I ordered boards to test a new power supply design. It’s based around the National Semiconductor LM2576. This accepts 7v to 40v as input and uses switching to produce a stable 5v output.
One of the things that became apparent to me as I worked on TinyTimer and TinyPLC is that a USB power input wasn’t always convenient. I still think it is a great power source for small electronics. The wall transformers are plentiful, cheap, and have a very easy to find cable that is very durable. All qualities that are optimal for small embedded projects.
However, in some control applications it would be convenient to use whatever DC power is handy. A rectifier could be added in some cases to deal with AC sources like 24vac which is very common.
I am also looking at the LNK306PN which is essentially a power supply on a chip.
Here is an image of the prototype / testing board: