Is there any advantage of using a AC-DC switching vs transformer (linear)wall wart? Of course, the switching one is much smaller and lighter weight per rating, but costs more. I will use these for powering various LED projects along with 78xx regulators and filter caps. Thanks!

 

Your LED's wont mind any residual noise that a switcher might leave in its output, so the main criterion might be finding the wart that has some capacity that is a bit greater than your projected load.

 

The switcher types usually have a regulated output. The simple transformer only types usually have a large variation in output voltage depending on load. So if you use a switcher type, you might not need a 78xx regulator if you can find a wart that already puts out the voltage you need.

 

The switchers, in addition to being regulated, also tend to put out more current than regular unit per weight by a large margin. With applications where noise is not an issue this is a real bonus, and even with sensitive applications it isn't that hard to filter the DC.

Overall I think very highly of them.

 

Thanks guys! I have a 100-240v. 50-60hz 12vdc 1.0 amp switcher wall wart that I am using on a LED sequencing circuit, but it does not work properly unless I put a .33uf or a .01uf cap across the 12v wart output. Why is this?

 

Something that wasn't mentioned as a disadvantage, many wall warts assume a certain loading. You must have the minimum load or they don't work as predicted.

 

Something that wasn't mentioned as a disadvantage, many wall warts assume a certain loading. You must have the minimum load or they don't work as predicted.

I said "The simple transformer only types usually have a large variation in output voltage depending on load.". I didn't explicitly say that it is a disadvantage; I left that up to the reader to figure out.

On the other hand, I haven't seen any switcher types that malfunctioned without a load. I wonder if there's something wrong with the one the OP is using?