Electronics > Beginners

Where is pin #1 for NE555P

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james_s:

--- Quote from: Howardlong on May 06, 2019, 09:11:22 pm ---
--- Quote from: james_s on May 06, 2019, 08:41:19 pm ---.

And I think the above answer has an error, looking down on the top of the IC pin one is the *bottom* left, not the top.

--- End quote ---

I may be misunderstanding, are you referring to this?

“in the traditional orientation package diagram of DIP, SOIC and SSOP packages, pin 1 is always shown top left.”

Or this?

“If you turn your picture clockwise 90 degrees, the marker is at the top left, the same a standard DIP pinout diagram.”

Or something else?

--- End quote ---

Apparently my reading comprehension suffers a bit on a Monday morning.

I was thinking in terms of the IC being oriented so that the printing on it is right side up, so the dot is on the left and pin 1 is the bottom-left pin. If you rotate the IC "sideways" so the notch is at the top then pin 1 is going to be the top-left.

alsetalokin4017:
If Pin 1 is at top left, why is the printing on the IC always sideways?   :-//

Wouldn't it make more sense to have the printing horizontal as is normal, and the Pin 1 be the bottom left?    :-DD

Now, what is really confusing is when the schematic has the pins all mixed up for routing purposes and they are labeled by their functions rather than their numbers. I think that must be done as a cruel joke by designers played on beginners.      |O

Nerull:
The dot should only be trusted if there is no notch and it is specifically called out in the datasheets. You will encounter ships that have that injection moldering dot on the complete opposite end of the chip from the pin 1 notch.

james_s:

--- Quote from: alsetalokin4017 on May 07, 2019, 12:20:37 am ---Now, what is really confusing is when the schematic has the pins all mixed up for routing purposes and they are labeled by their functions rather than their numbers. I think that must be done as a cruel joke by designers played on beginners.      |O

--- End quote ---


That's done for a very good reason, pins are grouped by function to enable clear, logically drawn schematics that are easy to read. I find it very annoying and cumbersome when schematics are drawn with the pins in actual physical locations, maybe it's ok for very early beginners but it would drive engineers nuts and result in ugly hard to follow schematics.

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