Rube Goldbergs in Spaaaace

Main thing with Firewire was the 6 pin version, which could be plugged in backwards by the less aware user, which them both destroyed the plug and socket, and also fried the interface both sides, because you now fed the power voltage back into the device and the computer. 4 pin was a lot better, but no longer self powering, but worked well with early DV cameras as interface, because it could stream the video off in real time.

As to ladder logic, I have worked with it both as PLC and as real physical ladder logic, and the major advantage is that you do not need to train much to use it in the field, once you have a little understanding on how the plug in interface unit works, it is easy to do minor changes to the equipment on the fly, and millions of machines come with impenetrable instruction manuals in Chinese, but the ladder logic at least has pin layouts in English, or at least English numbers, and a little help text in English as well in the controller, so you can at least work out what it is doing, and what it is doing wrong, to fix the problem.

Mostly using the editor to change output pin, because some other fault, now fixed, has fried the particular port, and getting a new one will take a 3 month wait, but you need this thing running now.

Dave mentioned DB15 and DB9 connectors, I think he meant DA15 and DE9. The second letter is the shell size code. Originally the D sub miniature connector series DA had 15, DB 25, DC 37, DD 50, and DE 9 pins. The RS 232 serial standard assumed a DB25 connector which made it big time as microcomputers took off in early 1980s . On the PC-A/T IBM used a DE9 connector to save space and that was when folk began misnaming DE9 as DB9. By using high pin density later on 23 pins were put into A shells so DA23 became possible, etc etc. The most famous example of this is the VGA DE15 connector,. Strictly speaking a DB9 is conceivable but I never met one that wasn’t really DE9. I actually have some DE3 and DE5 connectors left over from HP equipment, so putting bigger spaced pins was done. I still have never seen a DB9 connector though!

I am listening to this episode while working on Ladder Logic for an Allen-Bradley L71S PLC.