The best way to figure this out is to use a volt meter to measure the voltage from the wires take note which is the positive side. The using a desk power supply with the current way down so you don’t blow the LED set the voltage tag the LED noting which side again is the positive. As soon as you get a glow then you know which way to wire it back up.
If you carefully take the back side clip off you should see a flat side that is the physical way to tell
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Here is an example spec sheet for the LED unit [https://www.thorlabs.com/drawings/3ba8d4756d1fb580-1748B28A-BAB4-F460-EF36BAB444A11927/LED940E-SpecSheet.pdf|Ultra Bright NIR LED] note the current and physical case as that is typical for these LED’s
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Here is an example spec sheet for the LED unit [link|https://www.thorlabs.com/drawings/3ba8d4756d1fb580-1748B28A-BAB4-F460-EF36BAB444A11927/LED940E-SpecSheet.pdf|Ultra Bright NIR LED] note the power and physical case as that is typical for these LED’s
The best way to figure this out is to use a volt meter to measure the voltage from the wires take note which is the positive side. The using a desk power supply with the current way down so you don’t blow the LED set the voltage tag the LED noting which side again is the positive. As soon as you get a glow then you know which way to wire it back up.
If you carefully take the back side clip off you should see a flat side that is the physical way to tell
Here is an example spec sheet for the LED unit [https://www.thorlabs.com/drawings/3ba8d4756d1fb580-1748B28A-BAB4-F460-EF36BAB444A11927/LED940E-SpecSheet.pdf|Ultra Bright NIR LED] note the current and physical case as that is typical for these LED’s