What Is PCB Relay?

Safety should always come first while working with a system that uses high voltage or current. High power systems pose too many risks to relying on component reliability arbitrarily. Designers can safeguard themselves and their devices from high-voltage discharge using various methods.

Relays are one of the standard components found in high-voltage systems. Various sizes are available for these switches, including a PCB board relay that may be mounted on a circuit board. These parts provide the safeguards high voltage systems require to operate safely and withstand power surges.

In electronics, relays are essential switching and protection components. Small relays must be welded into circuit boards as electronic devices get smaller and smaller. They are referred to as PCB relays. Here is a detailed look at how to put this device into your relay circuit board if your electronics project demands it. Let’s look at it!

What is a PCB Relay?

Relays are devices for power management that use a secondary low-power circuit to control a high-voltage circuit. A PCB relay is connected to a printed circuit board and is sometimes referred to as a print relay or a printed circuit board relay. A smaller relay that may be mounted directly on a PCB is called a PCB relay.

Due to their size and weight, these relays can be mounted as through-hole components on a printed circuit board. A relay is used every time a high-voltage circuit needs to be controlled by a second low-power circuit. Galvanic isolation, which is not possible with switching based on the transistor, is a further advantage of a relay.

How PCB Relays Function

Despite being more compact and having lower voltage ratings, PCB relays work exactly like conventional relays. These components are also available in any of the typical designs that you would see in bigger relays. These consist of the following:

• High-voltage: These are built to operate at extremely high voltages and currents.
• Overcurrent: This kind of relay opens to prevent heavy currents from moving around a circuit in the wrong direction.
• Semiconductor: Electronic switches are used in these solid-state relays.
• Time-delay: These relays only activate for a short duration.
• Thermal: Once the temperature reaches a certain point, these relays will trip.
• Differential protection: This kind of PCB relay can activate when the voltages or currents in two separate circuit components differ.
• Protecting frequencies: When an AC current has an excessively high or low frequency, these solid-state relays trip.

Each relay type has specific applications; however, they are typically found in high-voltage PCBs and high-current circuits.

What Are the Different Types of Relays Used in PCB Assembly?

The classification of a PCB relay relies on its composition, placement, use, and contacts. We can categorize relays using the following criteria using these parameters.

• Electromagnetic Relays

When activated, electromagnetic relays’ combined electrical and mechanical parts move mechanical contact sets. The electromagnet, which generates a magnetic field to open or close the contact sets, is the main component of this system. In this relay, you can use either AC or DC, and the most frequent forms are induction and attraction.

• Solid State Relays

A solid-state relay is switched in using semiconductor components rather than mechanical ones. Additionally, this device offers a larger power gain compared to the electromagnetic PCB relay. They have a lower energy control than their high power output, which accounts for their high gain.

The switching capabilities of a solid-state relay are faster than those of a typical PCB power relay. Due to the lack of contacts, it also runs silently and has a long lifespan. For instance, there are photo-coupled relays and transformer-coupled relays.

• Hybrid Relays

These relays combine electronic and electromagnetic elements that operate simultaneously but in concert. Rectification is handled by the electrical portion of the relay, while the electromagnetic portion handles the output section. This configuration has lower energy loss than solid-state relays, which leads to less power usage overall. 

• Thermal Relays

Thermal relays carry out switching operations by responding to temperature variations and adjusting the contact positions. These relays prevent equipment from overheating since temperature changes trigger the switching. These consist of temperature sensors and bimetallic components like motors.

What is the PCB Relay’s Operating Principle?

Relay PVC or plastic cases must be taken off with a screwdriver if you wish to create a PCB relay. You’ll be able to see the relay’s components. A PCB board relay circuit needs the ideal relay and a seamless installation procedure to ensure effective operation.

As a result, you must mechanically connect the armature to one or more moving contacts and hinge it on the yoke. When the relay is de-energized, the spring that is used to hold it tightly opens up, allowing air to enter the magnetic circuit. As a result, one or more sets of contacts inside the relay close while the other opens.

Depending on their utility, various relays may have fewer or additional contact sets. Additionally, it has a wire connection that runs through the yoke and connects the armature and moving contacts on the PCB, maintaining circuit continuity. The printed circuit board is where the relay is soldered.

The relay’s armature is activated when a static contact is broken or connected. In the event that the relay de-energizes while the contacts are closed, this action opens the contacts instead, causing the connection to fail. When the circumstances are reversed, the opposite occurs.

What are the PCB Relay Design Requirements?

Because people want smaller devices, smaller electromagnetic relays that can be soldered directly onto a PCB have been made. Even if smaller relays are available, the physical mounting of a circuit board relay still necessitates care with soldering, heating, and cleaning. An electromagnetic relay won’t function properly if its internal mechanism becomes deformed.

Relay mounting is advised to be done with PCBs that are 1.6 millimeters thick and made of glass-epoxy or paper-epoxy. Standard conductor thicknesses of 35 mm and 70 mm are needed for PCB relays. When subjected to magnetic fields and heat, thermal and electromagnetic relays behave in distinct ways.

Relays should be placed far from transformers, semiconductors, and other heat-generating components when designing your PCB. A product’s mechanical design must also safeguard relays from stress and vibration. Install the relay such that any shock or vibration is applied at right angles to the armature’s operating direction.

Mounting Methods for PCB Relays

The PCB’s holes and spacing should match those specified in the Finder data sheet to prevent tension from being imparted to the pins during insertion. The relay pins should NOT be bent to fasten the relay to the PCB. The interior components will receive the bending loads, which will reduce reliability.

Power and industrial relays with PCB mounts benefit greatly from the usage of plated through-hole PCBs since they provide the strongest mechanical solder bond. An aligned coil and contact points are components of a PCB relay‘s energizing circuit.

This circuit generates an electromagnetic field that acts through the metal plate attached to the armature when current passes through it. The switching effect is caused by the magnetic field’s ability to close or open the contacts. The relay contacts can then be managed in a variety of ways by using the pole count, throw count, or break the count. 

In Conclusion

Circuit boards need PCB relays as important safety equipment. Despite their compact size, they perform standard functions. When putting them into a relay circuit board, they must be handled carefully. To guarantee the relay performs as intended, consider the PCB design specifications mentioned above as well.