A relay is an electrically operated switch that can be used to control a circuit utilizing a low-power signal. It lets electricity be delivered to a device over the shortest possible distance to reduce voltage loss. It is widely utilized in a variety of applications, including automotive, industrial, and household systems, where it is necessary to manage a circuit utilizing a low-power signal from a switch or sensor. In industrial applications, relays may be utilized to manage motors, pumps, or other heavy-load circuits.
A relay has many types of contact configurations. The normally open relay and the (NC) relay are a state of the relay. It is the open and closed position of contacts in the relay. A car exercises different types of relays depending on the need of the work, so it is important to know the concept of the normally open and (NC) relay.
Car relay information is useful for understanding how to use and maintain these electrical components in automotive systems. In this powerful guide, you will learn the normally open relay and (NC) relay, diagrams, symbols, and how to check them.
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First Understand The Wiring Diagram Of Relay
Before starting, first, you should understand the wiring diagram of the relay. A relay has two circuits, a coil (electromagnet), and a high amperage route. Each route has two terminals. The coil route’s terminals are 85 and 86. Terminal 85 is given a negative energy source, and 86 is given a positive energy source.
The relay’s second high amperage route consists of two terminals called 30 and 87, in which terminal 30 is a common terminal. It means through terminal 30, the battery’s 12-volt energy source enters the relay. Similarly, the relay’s high amperage route’s terminal 87 is considered a power-out terminal. It means through terminal 87, the 12-volt energy leaves the relay and goes to the component.
In a five-pin relay, the relay’s high amperage circuit consists of three terminals, 30, 87, and 87a. Terminal 87a is a fifth extra terminal utilized for circuits when energy is required without energizing the relay.
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Normally Open Relay
The normally open (NO) relay means, by default, the relay’s contacts are open and do not have connections. When the relay’s high amperage route links (Terminal 30 and 87) stay separate from each other without energizing the relay in normal conditions, this kind of relay is called the Normally Open (NO) relay.
If you connect a normally open relay (open-position relays) in a circuit, it will not let the current pass. By energizing the relay, the relay’s links close, and the current starts to flow. Open-position relays are utilized everywhere in the car, like air conditioners, fog lights, horns, fans, etc.
For example, if an open position relay is operated to manage a car’s headlights, the headlights would be off by default. When the relay is activated, the links would close and the headlights would turn on. When the relay is de-energized, the links would open and the headlights would turn off.
Normally Open Relay Symbol
This is the symbol of the open position relay. It is utilized for representing the links of the relay that are open when there is no energy supplied. It means the link is open (break) & there is no flow of current by default and gets closed and starts the current flow when activated.
This is an Info
The open and closed position of a relay depends upon the design and need for work in a car.
This is an Info
By default, some four-pin relays are Normally Open (NO), and some are Normally Closed (NC).
Normally Open Relay Diagram
In the above picture, you can see a 12v 4 pin normally open relay diagram, in which the relay’s high amperage route’s links are open and do not have a connection. By energizing the relay, the relay’s high amperage route’s links will change from an open to a closed state and create a path for the current to flow.
How Do You Tell if a Relay is NO (Normally Open)
- Identify the relay’s high amperage connection.
- Take the multimeter and put it in ohm or continuity mode.
- Touch the multimeter ohm or continuity leads with the relay’s high amperage route
- If you get some reading in ohmmeter, it means your links are bad. If you get an Open Load (OL) reading in the ohmmeter, it means your open position links are in good condition.
- If you do not get a beep sound in continuity mode, it means the links are good, but if get a beep sound it means the links are bad.
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Normally Closed Relay
The (NC) relay is the opposite of the normally open relay in function. When the relay’s high amperage route’s links(Terminal 30 and 87) are closed (Touch) each other without energizing the relay in normal conditions, called Normally-Closed (NC). The (NC) relay’s links are closed by default and have a connection. It will remain in the closed position until the relay is energized.
For example, the headlights of a car may be managed by an NC (Normally-Closed) relay that is activated when the ignition switch is turned off. When the ignition switch is turned off, the relay is energized, and the links open, causing the headlights to turn off. This ensures that the headlights are not left on accidentally, which could drain the car’s battery.
Normally Closed Relay Symbol
This is the symbol of the NC relay. The (NC) relay’s links are in the closed position when there is no power supplied. The relay’s links open when the relay activates to break the connection.
Normally Closed Relay Diagram
In the above, (NC) relay diagram, the relay’s high amperage route links are by default closed, and the current is flowing even if the relay is not energized. These relay links will open when the relay is energized, and the current will stop flowing.
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How Do You Tell if a Relay is NC (Normally Closed)
- Identify the relay’s high amperage connection.
- Take the multimeter and put it in ohm or continuity mode.
- Touch the multimeter ohm or continuity leads with the relay’s high amperage route.
- If you get some reading in ohmmeter, it means your links are ok. If you get an Open Load (OL) reading in ohmmeter, it means your open position links are bad.
- If you do not get a beep sound in continuity mode, it means the contacts are bad, but if get a beep sound it means the links are good
Note:
The current rating of a car relay determines the amount of current that it can safely handle without overheating or malfunctioning. They are used in a variety of automotive appliances to protect circuits and manage heavy-load devices such as motors and pumps. They are available in a variety of shapes and sizes to suit the needs, thereby, it is important to choose the right one from a reputable manufacturer to ensure that it functions well and protects the circuits it controls.
As you can see, learning normally open and closed relay is no more a mystery, anyone can learn in a few minutes.
5 pin relays have the link points at the same time, Normally Open (NO) and Normally-Closed (NC). This extra 87a terminal gives the five-pin relay both features at the same time.
What Is The Difference Between Normally Open And Normally Closed Relay
There are two main kinds of relays: normally open (NO) and normally closed (NC). The difference between these two kinds of relays lies in their default positions when no current is applied to the coil.
- A normally open relay has a set of links that are normally open or disconnected when the coil of the relay is de-energized (is not yet energized or in its relaxed state). When current is applied to the coil, it becomes magnetized and the movable links are attracted to the fixed link, closing the circuit and allowing current to flow through the links. This kind of relay is often applied to start or stop a circuit when a certain condition is met, such as when a button is pressed or a sensor is triggered.
- A normally-closed relay, on the other hand, has a set of links that are normally-closed, or connected, when the coil is de-energized (is not yet energized or in its relaxed state). When current is applied to the coil, it becomes magnetized and the movable link is attracted away from the fixed link, opening the circuit and interrupting the flow of current through the links. This kind of relay is often applied as a safety feature to automatically cut off power in the event of a malfunction or other emergency.
It’s important to note that both normally open and normally closed contacts can be utilized to start or stop a connection, depending on how they are corded and the specific requirements of the products. For example, a normally open relay could be utilized to start a connection by closing the links when a button is pressed, while an NC relay could be utilized to stop a connection by opening the links when a sensor is triggered.
Conclusion
In summary, the main gap between normally open and normally-closed relays is the default physical position of the links when the coil is de-energized. A normally open relay has open links, while a normally-closed relay has closed links. Both kinds of relays can be operated to start or stop a circuit, depending on how they are corded and the specific requirements of the appliance.
Frequently Asked Questions (FAQs)
The function of a normally open (NO) relay is to interrupt the flow of current through a connection by default and allow the current to flow through the connection when the relay is activated.
The function of a normally closed (NC) relay is to allow the flow of current through a connection by default and interrupt the flow of current when the relay is activated.
A (NC) relay works by allowing the flow of current through a connection by default and interrupting the flow of current when the relay is activated by a low-power signal such as a switch or sensor.
A normally open relay works by interrupting the flow of current through a connection by default, and allowing the flow of current when the relay is activated by a low-power signal such as a switch or sensor.
The part of the relay that causes the most trouble is typically the link point. This is because, over time, the link point can become corroded or damaged, which can cause problems with the electrical current flowing through the relay. In some cases, simply cleaning the link point can solve the problem. However, if the damage is more severe, it may be necessary to replace the entire relay.
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