Electronics > Beginners
Where is pin #1 for NE555P
fixit7:
I looked at the data sheet for this ne 555p chip. I can not figure out where the pin locations are.?
The picture shows a half circle on the chip which tells me nothing.
https://www.dropbox.com/s/fitler9s3jt0i64/NE555P.jpg?dl=0
As in where is pin #1 in my picture?
Thanks,
Andy
Howardlong:
The circular indent in the package points you towards pin 1, in the traditional orientation package diagram of DIP, SOIC and SSOP packages, pin 1 is almost always shown top left.
Thus, the two traditional standards for DIP are a marker at the top or a marker at the top left. Irrespective, if the chip is oriented with its marker to the top (or top left), pin 1 is ALWAYS at the top left.
To be clear in your picture’s orientation, which is at 90 degrees to a standard pinout diagram, the top row of pins is 8 7 6 5
Bottom row is 1 2 3 4.
If you turn your picture clockwise 90 degrees, the marker is at the top left, the same a standard DIP pinout diagram.
Edit: this is an interesting noob question, because it’s one of those things “everyone knows”. Except they don’t.
Edit 2: added some more details, I can’t help feeling my pudding is over egged now.
(What’s more frustrating is that for some packages, manufacturers sometimes show you the view from the bottom, not the top. I have never seen this for DIP though, markings are always shown from the top.)
james_s:
I remember having this specific problem when I was a kid. Even the otherwise excellent Forrest Mims book I had did not show this detail as I recall and the internet was not a thing then so it was not easy to find the answer. It's something that is very simple once you know it, but without knowing that pins count up counter-clockwise around the IC from the lower left corner it is not obvious.
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.
Howardlong:
--- 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?
6PTsocket:
With the notch up, looking at the top of the chip, pin 1 is to the left of the notch and the numbers go CCW around the chip. If it is an 8 pin chip, pin 8 is on the other side of the notch.
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