Lesson 4/Learning Event 1
It is good practice to provide one or more spare contacts in the connector pair, more than the
actual number required for the circuits to carry. Then, any increase in circuits necessitated by
functions added later will not require the use of another connector. It is advisable to keep the
number of contacts per connector down to a number that can be mated and separated without
excessive force. Where a large number of circuits must be handled, it may be advisable to use
more than one connector pair. Every effort should be made to choose connectors that will allow
signal and power leads to be bundled separately.
The current to be passed through each contact must be determined. The contact size then can be
established with a safety factor sufficient to provide safe operation under conditions of temporary
overload. Another important safety factor is mechanical strength. In many applications, size 12
contacts are used, even though the current may be less than 100 mA because the mechanical
strength of the size 12 contact is needed.
Great care should be exercised in the selection of connectors to make certain that they will meet
mechanical strains placed upon them in application. On vehicles, connector housings are used as
personnel steps if they happen to be in the right location, and it is not an uncommon sight to see
military equipment lifted or carried by one or more of its connectors even though connectors or
thin housings are not intended for these purposes.
The selected connector must have the means to prevent incorrect mating built into it. This may be
effected through dissimilar-size guide pins, a nonsymmetrical arrangement of contact barriers, or
the design of the connector shell housing. Contact pins should never be used for alignment or
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