Asking for help - again. LED orientation in opto endstop

Hi, I am starting to assemble my first EVER PCB, the opto endstop v 2.1.
And I'm stuck.

Quote: "The LED must be inserted in the proper orientation. Insert the short leg (negative) into the hole closest to the flat side of the silkscreen."
Opto endstop instructions

OK, I know LEDs must be correctly oriented, and I know which is the short leg.... but what is "the hole closest to the flat side of the silkscreen", in fact, what is the silkscreen?

It seems to me this component is placed approx in the middle of one end of the board, so there isn't a hole obviously "closest" to anything....

I'm sure this is clear to many of you, so please can you translate?
Cheers,
Hazel

On the circuit board you will see that it has been printed with the names of the components, ie R1, C1 etc.

They usually have a shape representing them, rectangular for resistors and circular for capacitors etc. The LEDs have a circular shape with one side shown as flat, hence "the flat side of the silscreen"

I think its called a silk screen because its printed using silk screen printing, or at least it was at some point in the history of electronics!

Phil

Unfortunately the short leg is not always the negative. Unless you got the exact original part it is a good idea to double check where you got the LED from.

Or check with a multimeter. Most modern multimeters will light an LED on their lowest resistance range when the black lead is on the negative (cathode).

Looking at the photo on the wiki the flat is nearest the copyright text. Sometimes the diode has a flat on it to match the outline, but again it can be the other way round. Mad I know!

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[www.hydraraptor.blogspot.com]

Thanks Phil for the explanation (I know about silk-screen printing of t-shirts, but....)

OK, so I thought it all made sense - until I checked the board. The LED's shape drawn on the board appears to be pretty circular (see link to photo')
photograph of opto endstop board
so just to be sure, does the short lead go into the hole adjacent to the word "Design" on the board?

Are LED diagrams usually this subtle?

cheers,
Hazel.

Ah, you replied whilst I was typing! Thanks Chris, it is as I guessed.
And I shall go to check my LED now..

Hazel.

That silkscreen was interrupted by the holes for the component, but yeah, if you look closely, the side nearest the word "Design" is the flat side - you can see the little squarish corners in the photo. The LED's I've used had a flat side molded into the clear plastic; but as Nophead says, it's best to check.

Yes, thanks, mine didn't have a flat on the component itself, as far as I could tell, but I did manage to check them with my multimeter. I'm going to try to remember to check all my other LEDs before inserting them.
Hazel