Tried this and the results are:You are right, 12 V can fry a LED, even when set up to measure LED Vf. If we should mistakenly connect pot
to O ohms to start rather than max R, then Poof, LED & or mA meter. That is why I almost always add some resistance in series with a pot, smallest R that will prevent damage by itself.
Simple setup to measure LED Vf, generally used to sort Vf of many LEDs into piles of same V, then if used in series strings, the strings can be made up of low V, med. V & high V so that all strings are = V. The blue LED is used for protection of reversed DUT, device under test. When testing white LEDs, for blue LED might use a white & red LED in series to give about 5 V, which should be safe for a reversed LED. The 470 ohm R could be made from a combination
of series & parallel Rs to give desired test current.
View attachment 108474
View attachment 108474
12.41v supply
463ohms resistor
1.87 vf
Tried this and the results are:You are right, 12 V can fry a LED, even when set up to measure LED Vf. If we should mistakenly connect pot
to O ohms to start rather than max R, then Poof, LED & or mA meter. That is why I almost always add some resistance in series with a pot, smallest R that will prevent damage by itself.
Simple setup to measure LED Vf, generally used to sort Vf of many LEDs into piles of same V, then if used in series strings, the strings can be made up of low V, med. V & high V so that all strings are = V. The blue LED is used for protection of reversed DUT, device under test. When testing white LEDs, for blue LED might use a white & red LED in series to give about 5 V, which should be safe for a reversed LED. The 470 ohm R could be made from a combination
of series & parallel Rs to give desired test current.
View attachment 108474
View attachment 108474
supply 12.41v
resistor 463ohms
volt meter reading 1.87v
I tried 23 LED's and results follow:
1 red & 1 green : 1.88v
5 red, 6 green & 3 yellow :1.87v
1 red & 5 yellow : 1.86v