Take the 2-minute tour ×
Electrical Engineering Stack Exchange is a question and answer site for electronics and electrical engineering professionals, students, and enthusiasts. It's 100% free, no registration required.

enter image description here

Is the capsule's straight face visible? Or the round one? Is that top view or bottom view?

Do all datasheets use the same orientation?

This is the datasheet. I'm not looking for an answer specific to this datasheet. I want to know how to identify pins when there's a representation like this shown. Some datasheets use 3D images with pin labels, but not this one.

share|improve this question
1  
It MOSTLY works as others say here. BUT on occasions the presentation is non standard and you MUST check in every case that what you see is self consistent or you will get caught out. Front and bottom view is the norm. Pins 123 left to right is the norm. 321 is not unknown. Anything the mind can conceive MAY happen. just to keep you awake, occasionally it's wrong :-). –  Russell McMahon Aug 2 at 11:34
1  
Just the bottom view alone is clear by itself. –  Olin Lathrop Aug 2 at 14:20
    
@Cornelius Looking up a datasheet another IC in the same package but with more readable drawings is a valid strategy. When dealing with standard IC packages, it works most of the time. –  Nick Alexeev Aug 2 at 17:41

2 Answers 2

up vote 10 down vote accepted

There are two common projection methods for technical drawings.

First-angle projection
First-angle projection is as if the object were sitting on the paper and, from the "face" (front) view, it is rolled to the right to show the left side or rolled up to show its bottom.

enter image description here

enter image description here

Third-angle projection
Third-angle is as if the object were a box to be unfolded. If we unfold the box so that the front view is in the center of the two arms, then the top view is above it, the bottom view is below it, the left view is to the left, and the right view is to the right.

enter image description here

enter image description here

This is actually the projection method used in the example data sheet. I marked the two planes that were used.

So what about the question "how do I know what method was used"?

On engineering drawings, the projection angle actually "should be" denoted by an international symbol consisting of a truncated cone, respectively for first-angle and third-angle (standard in the USA, Japan , Canada, and Australia).

enter image description here

As this "indicator" is often not present, the other option you have is to actually look at the planes and evaluate the view by looking at the properties of the object as the answer from Vladimir Cravero already pointed out. I would assume that the indication is often omitted because/when the projection type can already be identified unambiguously this way.

Source and additional information.

share|improve this answer
2  
+1, that's very interesting –  Vladimir Cravero Aug 2 at 13:05

The one you see is the straight face, and that's a bottom view.

Look closely at the images:

  • on the first one you see two couples of vertical lines: the two internal ones can be visible only if you look at the transistor with the straight face facing you. If it was rotated by 180° along the vertical axis you would only see a rectangle with no internal vertical lines.

  • on the second one you should just apply the same principle: if it was a top view the pins would not be visible, so that's a bottom view indeed.

The general rule then is: grab the component and try to orient it like the drawings, there is only one possibility, that's the right one. The principle is: think of what is visible and what is not. I'm not sure if I've actually seen this in a datasheet, but sometimes dashed lines are used to draw not visible parts. The same bottom view with dashed pin outlines would have been a top view.

share|improve this answer

Your Answer

 
discard

By posting your answer, you agree to the privacy policy and terms of service.

Not the answer you're looking for? Browse other questions tagged or ask your own question.