Any electrical system that may be unsafe to approach while powered should have a manual kill switch installed that:
Disables all energetics or potentially unsafe components.
Can be operated without requiring the rocket to be taken off the tower (e.g. mag-switches).
Does not require any software to work.
Wiring should be done so that the circuit is as readable as possible. If supplies allow, use a different insulation color for each wire. At the very least, positive should be red, ground should be black, and all other wires should not be red or black.
If there is space, and it is likely wires could get easily mixed up, wires should be labeled.
All switches and connectors need unambiguous labeling. Labeling should be permanent (i.e. not on tape, etc).
All wires used should be rated for the current going through them.
Strain relief:
Wires that get handled, moved, or torqued at any point should be strain relieved on both sides of that point.
Wires should be relieved to the point where they can survive very violent shaking (especially if the system will be going in the rocket).
Avoid tight wires between two points.
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