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Miniature relays

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Miniature relays

Miniature relays are used in industrial automation systems, intermediary systems and electronic devices. They are implemented both as electromagnetic and semiconductor.

Miniature electromagnetic and semiconductor relays

Electromagnetic and semiconductor relays (SSR) differ from each other in terms of design and the way of making connections. In electromagnetic relays they are performed mechanically, while the SSR contains an optical element (e.g. an optocoupler) and switching is performed by thyristors, triacs (alternistors) and transistors.

Miniature relays keep the advantages and disadvantages of their larger counterparts. It is these features that determine the choice of an SSR or miniature electromagnetic relay in a given case. The most important advantages of semiconductor relays are: durability, mechanical resistance and resistance to pollution, speed of operation, no electromagnetic interference, no electric arc and no moving parts, as well as low power sufficient for actuation and the ability to switch large inrush currents.

In turn, electromagnetic relays are characterized by negligible voltage drops, high resistance to overvoltage and zero leakage current, therefore they are better suited to systems where these features are essential.

Coils and contacts - the most important elements of electromagnetic relays

The basic elements of the construction of electromagnetic relays are coils and contacts. In order for the relay to work, the electromagnet coil must be actuated, i.e. the voltage must be applied to it. The excitation creates a magnetic field, thanks to which the steel armature is attracted, and the contact is closed or opened - depending on its type. The relays use make contacts (Z), which do not conduct current before applying voltage and close when the coil is actuated, normally open contacts (R) conduct current and break the circuit when voltage is applied to the coil, and changeover contacts (P) - switching between two states.

Printed circuits, twilight switches, alarm systems and other automation systems with electromagnetic relays

Electromagnetic miniature relays are widely used in industrial automation systems, residential building installations and control devices. They are the basic elements of automation of alarm systems, lighting control systems or devices such as twilight switches, and even household appliances.

Miniature relays are also used for printed circuits (PCBs), which are used in the assembly of electronic components. They are present in many electronic devices such as a computer, monitor, TV or printer. They are also found in some toys, such as educational robots and programmable dolls or stuffed animals.

Miniature solid state relays

Semiconductor relays are used in automatic systems and control devices. In terms of functionality, SSRs are equivalents of electromagnetic relays and their task is to control the current load with the participation of a power semiconductor component (e.g. triac or thyristor).

Galvanic separation in SSR is realized by means of an optical coupling (optocoupler, optotriac), which separates the input circuit of the relay from the output circuit, i.e. power executive circuit. A solid-state relay provides a much wider spectrum of possibilities than an electromagnetic relay in terms of the type of load control. It allows for a fairly significant increase in the switching frequency, performs load switching off at zero current and provides the possibility to select the moment of load switching. The SSR provides the perfect interface between the low voltage control circuit and the high voltage zone of the electrical circuits. They also enable pulse switching on and off of the flow of electricity from the source to the receiver.