Led cathode and anode series#

Seeing the larger 'heatsink' pad you know right away which is the cathode. With clear LED's you can tell if they're marked correctly or not. I've bought LED's from China that had the cathode marked on the wrong end. Since is working with an SMT LED that is either poorly or not marked for polarity, this rule will aid in determining which is which. Still, with SMT and PTH, it has always been consistent as per the description I've given. Since I don't have experience with LED TV's I bow to your experience. However, 30 years inspecting electronics, if you have an LED that is poorly, or not marked, you determined the cathode by the larger heatsink. This should provide enough light output to identify correct orientation, but low enough current and voltage that it won't damage anything unless you leave it hooked up backwards for a long time (and probably not even then.)ĮBEOWLF, i did what you said and found the polarity.Ĭlick to expand.I stand corrected by the voice of experience.

Led cathode and anode series#

Then add a 1k resistor in series with that, so your worst case short circuit current is ~3mA and your LED current when oriented properly will be around 1mA. I would probably try 2 fresh AA or AAA batteries in series, which will provide 3-3.3V. If you get, or make, a low voltage power supply with a current limit that's low enough to protect the diodes, you can simply try both ways and make a note of what works. LEDs often have relatively low reverse breakdown voltages, so you have to be careful not to reverse bias them at too high a voltage (I've heard that a 5V limit is fairly common, but I don't know if that's true.) Having said that, you can probably just find your answer with some careful experimentation. If there's no datasheet available, I'm not buying it! Hassles like this are one of the reasons to only buy real parts from reputable distributors.