# Schematics (understanding and drawing them)

**URL:** <https://lookmumnocomputer.discourse.group/t/schematics-understanding-and-drawing-them/1011>\
**Category:** Uncategorized\
**Created:** [May 25, 2020, 3:08pm UTC](https://lookmumnocomputer.discourse.group/t/schematics-understanding-and-drawing-them/1011 "2020-05-25T15:08:00Z")\
**Posts on this page:** 1\
**Showing post:** 46

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**Author:** ![analogoutput](https://yyz2.discourse-cdn.com/free1/user_avatar/lookmumnocomputer.discourse.group/analogoutput/32/29663_2.png) [@analogoutput](https://lookmumnocomputer.discourse.group/u/analogoutput)\
**Post date:** [February 28, 2023, 1:27pm UTC](https://lookmumnocomputer.discourse.group/t/schematics-understanding-and-drawing-them/1011/46 "2023-02-28T13:27:29Z")

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Regarding potentiometer pin numberings:

In the KiCad footprints library, I believe all the horizontal board mount pots (ones with the shaft parallel to the PCB) have pin 1 counterclockwise and pin 3 clockwise:

![image](https://global.discourse-cdn.com/free1/uploads/lookmumnocomputer/original/3X/2/d/2dd26d6ac32700875aeb7279aa4a06d819230cba.png)

![image](https://global.discourse-cdn.com/free1/uploads/lookmumnocomputer/original/3X/b/e/be18017375c2f60c95bbff833268c44c86ee933d.png)

However, inexplicably, most of the vertical pots (shaft perpendicular to PCB) in the same library have pin 1 CW and pin 3 CCW. There are only a few exceptions including Potentiometer\_Alpha\_RD901F-40-00D\_Single\_Vertical:

 ![image](https://global.discourse-cdn.com/free1/uploads/lookmumnocomputer/original/3X/9/8/9845049135ebb47cad4677b08a42d727ec900bb3.png)

 ![image](https://global.discourse-cdn.com/free1/uploads/lookmumnocomputer/original/3X/9/b/9b381bd77dbf71222681fe6b318ad8703229d805.png)

 ![image](https://global.discourse-cdn.com/free1/uploads/lookmumnocomputer/original/3X/b/a/bac52e24ef18206474d8d99a50c5004e2d0f9b85.png)

This is really bizarre especially since if you look at for instance the Bourns PTV09A datasheet it shows the pin numbering the other way around:

![image](https://global.discourse-cdn.com/free1/uploads/lookmumnocomputer/original/3X/3/0/303a45c23c20d943f049fcc04e343cd6ae0873dd.png)

Maybe there’s some datasheet out there for some pot that has pin numbering with 1 clockwise but I don’t know of one. So I think this is _almost_ universally the accepted numbering, but it does _not_ agree with a significant number of KiCad footprints.

To make my intentions clearer I use a custom pot symbol that has an arrow indicating clockwise rotation:

![image](https://global.discourse-cdn.com/free1/uploads/lookmumnocomputer/original/3X/1/a/1aee06162ce406d07671f80007e930a316761b4e.png)

and then for vertical pots I always use footprints similar to Potentiometer\_Alpha\_RD901F-40-00D\_Single\_Vertical.

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