take advantage of advanced semiconductor technologies such as the transistor or thyristor to replace the traditional electromagnet and mechanical switch. This type of relay is very suitable for high-frequency and high-precision control because of its contactless, noise-free, fast response speed, and longevity.
reed relay
Reed relay is a type of electromechanical relay containing single or multiple reed switches inside small glass or plastic tubes. Under the magnetic field's action, the spring will deform, thus changing the state of the circuit. This kind of relay has advantages such as small size, high sensitivity, and good sealing, mainly used in the design of compact circuits.
These delay relays can introduce timing delay between the input and output signals for circuit delay control. Normally, such relays have adjustable delay time and are suitable for use in those places where exact control of the time intervals is needed, like timers, sequence controllers, etc.
Latch relay
The latching relay has a self-locking function which can maintain its output state unchanged in case of power-off state. Normally, this type of relay is locked by mechanical or electrical means. It is applicable for such situation that requires stability of the circuit, for example, memory circuit, safety control system, etc.
Overload relay
Overload Relay Catalog It is used to protectively monitor the current change of the circuit and cut off the circuit when the current exceeds the set value in order to avoid damage to the circuit and device resulting from overload or short circuit. The relays feature high sensitivity and powerful reliability, which forms the essential guarantee of safety in the electrical system. We call it the thermal relay.
Thermal relay
It is used for circuit protection and is typically designed to monitor thermal changes in circuits and provide switch action when the temperature exceeds a predetermined value. This type of relay typically includes temperature sensing elements and contact switches, suitable for applications that require temperature monitoring and protection, such as overheating protection for equipment such as motors and transformers.
Control relay
Control relays are mainly used to guide other devices to control actions. It usually consists of multiple contact outputs, which can achieve complex logic control functions. This type of relay is widely used in a series of electrical control systems, including contactors, motor starters, etc.
Plug in relay
Plug in relay is a type of relay that is very easy to install and replace. It usually has standardized dimensions and interfaces, making it easy to insert into control panels or switch devices. This type of relay is suitable for situations that require frequent replacement or maintenance, such as in industrial production lines or automation equipment.
Characteristics of switch relays
The properties of relays do vary with type and design, but the following are the general features applicable to most relays universally, and they shall be explained here, which become necessary while understanding and choosing the right relay:
Switching Capacity
It is the maximum value of current and voltage which the relay can sustain and handle. If these limits are exceeded, it may lead to damage or deterioration in the performance of the relay.
Contact Resistance
Contact resistance is the level of interference to current flow caused by relay contacts when the relay contacts are closed. In applications where high currents need to be handled, it will be better if the contact resistance is low to keep energy losses and heat generation at low levels.
Operating Bounce Time
Bounce time is the short-time unstable situation of a relay contact either due to mechanical or electromagnetic reasons after closing or opening until it finally reaches stability. In the case of high-speed switching applications, bounce time becomes a very important parameter as it may really deteriorate the performance and stability of the system.
Operating time
It defines the time required from the moment the coil starts to be turned on or off up until when the relay contacts are fully closed or opened. This parameter is very important for systems requiring precision in timing control.
Release time
Release time: It is the time the contacts of a relay take to move from a completely closed position to a fully open position after the coil is de-energized or turned off. This too is a vital aspect for systems that require response in the minimum possible time.
Expected life span
Expected life denotes how many operations can be done by a relay before a failure happens, sometimes it is also named as mechanical life or electrical life. This parameter is important for judgment of the reliability and long-time running ability of relays.
Insulation resistance
It mainly refers to the resistance value between relay coils and contacts and among different circuit parts. High insulation resistance can avoid the leakage and discharge of unnecessary currents to ensure the safety of the system and personnel.
Dielectric Strength
Dielectric strength is the value of high voltage that a relay can bear without damage. This parameter is very important for ensuring the reliability of relays operating under high voltage conditions.
Ambient Temperature
The ambient temperature is the amount of temperature within which the relay can operate normally. Certain applications in some cases require certain environmental conditions like extreme temperature operation for which relays are designed.
Shock and Vibration
Shock and Vibration: refers to the performance of a relay maintaining performance and structure against mechanical shock and vibration. Impact resistance and vibration performance are important when relays are used in harsh environments like industry or automobiles. The relays shall be selected by proper rating in vibration and shock resistance.
Switch relay wiring
That is different for different relay types. It usuably covers wiring for the following:
Coil wiring
1. Determination of voltage of the coil: First of all, find out what the relay coil operates on in terms of voltage. There are commonly three types: DC 12V, 24V, and AC voltage coils.
2. Connect the power supply: Line the positive and negative poles of the power supply with the two pins of the relay coil according to the coil's voltage requirement. Generally speaking, coil pins are labeled with symbols or numbers such as "+" and "-". When connecting, be careful not to reverse the polarity of the positive and negative poles; otherwise, the coil will not work properly.
Connect the contactor
Normally open contact: Normally, this contact of the relay is in an open state when the relay is at a non-activated stage. The application of electromotive force to the relay coil will change the state and make the normally open contacts close. Normally open contacts are used very often in a control circuit to connect some other circuits under particular conditions. One side of the load to be controlled is then connected to one pin of the normally open contact, while the other side of the load connects to the power supply or other circuit components.
Normally closed contacts: normally closed contacts are those which by default close when the relay is at an unpowered state. In this case, normally closed contacts will disconnect when the coil in the relay is energized. Normally closed contacts can also be applied in the disconnecting circuit under some conditions. The wiring method is almost similar to that of normally open contact, which connects the load to the pins of normally closed contacts again.
Common contact : Normally open contact and normally closed contact share a pin, which is called common contact. The common contact will be connected to a normally open contact or a normally closed contact according to different action states of the relay. The common contacts shall be connected to the relevant part in the circuit according to needs in the process of wiring.
How to choose a switch relay
Choosing the proper relay is extremely important to ensure either an electrical system or equipment works normally. The explanation for what you have listed is as follows, and it shall also help in making informed choices:
Voltage and current ratings
Rated voltage and current mean the maximum limits within which the operation of a relay is assured to be safe. In selection, it is usually necessary to ensure that the rated value of the relay should at least be equal to or greater than the actual operating voltage and current in the circuit so as not to overload and damage the relay.
Switching capacity
The switching capacity of the relay is given by the maximum load it can handle, including current, voltage, and power. Ensure that the switching capacity of the relay is big enough to handle load fluctuation and transient overloads.
Contact method
Choose relays according to the number and type of contacts required to satisfy the control circuit. NO: Normally open-open when not energized; NC: Normally closed-closed when not energized; CO: Transition-contact device, both NO and NC. The transition-contact device can be either NO or NC.
Expected Useful Life
The life of a relay service is usually estimated in terms of the number of operations, or mechanical/electrical lifetime. For high cycles, long-life relay selection can be done which will reduce maintenance/replacement frequency.
Operating time and release time
Actuating period is the time taken by the relay to be energized and the contacts to close or open completely; this is usually expressed in milliseconds. The release period is the time taken by the relay to power off and by the contacts to open completely. Choose relays whose action and release times are suitable for applications.
Installation
The relay must be easy to install at the location against which it has been put into application. The location might either be on a circuit board or on a panel. This of course is taking into account the size of the relay, installation method as well as any accessory required in the process of installation.
Standard
Select relays that meet the relevant industrial standards, such as but not limited to UL, CSA, VDE, CE, etc. Such standards mean that the safety and performance of the relays meet the requirements accepted internationally.
Cost
In relation to the cost of relays versus meeting performance requirements, compare prices among different brands and models to arrive at the product with the highest value.
Brand reputation
Choose the well-known brand QIANJI, which has been a supplier of switch relays for over 20 years and has its own core competitiveness. And accumulated a good reputation. Provide higher quality products and better service support, including warranty and after-sales service.
summarize
Choosing the appropriate relay requires comprehensive consideration of multiple factors. By carefully comparing the performance, price, and service of different products. QIANJI provides you with the perfect relay solution
How to test relays
There are several ways in total to test whether the relay is working or not. The basic methods provided herein are quite effective and have been commonly adopted. Here are explanations in detail, and some additional precautions for these methods.
Visual Inspection
First of all, visual inspection is the first step in the test of a relay. By observing carefully, the obvious damage or defect on the appearance of the relay can be found, such as contact broken, burning, coil breakage, or shell rupture.
During visual inspection, the first thing to ensure is that the relay is at an power-off state to avoid the risk of electric shock.
Ohmmeter test
An ohmmeter is a simple, effective way of testing resistance in the coils of relays. After switching off the power, hook up the ohmmeter on the coil terminal of the relay and look for the reading.
A good relay coil should have a low reading, which implies that it is intact and not open circuited. If the reading were to show 'infinite' or very high resistance, this would indicate that the coil may be open or damaged.
Continuity testing
Continuity testing is applied to the continuity of relay contacts. After the power is switched off and the relay disconnected from the circuit, the continuity between the common terminal and NO/NC terminal should be tested either by a continuity tester or a multimeter.
For instance, if the test shows that there is discontinuity between the contacts, then the contacts are either damaged or dirty, hence the relay has to be cleaned or replaced.
Power test
A power test is carried out when the relay is powered up. Connect the relay to the circuit and switch it on, then check for voltage across the coil at both ends.
If voltage is present but the relay fails to pull in, internally, the fault may be in coil breakage, contact adhesion, or a mechanical failure in the relay.
Operation Testing
The testing of operation is the last procedure to confirm whether the operation of the relay is properly performed. For every control circuit ON/OFF action, it should be connected with the circuit and power on to see whether the relay connects and disconnects or not.
The failure of the control circuit, internal failure in the relay, or power problems might be some possible reasons.
Application of switch relay
Automobiles and Trucks: These are also highly used in automobile and truck construction; examples include lighting, fuel injection, ignition, and power windows.
Industrial control: The relay systems also find their use in industrial control, related to the control of motors, processes, and temperatures.
Communication: Relays are utilized in telephone exchanges and other telecommunications equipment for the purpose of switching and signal routing.
Household Appliances: The equipment in the class of household appliances, such as refrigerators, washing machines, and air conditioners, employ relays for controlling motors as well as other accessories.
Computers and related Electronics: In computers and other electronic appliances, the relays perform functions like switching and routing of signals besides controlling the power feeding to different components.
Contact QIANJI immediately to experience high-quality manufacturing,
Fast turnaround time and excellent customer service.
Contact us for a quote and start your next project!
However, do you need any help? Contact Us: Providing You with the Most Thoughtful Service
label:a switching relay has the following characteristics,Switching relay