Originally Posted by
Landroger
I haven't needed to read a diagram like that in .... a whole grown up persons lifetime!
AND gates and OR gates, 'Op Amps' and an Exclusive OR, if I'm not mistaken?
No, you're right.
In my case, it's easier... I've become bitten by the Concorde bug again over the last ten years or so, and pulled dozens of similar diagrams from the documentation to refresh my memory.
Certainly it sounds, from time to time, that there were a million little black boxes dotted all over her airframe.
I recently tried to do a rough list, but I lost count after sixty or so.....
I suspect however, that many of the 'terms' and 'laws' spoken about are simply a gate or two, perhaps an op' amp, placed in a larger circuit that modulates the output of that board, thus creating the law or term.
The gates took care of the actual logic, but all the terms and laws and similar computing was done with op-amps.
Op-amps also were used for other functions such as demodulators (converting AC signals to DC) or comparators and level detectors.
I still mean to write some posts on "how to compute without a digital computer", but it'll have to wait until after the holidays.
Digital control is a hell of a lot easier than Analogue - in my humble opinion.
I heartily disagree, Roger.
In the 'olden' days we'd draw block diagrams like the one for the SFC, and once we agreed about all the functions we wanted, we just drew the schematics for each of the functions.
No sequencing, no real-time clock, no A/D or D/A conversion, no worries about cycle time or memory allocation. No programming-language issues, no naming of variables, no compiler faults, no software to debug.
You should try it sometime......
The major issue was, of course, that you ended up with a lot more hardware for the same functionalities, hence more weight, and more power consumption.
And the other issue, already alluded to in earlier posts, is that analogue computing is inherently not highly accurate.
In many cases of system control, a percent or two of precision is perfectly acceptable. But if a far higher precision is needed, like for instance in the intertial navigation system, or the core computing for the air intakes, only digital computing can do the job.
Seasons greetings to everyone on this thread from me too.
Christian