Mains indicator LEDs

[plugwash]

I don't know the precise standard these things are built to, but I imagine the choice often comes down to "we can either buy an expensive part where the manufacturer gives us guarantees about failure modes, or we can use more parts such that the failure of any one part is not catastrophic".

 

[DetlefSchmitz]

Are you implying that the zener breakdown voltage of an LED is going to be about 5 V in all cases?

Given that that's all the data sheet bothers to specify, we can only assume that. One isn't exactly intended to use it like that. In reality the LED either will breakdown, in which case what I said applies, or it won't, in which case the LED will be even safer. As I implied earlier, I wouldn't have designed it this way, because it makes use of properties of the components beyond what appears in the data sheets. However there's no obvious other reason not to do it.

 

[JohnW2]

Given that that's all the data sheet bothers to specify, we can only assume that.

Yes, one might expect/'assume' that.

However, I've just had a play with a handful of LEDs (of a variety of sizes and colours) and all but on ehas a reverse breakdown ('zener') voltage greater than 30 V (the highest my bench PSU goes). The one exception was a small green one, which appeared to have a 'zener' voltage of about 15 V. None of them came to any harm as a result of application of 30 V (current limited by a 10 kΩ resistor). When I have some moments, I'll use a much high voltage source to ascertain what the breakdown voltages actually are.

It therefore seems that, at least for most LEDs, the specified 5V "maximum reverse voltage" may just be a (probably very 'conservative') arbitrary number pulled out of the air?

It is perhaps surprising that 'they' don't make (maybe they do?) LEDs with integral high-PIV diodes?

Kind Regards, John