Understanding the purpose of relays in a car is critical, as the small portable component saves the lives of many bigger electrical appliances in our vehicles.
The air conditioner and taillights are just two examples of the many electrical systems in your car. When something goes wrong, it can be challenging to pinpoint the issue with one of those parts, but when it comes to the electronics of a car, there’s a good probability it’s connected to a relay.
After publishing an in-depth post about relays for general purposes, I realised that writing about automobile types would be helpful. In this article, we’ll explore what a car relay is, its applications, parts, diagram, types, and how it works. We’ll also look at its advantages and disadvantages.
Let’s Begin!
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What are Car Relays?
An electronic or electromechanical controlled switch, known as a car relay, regulates DC voltages in passenger comfort and retention systems. It also controls power levels in harsh environments. Relays, like other switches, operate through electrical power, a computer, or a control module.
The purpose of an automotive relay is to automate the power to switch electrical circuits on and off at specific times.
However, the functions of a relay are more than just automation; it provides the ability to switch multiple circuits, including different voltage types. This will happen within the same relay at the same time.
Generally, relays are electric switches that work with electromagnetism to convert small electrical stimuli to larger currents. This conversion takes place when an electrical input activates electromagnets to form or break existing circuits.
Leveraging weak inputs to power stronger current, relays can effectively act as a switch or an amplifier for the electric current. These depend on the desired applications.
Applications
The usage of relays is common in cars, as well as in maritime and aviation applications. Typically, low amperage circuits employ them to enable control over larger amperage circuits. Relays serve as switches that enable the low-amperage circuit to turn on or off the high-amperage circuit.
Car relays power specific components in various parts of vehicles. One or more appliances in a car can depend on a relay system so that they can work accordingly and stop when one of them develops a fault.
Parts in vehicles that use relays include dashboard indicator lights, headlights, braking, and trafficator lights. The engine fan also works with a relay. Windscreen, wiper, etc. in fact, along with a fuse, almost all vehicle electrical systems have a relay for their safety.
Car relays support modern electrical conveniences and safety features in vehicles by providing switching functions. These relays provide support to all types of vehicles – cars, trucks, vans, trailers, boats, etc.
12V DC relay switches are suitable for full voltage application, as a low current flow circuit can control a high current flow circuit such as a vehicle’s horn, headlights, auxiliary lamps, fan motors, blower motors, etc.
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Components of Car Relays
All relays have the same primary components, but some types may contain additional parts depending on their features in applications. The following major components are common to all types of relays:
- Frame – a container or heavy-duty frame that contains and supports the various parts of the relay.
- Coil – is a wire wound around a metal core. It’s the part that causes an electromagnetic field
- Armature – is a moving part that opens and closes the contacts. The armature can be moved back to its starting position using the spring that is attached.
- Contacts – it’s the conducting part that causes the relay to make (close) or break (open) a circuit.
Relays have two circuits: an energy circuit and a contact circuit. The energising side has the coil, while the relay contacts have the contact side. A relay coil is energised when the current flows through the coil and creates a magnetic field.
In an AC unit, the polarity changes 120 times per second; polarity is also fixed in a DC system.
Diagram
Types of Relays Use in Cars
There are many types of automotive relays used on vehicles to meet the requirements of various applications. Below are the various types of automotive relays and their functions:
Normally open relays:
Normally, open relays only have four pins and can be wired only one way; they are normally open. This is unlike the changeover types of relays that can be wired into different forms, including N.O.
Changeover relays:
These are common types of relays in vehicles; they have five standard pins. They can be wired to be Normally Open (N.O.) using pins 30 & 87 and Normally Closed (N.C.) using pins 30 & 87a.
You can also wire these relays as changeovers (both N.O. & N.C.) by using pin 30 and both pins 87 & 87a. When you use the relay as a changeover, it transfers current from one circuit to another and vice versa. This depends on the state of its coil (ON or OFF).
Dual open contact relays:
A dual open contact relay has five pins like a changeover relay but has a dual set of contacts instead of a single contact. Because of this, pins 87 & 87a are Normally Open (N.O.) inside the relay rather than 87a, which is Normally Closed (N.C.).
Potted relays:
A potted relay is a special relay that functions like other types of relays. Epoxy seals its bottom part, setting it apart from other relay types and preventing water penetration. The limitation of the potted relay is that it cannot be repaired.
LED flashers:
Led types of flashers are electrically controlled by a small solid-state integrated circuit (I.C.) board. The design allows it to function seamlessly with the low current draw of LED lighting. Well, several connected lights do not affect its output.
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Time delay relays:
Time relays, a popular type of relay, are adjustable to maintain and control current flow through their contacts. Duration of the current flow can also be adjusted from as little as 2 seconds to as long as 3 minutes 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 exited so that you are around the vehicle.
Flasher relay:
A 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.
To inform the user when the flasher is on, connect a three-pin flasher with an additional pin to an indicator light. Not all flasher’s relays operate as a relay; some act more like circuit breakers. However, we still classify them as relays.
Thermal (standard) flasher:
Similar to a circuit breaker, most flasher relays operate through thermal control. Current flows through the coil of the flasher relay to create enough heat. This heat causes the contacts inside the relay to deflect and open, stopping the current flow.
After dispelling enough heat, the contacts will return to their original position, allowing a new current to flow. The constant “making and breaking” of these contacts results in a flash pattern of turn signals.
Well, the number of lights connected to a thermal flasher will determine its output performance.
Electromechanical flasher:
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 number of lights connected to these types of flashers has less effect on its output.
Wig-wag flashers:
Wig-wag types of flashers are also known as alternating flashers that use a solid-state flash circuit. This circuit helps to alternate between two separate lamp circuits.
Skirted relays:
Skirted types of relays have an extended skirt around their bottom to seal around a socket. This arrangement prevents water and contaminants from entering the relay contacts. Automobiles often use these relays in exposed areas.
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How does a relay work in a car?
The working of relays is less complex and can be easily understood. If a relay is open, you’ll see an electromagnet coil, a switch, and a spring in it. This spring holds the switch in position until a current passes through the coil.
The coil then generates a magnetic field that moves the switch that turns on and off.
In the above diagram, there is a pinout of a typical 12V relay. We have numbered these pins; the coil pins are 85 and 86, and the switch pins are 30, 87, and 87a. 87 and 87a pins are the two contacts that 30 will connect.
If the coil is off, 30 is always connected to 87a. However, when the coil receives current, 30 will make contact with pin 87.
Well, depending on how you want a relay to work, you can set 87 and 87a to be either open or closed. If your equipment requires a closed relay, you will want to wire it to 87a; it can also be reversed if you want a normal open relay.
Most relays have labels at the bottom to make identifying the power source easy.
As an illustration, consider the headlights of your car. The amperage could surpass the switch’s capacity if you attached the lights directly to it, which could lead to cables melting and possibly even a fire in some circumstances.
Relays can also manage many systems simultaneously, such as turning on the headlights in conjunction with the radio or extending the antenna in conjunction with the windscreen wipers.
Advantages
Below are the benefits of relays in all kinds of cars:
- The process involves switching a high-current circuit using a low-current circuit.
- Multiple circuits can be activated using a single switch.
- Execution of logic functions.
- It saves money due to its low cost.
- Automotive relays can switch AC and DC. Transistors can only switch DC.
Disadvantages:
- Relays are too big for switching small currents.
- They cannot switch rapidly compared to transistors, except for reed relays.
- The current flowing through the coil uses more power.
- A transistor may be required to switch the current for the relay’s coil.