Electromechanical relay isolate and control current flow between circuits. They have a coil, armature, and contact. An electric current through the coil creates a magnetic field that attracts the armature, moving it and making or breaking electrical connections. Due to its reliability, simplicity, and high current and voltage handling, these relays are widely utilized. Electromechanical relays’ purpose, history, working principle, kinds, and applications in power distribution systems, industrial automation, and automotive electronics will be covered in this document.
The purpose of electromechanical relays
Electromechanical relays reliably control electrical current between circuits. Based on the input signal, they switch current. Low voltage control systems are often interfaced with high voltage power systems using these relays to isolate delicate control components from greater voltages and currents. They are also utilized for amplification, signal conditioning, timing, and interlock. This section explores electromechanical relay operations and benefits.
1.2 Electromechanical Relay History
Electromechanical relays have a rich history reaching back to the early 19th century. Telegraphs were vital to relays’ development. Joseph Henry invented the first workable electromagnetic relay for telegraphy in 1835. Over time, magnetic technology and relay downsizing led to their extensive use in numerous industries. Electromechanical relays remained popular in applications demanding higher power handling or better environmental resistance despite the arrival of solid-state relays. Understanding electromechanical relay history helps explain their evolution and why they are still used today.
You’re reading this to learn electromechanical relay basics. We’ll explain these ingenious technologies’ inner workings and uses in 100 words or fewer. You’ll learn how relays turn electricity on and off and how to use them in your projects. You’ll be able to choose and set the proper electromechanical relay for each task by understanding their purpose, history, operating principles, types, and use cases. Let’s begin!
A Brief History of Electromechanical Relays
Late 1800s relays began
Before electric illumination and motors, the telegraph business needed a mechanism to repeat weak messages in long-distance cable lines. The first relays were invented in the mid-1800s utilizing electromagnets and mechanical contacts. The original telegraph relays had one contact and could switch a few hundred volts.
Early 1900s telephone exchanges
In manual telephone exchanges, larger multi-contact relays routed calls between lines after the telephone was invented. This increased relay use as electrically controlled mechanical switches to manage larger voltages and currents in diverse applications.
Multiple Industry Proliferation (1920s-1960s)
Relays were used in electric utility grids, industrial controls, computers, and test equipment in the early 20th century for control, switching, and protection. Improved designs, precision production, and testing grew the relay industry. Relays allowed telecom and aerospace automation and remote electrical switching without knobs and switches.
Transition to Solid State (1970s+)
Since the 1970s, smaller, more reliable, and faster solid state analog and digital electronics like transistors have replaced many electromagnetic relays. Simple, durable, and electrically isolated, they are excellent for many applications.
Electromechanical Relays Work How?
Electromechanical relays control switches with electromagnets. The main parts are:A low-power signal energizes an electromagnet coil, creating a magnetic field. This pulls the armature down, activating the mechanical switch.Contact Mechanism—Armature action pushes or pulls switch contacts to modify incoming and outgoing circuit connections.
The coil winding connects to a low-power circuit. Electricity flowing across the coil energizes the electromagnet, activating the switching mechanism to connect or disconnect.A small control signal to the coil magnetically operates the bigger power circuit through the relay. By converting electrical input to mechanical movement, the electromechanical relay switches on/off. By using an electromagnet and contact mechanism, these basic devices can control higher power circuits with a low voltage signal into the coil. This makes them handy for many automation and control applications.
Electromechanical Relay Types
Beginners should learn about numerous electromechanical relay kinds. This includes:
Single-Pole Single-Throw Relay
This relay is the simplest. The input controls one set of contacts that open or close. The relay coil activates the SPST, closing the circuit. Consider an SPST an on-off light switch. Useful for basic control.
Single-Pole Double-Throw Relay
SPDT relays flip between two output circuits like toggle switches with one input. The coil flips the relay to connect the normally closed or open contact. For signal routing or mode switching.
DPDT controls two outputs with two inputs and two SPDT relays. It switches connections between two circuits simultaneously.
It takes no electricity to keep this relay turned. They “latch” after activation by toggling. This makes them basic memory storage devices that stay place until triggered.
These are the most common electromechanical relays. From simple SPST on-off to complicated DPDT dual circuit switching, switches are everything. Understand these important types to improve your relay skills!
Uses for Electromechanical Relays
Control power distribution and switch circuits
Overload protection – Isolating faults or tripped circuits
Factory Automation and Industrial Equipment
Features include motor or process control, safety interlocks, machine sequencing, and alarm/shutdown systems.
- Automotive and Transport
- Controlling lights, HVAC, and wipers
- Fuel delivery regulation
- Locking doors, power windows
- Integration with engine sensors
Electronics for consumers
Switching higher voltage or current loads
Electrical isolation and time delay/timing functions implementation.