Facebook
Google
GitHub
LinkedinPCBs
Questions relating to project management
8 questions By Tony R. Kuphaldt
-
Question 7 of 8
Reveal answerCheck with your instructor to see whether or not your design looks viable.
Notes:The purpose of this form is to get students thinking in more concrete terms about what they intend to build. Too often, students begin assembling a prototype without a clear idea of what their circuit should look like. Once students have documented their rough ideas, the instructor may provide more targeted help to each student or team of students before they begin assembly.
-
Question 8 of 8
Identify the problem(s) with the following project construction and wiring practices, explaining how these practices could be improved upon, and why:
Wires cut as short as possible, stretched point-to-point:
Compression lugs crimped over solid wire:
Compression lugs crimped using ordinary pliers:
Bare wire ends clamped beneath nuts (or nuts and washers) on threaded studs:
Solid wires used in places where bending regularly occurs:
Signal and power wires bundled together:
Components anchored in place by glue rather than by removable fasteners:
Reveal answerWires cut as short as possible, stretched point-to-point:
When wires are strung in such a point-to-point fashion, several problems arise. First, they are more easily pulled loose from their connection points. Second, they tend to impede access to other components by occupying open space inside the enclosure rather than “hugging” flat surfaces. Third, short wire lengths place more stress on the wires and the connections when vibration occurs.
Compression lugs crimped over solid wire:
Solid, electrical-grade copper does not have enough elasticity to maintain proper tension against the barrel of a small compression-style lug. Over time, a solid wire will work itself loose from a such a lug. Stranded wire is the proper type of wire to use in this application.
Compression lugs crimped using ordinary pliers:
Special crimping pliers are designed to compress the barrel of the lug unevenly, so that the wire is securely held between ridges formed under the pressure of crimping. Regular pliers with their flat jaws are unable to produce these ridges in the barrel, leaving the wire much less secure.
Bare wire ends clamped beneath nuts (or nuts and washers) on threaded studs:
When any tension is placed on the wire, it will try to turn the nut. This is why lugs should always be crimped on to the end of a wire to attach that wire to a stud: the lug will not exert a torque on the holding nut.
Solid wires used in places where bending occurs:
Copper will harden if repeatedly stressed, leading to brittleness and fatigue. Solid wire does not bend easily, and will eventually break where it is forced to bend. Stranded wire is much more supple, and takes bending much better than solid wire.
Signal and power wires bundled together:
Close proximity between wires leads to inductive and capacitive coupling. When power and signal wires are placed together, the larger currents and voltages in the power conductors will likely couple unwanted noise into the signal wiring. As a rule, always separate power and signal wiring. If these wires must cross paths, do so at right angles to minimize coupling.
Components anchored in place by glue rather than by removable fasteners:
Glued components are much more difficult to replace than fastened components. Always build your projects with future maintenance in mind!
Notes:The purpose of this question is to introduce students to good wiring practices. By asking them to identify what is wrong with a set of improper practices, they are more likely to pay attention than if you simply tell them the right way to do things.
