Relay how does it work

What Is a Relay? Why Use a Relay? Switching Level of Current One of the most common situations that require the use of a relay occurs when an application needs to switch from high to low current or vice versa within the same circuit.

Complex Applications Relays are not limited to transforming single inputs into single outputs at single points in the circuit. How Does a Relay Work? Normally Open Relays Most relays are normally open; that is, the second, larger circuit is in the off position by default. Normally Closed Relays The fundamentals of an NC relay are the same as an NO relay: there are two circuits, with the second being larger, and an electromagnet moves a physical contact between two positions.

How to Identify a Faulty Relay Though generally reliable, relays can fail like any mechanical component. Use the following troubleshooting steps: Check for voltage at the point where the relay plugs in. If there is none, check the fuse or switch for defects. If there is voltage at the connection point, use the continuity function on the multimeter to ensure a good ground connection on the opposite side of the relay.

If Steps 1 and 2 do not reveal the source of the problem, check the voltage at the point where the relay connects to the battery or other power source. If there is no voltage here, there may be a problem with a fuse or circuit breaker. Finally, ensure that a proper connection exists between the relay and the component by using the continuity function of the multimeter.

If the connection exists, and if the prior steps did not suggest another malfunction, then it may be time to replace the relay. Types of Relays Many types of relays exist, each bringing unique functions to a variety of applications. Some of the broader categories include: Time-Delay Relays Time-delay relays are useful in any situation that requires components to be powered for a set length of time, or when the component must power on or off after a specific delay.

Most time-delay relays can be sorted into one of two broad categories: On-delay timers begin timing when the input is applied, powering the second circuit after a set wait time. View Order Download. Type the QR Code below to view a datasheet.

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Why Use a Relay? Why Use a Relay in a Car? A relay is an electrically operated switch. They commonly use an electromagnet coil to operate their internal mechanical switching mechanism contacts. When a relay contact is open, this will switch power ON for a circuit when the coil is activated. The example relay diagrams below show how a relay works. Why use a Relay? Relays allow a low current circuit to control one or more higher current circuits. Then, current will be blocked when the relay is in off state and allows the current when a control signal is triggered.

Uses microprocessor type relays for switching purposes. The electrical faults are detected using software testing algorithms and diagnostics communication etc. The microprocessor detects over voltage and current, frequencies, ground faults, excitation loss of power etc. Check in the datasheet. This is the best way to inspect relay pins and their connections. The datasheet will contain current and voltage ratings which will help to use the relay without damaging. The relay details are provided on the body itself.

Check the relay physically. Modern switches come up with LED. When the relay is present in an active state, the LED will glow and it will make a click sound. In de-energized condition, check the resistance between the NO terminals, it should be infinite ohms practically in Mega Ohms. And, the resistance between the NC terminals should be zero ohms. Now, apply the required voltage to energize the relay.

Here are some of the important applications of relay that are used in automation, energy, smart grid, telecom, and power industries. In short, Electronic overload relays are essential protection components for over current and current sensitive applications such as motor overloads, high inrush currents and stalled motor problems.

Moreover, they are helpful in monitoring electrical parameters like temperature, line currents, power factor and residual currents. Other than general purpose ones, HVAC relays for fan switching , Time delay relays for flashlight control, self start control in bikes and cars engines, automatic timing control etc , liquid level control relays have resistance detection circuit that senses condensation levels in a tank. SPDT Switch. DPST Switch.

The movable armature is connected to the yoke which is mechanically connected to the switch point contacts. These parts are safely held with the help of a spring.

The spring is used so as to produce an air gap in the circuit when the relay becomes de-energized. The relay function can be better understood by explaining the following diagram given below. The diagram shows an inner section diagram of a relay. An iron core is surrounded by a control coil. As shown, the power source is given to the electromagnet through a control switch and through contacts to the load.

When current starts flowing through the control coil, the electromagnet starts energizing and thus intensifies the magnetic field. Thus the upper contact arm starts to be attracted to the lower fixed arm and thus closes the contacts causing a short circuit for the power to the load.

On the other hand, if the relay was already de-energized when the contacts were closed, then the contact move oppositely and make an open circuit. As soon as the coil current is off, the movable armature will be returned by a force back to its initial position. This force will be almost equal to half the strength of the magnetic force.

This force is mainly provided by two factors. They are the spring and also gravity. Relays are mainly made for two basic operations. One is low voltage application and the other is high voltage. For low voltage applications, more preference will be given to reduce the noise of the whole circuit.

For high voltage applications, they are mainly designed to reduce a phenomenon called arcing. The basics for all the relays are the same. Take a look at a 4 — pin relay shown below. There are two colours shown. The green colour represents the control circuit and the red colour represents the load circuit. A small control coil is connected onto the control circuit. A switch is connected to the load.

This switch is controlled by the coil in the control circuit. Now let us take the different steps that occour in a relay. As shown in the circuit, the current flowing through the coils represented by pins 1 and 3 causes a magnetic field to be aroused.

This magnetic field causes the closing of the pins 2 and 4.