When Hitaltech, the enclosures and connectors specialist, attends the Engineering Design Show this October, it will be bringing with it a wide range of innovations. Yet it is not only the preview of its latest enclosure (a BAC-box designed specifically for the building automation controls market, that fits over the standard UK double-gang back box), its connectors or its flat, vibration and stress resistant flexible cables that will be on display. Its experts – the people who work closely with designers – will be there too to answer questions. And one of the most frequent conversations they are likely to have will involve terminal blocks.
When it comes to selecting the right terminal block, the process can be as complex and daunting as selecting the right microprocessor. Terminal blocks come in a multitude of shapes and sizes with many manufacturers and suppliers offering thousands of variations.
Yet with such a wide range to choose from, designers can face a challenge in selecting the right terminal block for the job. In this guide Hitaltech offers the following considerations to help narrow the field:
Connection Method
Plug and socket type terminal blocks offer the benefit of quick installation and removal and help to avoid mis-wiring during installation and servicing, however there is usually a premium to pay when compared with a fixed PCB mounted terminal block.
Screw type terminal blocks are widely used and accepted in a large number of field wiring applications, and accept a wide range of stranded and solid conductors. On the other hand ‘screwless’ types are useful in high vibration applications or when high speed of wiring is desirable.
Wire Entry Size
The wire entry size is usually quoted in mm2 or AWG (American wire gauge) and is determined by amperage ratings, the type of conductor being used, i.e. solid or stranded and the range of conductor sizes that may be used during field wiring. It may also be desirable to use ferrules on the end of conductors during factory wiring processes.
Number of Poles
Terminal blocks come in a variety of single row or multi-row blocks from a single pole (1 wire entry) to multiple wire entries. High quality terminal block producers can achieve as many as 25 poles in one monolithic block whilst maintaining the required pitch tolerance. There are also modular types which can be dovetailed together into larger blocks.
Pitch
Consideration needs to be given to the required voltage ratings of the application, creepage and clearance constraints and relevant approvals criteria. The pitch of the terminal block also impacts on their physical size and often presents a challenge to design engineers when balancing size constraints against achieving the relevant approval standards.
Geometry
There are many geometric considerations when selecting a terminal block, from the desired angle of wire entry relevant to the PCB to the general appearance of the finished product. Designers beware! The humble terminal block is usually the first part of your product which is used by your customer. Therefore appearance, durability, usability and reliability are just a few of the considerations you need to make.
Assembly Process
Traditionally terminal blocks are hand placed and either hand soldered or wave soldered during the second stage of production. However with the push towards automating production processes, there are now terminal blocks made from high temperature plastics, supplied in tape on reel packaging for automatic placement and re-flow soldering.
Customisation
Finally, although there are thousands of standard types of terminal blocks available from a large number of producers and suppliers, there is still a need for a level of customisation. For a specialist supplier such as Hitaltech, understanding the needs of the designer is paramount in helping at the early stages of the design process to select the right product. Hitaltech can advise on the selection of a massive range of standard screw, screwless, plug and socket or PCB mounted terminal blocks. This advice extends to customisation options which include: custom colours, custom markings, pitch variations and geometric variations.
