Seen floating around the internet, and replicated on Wikipedia.
- There is no such thing as ground.
- Digital circuits are made from analog parts.
- Prototype designs always work.
- Asserted timing conditions are designed first; un-asserted timing conditions are found later.
- When all but one wire in a group of wires switch, that one will switch also.
- When all but one gate in a module switches, that one will switch also.
- Every little pico farad has a nano henry all its own.
- Capacitors convert voltage glitches to current glitches (conservation of energy).
- Interconnecting wires are probably transmission lines.
- Synchronizing circuits may take forever to make a decision.
- Worse-case tolerances never add - but when they do, they are found in the best customer’s machine.
- Diagnostics are highly efficient in finding solved problems.
- Processing systems are only partially tested since it is impractical to simulate all possible machine states.
- Murphy’s Laws apply 95 percent of the time. The other 5 percent of the time is a coffee break.
One I’ll add that I’ve heard before, in the context of new circuit board designers and cross sectional area of high current traces: “Copper isn’t a superconductor.”
Since several of us here play in these spaces or near them…
The worst I’ve found is actually the wiring conduit on my Ford 9N tractor. There’s a metal tube that runs from the front of the engine to the back, with openings on the side for spark plug wires.
The tube contains:
4x spark plug wires
1x generator wire, coming to charge the battery
1x ignition wire, coming forward from the ignition switch to power the points
I’ve literally never seen a digital voltmeter glitch and fail like it does trying to measure battery voltage on this tractor when running. One would expect some nasty spikes on the lines, running in parallel with the spark plug wires. One would not expect a digital meter, on the 6V battery, to glitch, reboot, blank out, and generally freak out entirely trying to measure battery voltage.
This is such a well known effect on these tractors that one of the “50 Tips” entries reads:
- A digital multi-meter is a handy and usually inexpensive tool to have around the shop. But, most inexpensive digital multi-meters do not like the electrical “noise” produced by the N’s generator brushes. The test leads act as antennas and the meter gives some erratic readings as a result. Stick with the old analog meter for your old N.
I’m not so sure it’s generator noise as induced voltages from the wire conduit. In any case, I’m curious, but not curious enough to risk a good oscilloscope trying to figure out what’s going on…