Problems designers can face and how we help resolve them…
The selection of the humble ‘Terminal Block’ is often overlooked by design engineers until the later stages of the design process. However, 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. The following is a summary of some of the issues faced by designers when selecting the right terminal block to do the job.
Plug and Socket type terminal blocks offer the benefit of quick installation and removal and help to avoid miss-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 high 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.
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.
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.
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 process there are now terminal blocks made from high temperature plastics and supplied in tape on reel packaging for automatic placement and re-flow soldering.
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 are able to 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.