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by noduerme
1238 days ago
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>> Now build a robot that measures AC for you and you have an API for your analog computer. This line made me laugh out loud, but what an amazing explanation and set of examples. Thank you. The original ECU in my 1980 Datsun ... is digital, right? I just never thought of the insane analog vacuum pot system that controls the cold start valve and the air conditioning selector and the cruise control to also be a "computer" but I guess it does compute things, in its humble way ;) |
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Does a 1980's Datsun have an ECU? That's not obvious to me. Even a 6502 would be an expensive add on at the time given car margins. Maybe a one bit controller?
But there are analog solutions to all these control situations. And you don't need vacuum tubes!
Measuring and adjusting the fuel-air mix is the carburetor's job. The carb doesnt just add fuel. It adds the right amount of fuel. Its needle calibrates it for different conditions (namely pressure).
The spark advance "computer" was super cool. Originally spark advance was a lever controlled by the user. Faster rpm -> adjust for more advance. Eventually the lever was attached to a governor (a set of balls attached to a spinning linkage and a stiff spring. It measures rpm) and the spark advance disappeared under the hood.
The automatic version of your car would have had a (very complicated) hydraulic circuit in the tranny pushing pistons that measure throttle, rpm, velocity and choose the gear accordingly.
The manual version had a vast organic neural network doing the same job but using just sound pitch of the engine. The manual transmission was cheaper because it didn't include the neural network shifter except on the very highest end cars - think RRs - and then only as a service (early SAS model).
German WW2 aircraft were fuel injected so they probably used a governor attached to the throttle wire and pressure gauge to guesstimate the mass flow and therefore the fuel to inject. There's a front page HN submission - the fuel control system of those engines or the original Mercedes Gull-wing!
All of the hydro-mechanical stuff described were slowly transistorized (but kept analog) in the 70s. In the late 80s to 90s everything became digital except the transmissions that took longer.