Best practices for generating wiring diagrams

Question

I started a new job a few months ago with a company that designs heavy machinery used in construction (excavators, backhoes, etc.).

I am finding their wiring diagrams (they call them schematics) are extremely messy, and it is hard to find what you are looking for without having to flip through each and every page.

I am looking for some best practices from someone with experience in this industry on what I should include on a wiring diagram.

Are there any good examples that someone has that I can review?

Some other questions I have:

1. Are harnesses usually shown on a wiring diagram?
2. are connectors usually shown?
3. How should the wiring diagram be laid out?

Thanks.

Answer 1

I think good practices are to

• display all components, (even connectors, unconnected pins, unused logical gates from an IC for example etc...)
• if needed, display a function as a diagram-block style if you don't know yet the solution for it
• avoid crossing wires
• put all inputs on left
• put all outputs on right
• always put positive voltage in high direction
• always put negative voltage & ground in down direction
• separate sub-diagrams by functions (power/input/compare/amplification/logic/outputs) and so on
• add enough & pertinent comments (functions/optional or not etc...)
• display values of components with their tolerance when already known

This should be the real minimum.

Answer 2

My experience is that harnesses and connectors are usually included, but not on the same page as any circuitry -- Usually on their own page.

Most often, labels are placed on each pin, and the labels are used on all the other pages.

Answer 3

It really depends on if you need the diagram to indicate where the wires go or if you need to indicate how to manufacture them for contractors or internally.

A system block diagram can indicate where the wires go from board to board or device to device ect.

A manufacturing diagram should indicate how to construct the cable. It needs to indicate part numbers for pins, connectors and shells, and clearly mark where the wires/pins go.

Some ideas:

• Generate either diagram in your favorite block diagram program (mine is visio)
• Mark pins (by number) at least mark pin 1.
• Mark what the connector is (usually with a part number for shell)
• Indicate wire size and if the wires are twisted or shielded
• Wire lengths and colors
• Wire material
• Where the wires go (like to a designator on a PCB)