Relays

FAQ Relay

Question: What is a relay and what is the function?

Answer: A relay is an electrically controlled switch used to control the direction of electric current. Relays are widely used in automation systems to control the operation of various devices such as motors, lights, and valves. The working principle of a relay is that in the initial state, the electrical path between the common terminal (COM) and the normally closed terminal (NC) are connected. After the relay receives an electrical signal at the control pin, the electrical path changes to connect between the common terminal (COM) and the normally open (NO) terminal instead. Relays can be used to create circuits that control the timing of operations by using a timer or programmable logic controller (PLC) to switch the relay on or off at specific times, providing a reliable and cost-effective method for controlling the timing of operations in a variety of applications.

Question: What are the types of relays?

Answer: There are various types of relays, and they are classified into different categories according to their properties.
Based On Operation Principles (4 types)
1.1 Electrothermal Relay, an electrothermal relay is made up of a bimetallic (made up of two metals having different thermal expansion coefficients) strip.
1.2 Electromechanical relays This type of relay uses electrical power to move the electromagnetic coil. to control the movement of the contact.
1.3 Solid State Relay, SSR relay is made up of semiconductors instead of mechanical parts and it works on isolating the low voltage circuit from the high voltage circuit using an optocoupler.
1.4 Hybrid Relay, Hybrid relays are made using both SSR and EMR relays. As we know that the SSR wastes power in form of heat and EMR has a contact arcing problem. The hybrid relay uses both SSR and EMR to overcome their disadvantages.
Based on Poles and Throw (4 types)
2.1 SPST (single pole single throw) relay
The single pole means that it can control only one circuit while the single throw means its pole has only one position in which it can conduct.
2.2 SPDT (single pole double throw) relay
The single pole means it can control only one circuit at a time. The double throw means its pole has two positions in which it can conduct.
2.3 DPST (double pole single throw) relay
The double pole means it can control two completely isolated individual circuits. The single throw means that each pole has one position in which it can conduct.
2.4 DPDT (double pole double throw) relay
The double pole means it can control two circuits while the double throw means each pole can conduct in two separate positions.

Question: What is the difference between 12v 24v 220v of relays?

Answer: They are the different types of voltage used to control relays.
12V and 24V relays are typically controlled by DC (Direct current) system, which is typically applied to the low-power electronic device. On the other hand, 220V relays is controlled by AC (alternating current) system, which is commonly applied to high-power consumption devices such as home appliance and industrial electrical systems.

Question: What are sockets relay used for?

Answer: Socket relays are a housing part of relays, which provides easy connection to the relay terminals (through screw or screwless terminals), and arrangement for jumper connection for easy wiring between neighboring devices.
Sockets relays can protect relays from damage while soldering to the printed circuit board (PCB) and enhance the replaceability of relays. Users can replace it by pulling the relay from the socket and inserting new relays into the sockets.

Question: What is Solid State Relay(SSR) and what is the function?

Answer: A Solid-State Relay (SSR) is a relay that does not have a moving contact. So, A Solid-State Relay (SSR) have long lifetime and able to use higher frequency operation. In terms of operation, SSRs are not very different from mechanical relays that have moving contacts. SSRs, however, employ semiconductor switching elements, such as thyristors, triacs, diodes, and transistors.

Question: What is Terminal Relays and what is the function?

Answer: Terminal Relays are defined as control and automation relay that has the form and fit of a terminal block and DIN Rail mounted to save panel space.
Terminal relay is typically used as interfacing equipment between a controller (Ex. PLC) and a high-power load (Ex. Motor).
The reason is some systems a controller cannot supply the load directly (due to different voltage requirements and insufficient driving current).