Most electronics constructional projects involve at least some degree of soldering and wiring. Many projects have a printed circuit board, PCB, forming most of the project, but it is necessary to connect the PCB to other controls and sockets, etc elsewhere within the final project. The connections that are made to many of these items will be exposed. In many cases this many not be a problem, but for others it is not wise to leave the connections exposed. This is particularly true when connections carry high voltages. In cases like these, special sleeves can be used to protect these connections. Additionally sleeves can be used when wiring to small multiway connectors where exposed wires could bend slightly and short to one another. Using sleeves prevents these accidental short circuits happening.
Types of sleeves and sleeving
There are a number of ways in which exposed terminals and soldered connections can be insulated and protected from being accidentally touched. Some methods are better than others:
- Insulating tape: This solution should be avoided at all costs. Although insulating tape is freely available and can be used in emergencies, it is not recommended for a permanent solution. The tape often slips and may come loose after a while. Additionally it leaves a sticky film over any areas where it has been.
- Rubber sleeves: These rubber sleeves can be used to slip over the joint and provide a neat and effective way if protecting a soldered joint or connection from being accidentally touched.
- Heat shrink sleeving: While similar in approach to the ordinary rubber sleeving, the heat shrink variety is also effective. A size is chosen to slip over the required area. Once heated the sleeving will shrink over the joint and remain firmly in place.
All three of the methods mentioned above are widely used. However the first should not be used unless absolutely necessary and then only temporarily. The other methods using forms of sleeving are the most satisfactory.
The sleeves used in electronics construction are normally yellow or sometimes pink and they come in a variety of diameters. Although it is possible to cut long lengths to suit, typically these sleeves are bought as set lengths which are then used.
When using rubber sleeves they can be slipped on to the wire prior to soldering, and once the joint has been made, they can be moved into position over the joint. As might be expected, sometimes when the rubber sleeve is a tight fit over the soldered joint or area to be protected, they can be difficult to slide into position. To help with this problem a small drop of light mineral oil can help considerably. Care must be taken to use the minimum amount, otherwise the sleeve may easily move out of position at some later time.
For large diameter sleeves used to contain a number of wires, it is often necessary to stretch the sleeve so that new wires can be entered into the loom or cable as it is made up. Special sleeve stretching tools can be obtained for this purpose.
Heat shrink sleeving
Heat shrink sleeving is a particularly useful form of insulating sleeving. It can be bought in long lengths and in a variety of diameters. Typically, when used, the required length is cut from the main length, and this is slipped over the area that requires protection. In general the smallest diameter that can be fitted over the area to be protected should be used.
Once in place a heat gun can be used to heat the sleeving so that it shrinks over the joint. As the heat shrink sleeving will shrink over the joint and follow its contours, it will normally stay firmly in place.
Normally a special heat gun is used to shrink the sleeving, although care must be taken not to damage other areas by getting them too hot. For those without heat guns, the heat rising from a soldering iron can be used, although care should be taken not to touch the sleeving with the iron, otherwise it will burn slightly and become discoloured. Typically the heat shrink sleeving will shrink at temperatures just over 100C. Some types are specified for 105C, others for 135C, and specialised high temperature types may even be as high as 175C, although these types of heat shrink sleeves are unlikely to be used for general electronics applications.
Both heat shrink sleeving and rubber sleeves can provide good levels of protection against leaving soldered joints and other joints unprotected. Although the rubber sleeves or heat shrink sleeves may appear to be another stage to be completed in a construction job, they can enhance the professional look of the work, apart from providing additional safety, and protection against wires accidentally shorting together.