Terminals are needed to establish an electrical connection between the current-carrying components of a relay and an external circuit. There is a wide range of terminals available for this purpose, such as screw-type, threaded-stud, quick-connect, pierced or wire-solder lug, taper-tab, octal base, and other plug-in types. Additionally, terminals can also be provided for printed or dip-solder circuits. Common enclosures and terminals are depicted in Fig. below.
Relays can come with plugs and sockets available in sizes ranging from miniature electron tube sizes to octaltube varieties. However there is one possible disadvantage when using socket mounting; additional contact faces may be needed due to the standard number of positions in the socket. A few common relay sockets are illustrated in Fig.
Quick connectors can come in a variety of forms, such as flat tab or terminal with a dimple or hole and a matching spring fitting that slides over the dimple or hole to make the connection and secure both parts together.
Screw terminals are available in many sizes from small machine screws to large studs and bolts; making them an ideal solution for frequent changes or when screwdrivers or wrenches are all that are available.
Solder terminals consist of eyelets, stiff bent-wire terminals, flat, and pierced-tab connections that have a hook or hole. A connecting wire is looped around and through the terminal for mechanical strength in addition to an electrical connection.
Solderless wrap uses a power-wrapping method with a conductor wire around a rectangular or square pin with sharp edges; this process is secured tightly to ensure it won’t come undone easily. A special tool is used for wrapping the wire adequately.
Relay Mountings and Enclosures
Relay mountings often come in the form of studs, clamps, or brackets to ensure secure connections. Most manufacturers offer several different mountings for their relays and press-fit terminals are sufficient for many classes of relays.
The performance of the relay should be a priority but enclosures are more important if they will operate in adverse environmental conditions. To protect components from damage, open relays should have some kind of protective finish applied.
Enclosures can help protect relay adjustments from physical disturbances and can also prevent accidental contact with exposed electrical parts when workers are nearby.
Generally, there are two main types of enclosures; dust-tight and hermetically sealed. Dust-tight enclosures can be made of metal or plastic and sealed with gaskets or potting materials. On the other hand, hermetically sealed enclosures are usually created using metal cans but molded plastic covers may also provide adequate protection.