I was just reading the posting guidelines in the general electronics forum, and it mentioned several items that are not allowed for discussion. One of them is a transformer less power supply. Another is LEDs to mains. I'm just wondering what these two items are. I mean, what about a power supply that doesn't have a transformer makes it something that shouldn't be discussed? Also, what is meant by LED to mains? As in plugging a LED directly into the wall?

I'm not being critical in any way of the guidelines. I just don't know what these two things are so I don't know what their significance is.

Thanks!

 

in general transformer can be used (among other things) for galvanic isolation between primary and secondary circuit. just because circuit uses transfomer, it does not mean that there are parts of circuit isolated from each other. issue with transformerless power supplies are just that - lack of insulation. as a result, main problem is risk of having inexperienced forum user messing with something they are not ready for and getting exposed to potentially dangerous levels. such things can cause harm to individuals, be liability and have negative impact on reputation of forum. since most forum users are tinkerers/ hobbyists, banning sensitive topics is done as a precaution, nobody here knows if you are really 12 or 72 year old, or what you know or don't, if you are just trolling or not. just see how many of discussed topics have circuits that don't even use proper symbols. certain topics just don't get old such as anything with LEDs. of course powering LEDs from mains is possible (with or without isolation) but it is safer if this is left to those that do not need forum help on such topics.

 

It is definitely a catch 22, if you have to ask you should not be doing it, as it will be unsafe for beginners.