What do IR LEDs degrees mean

[Zululander]

I am playing with IR LEDs and receivers. A project that I am looking at speaks of a half-angle of 5 degree IR LED but I have a 30 degree IR LED. How does the half-angle affect the functioning of an IR LED?

 

[Ian Rogers]

Its the projection.. If you could see the light emitted, the angle is critical.... Most LED's, not just IR ones, have a quirky angle of radiation.

Half angle will be the degree from the max point... So a 5 degree half angle will be a 10 degree angled LED... IMHO....
If the device has a 10 degree angle.. then if misaligned by half this, the thing will not work..

I use 15 degree red LED's in my Obstruction lights... 7.5 degrees above or 7.5 degrees below, you don't notice it..

 

[gophert]

I am playing with IR LEDs and receivers. A project that I am looking at speaks of a half-angle of 5 degree IR LED but I have a 30 degree IR LED. How does the half-angle affect the functioning of an IR LED?

The smaller the angle of projection means the beam is more focused AND the spot of "light" is brighter (so it can be sensed at greater distance. However, the smaller angle (smaller projected spot) means it is more difficult to align the beam with the detector.

 

[unclejed613]

i used to make LED flashlight bulbs before LED flashlights were a thing. one of the bulb sets i sold were infrared lamps for use with night vision goggles. the set consisted of two "flood" lamps and a "narrow beam" lamp. the two floods were 30 degree, one 100mW, the other 200mW, and the narrow beam used a 5 degree 150mW. the narrow one threw a spot that was useful up to 300 meters or so. because the energy was spread out over a wider angle with the wide lamps, those were useful out to about 50 or 100 meters but you had a wider view.

 

[ronsimpson]

 

[gophert]

View attachment 117804

Looks like someone needs a more accurate protractor.

This is more like 15 and 60...

Not this...