Yep, like anonymouse said, fuse in the neutral is bad!

If you really *must* build a transformerless supply, goto the document I referenced in post #17, scroll down to page 10, figure 10 and build it just like that. They've already figured out the right way.

Correctly designed transformerless supplies are plenty safe, especially since the commercial devices that usually contain them are invariably well sealed in a well insulated (plastic) housing to keep curious fingers away. Lots of insulation between the device and the user is the key.

But most of my projects involve a lot of testing, fiddling, finger poking, and experimentation (with the guts open and exposed), so most of the time I much prefer a good isolated supply.
I buy little transformers 10 at a time for under $3 each and don't have to worry about what parts are "hot" when I connect my 'scope ground or poke at a part with my finger.

If the size and weight of your project is REALLY critical (but if you're sending it up in a rocket, it probably won't be mains powered), or if you're building a product by the 1000's where saving $1 worth of parts becomes a pretty big deal, then maybe xformerless is the way to go. But for most applications (especially hobbiest) I have to ask... Why? What's to be gained that offsets the risks?

So... why do you want a xformerless supply? What benefits does it have for your project?


steve