Then my installing relays at critical points the remainder of the circuit can be completed with more inexpensive low current components. This helps drive costs down. Everybody's happy! An electro-magnetic relay is constructed of a coil of wire that is wrapped around a soft iron core - known as a solenoid. It has a movable iron armature, a low reluctance iron yoke and a set of contacts. There can be multiple sets of contacts depending on the design and function of the relay.
The yoke has a hinged armature attached which is linked to the movable contacts. A spring holds the armature in position and when the relay is de-energised an air gap in the magnetic circuit is created. This condition delivers the the physical closing and opening of contacts. In an automotive relay with two contacts this would mean that one contact is opened while the other is closed. When an electric current is delivered to the solenoid a magnetic field is generated.
This field triggers the armature and the resultant movement of the contacts either makes or breaks the circuit. A make and break relay has four pin terminals and a single high current circuit. The contact in a make or break relay is either normally open NO , or normally closed NC.
The open or closed position of the relay depends on its design and controlled by whether the relay is at rest or energised. A normally open relay, NO , at rest has a broken contact - it's open. The reverse is true for a normally closed, NC , relay. A normally closed relay at rest has a closed contact.
Typically the relay is switched manually using push or toggle switch - an everyday example of this is the car ignition switch used to start the engine. A changeover relay is built with two circuits instead of one and five pins rather than four. Instead of making and breaking a single high voltage circuit it alternates the closing and opening of two circuits - 'changing over' which circuit is open or closed.
A typical example of a change-over relay in use can be seen in the operation of vehicle headlights. The relay can switch between circuits to activate the full beam or dipped beam as required. Another everyday example is the car air-conditioning system. One or the other will be running and never both at the same time. Changeover relays are sometimes referred to as Single Pole Double Throw relays. The terminals of a relay are numbered using an identification system known as DIN This system was developed in the German automotive industry and has since been adopted across the world as the standard method for labelling and identifying electrical terminals.
The table below shows the codes used in automotive relays. Some automotive relays are designed with diodes or resistors built in. These devices help suppress coil voltage spikes and protect the electronic circuit.
When the voltage is removed and a relay is denergised the magnetic field collapses. This can result in a voltage surge in the opposite direction. These low current surges can have significantly high voltages, often up to volts. A potted relay is a special relay that functions like other types of relays. Its difference with others is that its bottom part is sealed with an epoxy to ensure water cannot penetrate inside.
The limitation of the potted relay is that it cannot be repaired. Read more: Understanding the working of magneto ignition system. Led types of flashers are electrically controlled by a small solid-state integrated circuit I. Well, several connected lights do not affect its output.
Duration of current flow can also be adjected from as little as 2sec to as long as 3min after power is switched off to the coil. These types of relays contain a solid-state timing circuit with a variable resistor that controls the time delay effect. A time delay relay is commonly used for powering vehicles parking lights for an extended time after the vehicle is exit so that you around the vehicle.
Flasher relay has two or three pins, unlike the standard relays that have four to five pins. In a two-pin flasher, one pin is connected to power and the other to the light circuit. While three-pin flasher with an addition pin that would be connected to an indicator light that lets the user know flasher is on. Not all flashers relay actually operate as a relay, some act more like a circuit breaker. But they are still group as relays.
Most flasher relays are thermally controlled like a circuit breaker. Current flows through the coil of the flasher relay create enough heat. This heat causes the contacts inside the relay to deflect causing the contacts to open and stop the current flow.
Once enough heat has dispelled, the contacts will return to their original position and a current will flow again. Well, numbers of light connected to a thermal flasher will determine its output performance. Electromechanical flashers work with a circuit board that contains a capacitor, a couple of diodes, and a coil to create the same flash pattern as a standard flasher.
These types of flasher relays are capable of handling higher loads with improved performance over thermal flashers. The numbers of light connected to these types of flashers have less effect on its output. Wig-wag types of flasher are also known as alternating flashers that uses a solid-state flash circuit. This circuit helps to alternate between two separate lamp circuits.
Skirted types of relays have an extended skirt around its bottom to seal around a socket. This avoids water and contaminants from entering the relay contacts.
These relays are often used in exposed areas of automotive. Read more: Understanding the working of electronic ignition system. The purpose of an automotive relay is to automate this power to switch electrical circuits on and off at particular times. However, the real benefit behind a relay is more than just automation; they also provide the ability to switch multiple circuits , including different voltage types, within the same relay at the same time. If you were to open a relay, you would see an electromagnet coil, the switch, and a spring.
The spring holds the switch in position until a current gets passed through the coil. The coil then generates the magnetic field which moves the switch on and off. Looking at the diagram below, you can see the pinout of a typical 12V relay. Note that each pin is numbered.
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