Except tantalums!
I expect it was to mimic the outside foil mark on dog bone caps. Black mark goes to ground (usually).
I don't think I've ever owned a Japanese multimeter. I just have American and Chinese ones.
Life would be simpler if the early electrical guys had guessed the right sign convention for current. That and QWERTY are the only ones that come to mind right at the moment, at least in my lab.
Cheers
Phil Hobbs
IC pin numbers should count clockwise, and the footprints should always be asymmetric.
AFAIK, they *all* do, when viewed from the bottom ;-)
(Where that convention originated I have no idea.)
That would be good. But most packages today have physical shapes which ease the use of pick-and-place. ...Jim Thompson
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Another legacy - this one from when through-hole parts dominated. Tube and transistor pins were meant to be identified, laid out on PCB designs and soldered from the bottom. Through-hole ICs followed, and the pin numbers on all those devices do run clockwise from the bottom.
That would be very welcome indeed.
Probably from tubes, which were sensibly CW from below.
They could still be asymmetric. Leave out one pin, change pitches, offset one row or something.
One of my first failures while tinkering as a lad (~ age 15)... I miswired an oscillator coil (CW instead of CCW) for an AM radio and could never figure out why it didn't work. Tossed it in the garbage. After garbage collection day it dawned :-( ...Jim Thompson
Mechanical engineers love symmetry. It allows many different ways to assemble things, one of which is right.
I know absolutely nothing about PnP, but isn't that accounted for part-by-part in the programming? ...Jim Thompson
sure, the pnp does what you tell it to do, it is just easier to catch mista kes if the part won't fit on the footprint if it is the wrong way around.
one place we get stuff made the machine verifies component values and direc tions electrically
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alue.
erwise
ram saying that's what it means, but it would be likely to mislead and resu lt in screwups, so not good practice.
and connectors should be numbered odd/even on each side so that when you need change the number of circuits you just add or remove instead of having to renumber half the pins
My wife bought me a padlock with an unusual key for my lab. The tip of the key looks like a Phillips screwdriver with the four grooves extended to about an inch, with serrations along each wing. It can be inserted into the lock in four different ways but only one of them allows the key to be turned.
The serrations look similar enough to make it difficult to see which side is which except by careful examination in good light. That often makes inserting the key the correct way a matter of trial and error.
Some parts are just pulled off a reel, where the orientation is known. Tray parts, randomly oriented, are snooped by a camera that checks for correct part and determines orientation. It's very versatile, but has to be programmed. We use the semi-auto machines for short runs and first articles, because setup is easier and people check the parts as they are placed.
Our optical inspection machine rechecks the boards after they are soldered.
So are ICs if you wire them dead-bug. ;)
Cheers
Phil Hobbs
That's a cross or cruciform lock. With the right tools, it's fairly easy to rake or pick: (9:38) (5:23) (5:44) I have not tried one of these locks, yet.
Grin Yup. I like to assume all caps are uF, and so would use 0.1 Also nF is confusing to our production people, most caps are labeled as uF or pF.
George H.
Yes but they have to be taken out of the tape the right direction. I have a CM who insists on installing Seiko SOT89s backwards. I haven't looked at the latest set of boards. I hope he's figured out what he's doing wrong.
Maybe they would have got current right if they had put North at the bottom of the map, where it belongs.
Clifford Heath, Up-over.
They did. The earths magnetic north pole is actually the equivalent of the south pole of a bar magnet. So, when you point north, you're actually pointing to the magnetic south.
Drivel: Can we bring back micromicroFarads as a replacement for picoFarads? It won't do anything useful except confuse anyone trying to steal or clone the device, but that's sufficient.
More: "List of obsolete units of measurement" Perhaps we can resurrect the Fresnel as a unit frequency?
I just had a peek at my old copy of RHD and got reminded that they never used k. Resistors were in ? up to five digits and in M? above that. So 47k was written as 47,000? (with a comma) and
220k as .22M? (no leading zero).
A lot of early US potentiometers were marked with M instead of K. Have you ever used a 500,000,000 ohm resistor for a volume control? M was used for 1000 in some other industries, in the past.
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