Simple rectifier for MCU PSU

A friend of mine told me about simple rectifier configuration that’s usually deployed in white goods (iron, washing machine, vacuum cleaner, etc). You can view the explanation here and here. It’s very interesting to know that you actually don’t need a big transformer or even switching PSU to supply your MCU from AC source.

Here’s my schematic for my own board:

Linear PSU Efficiency Quiz

Moving out to Singapore, I’ve become nearly disabled. No solder, no board, no multimeter, etc. Actually, my employer provides me with the tools, but I’m kinda hesitated to use it for my own personal use. I guess I have to buy it for my own later.

Anyway, since I’ve got nothing to do this Sunday, I’ve come up with quizzes, just to test my electronic insanity. What is the efficiency of these ugly linear PSUs ?

Simple Zener Rectifier

I’d say its efficiency is 17.59%..Here’s another one:

Current Feedback Linear Rectifier

My insanity said that it’s efficiency is 17.64%.

Is there anyone who has different answer than me ?

Programming Timeout under FreeRTOS

It seems like the FreeRTOS has some support to program a timeout, but unpublished anywhere. I’ve checked the FreeRTOS source code, regarding the usage, and it seems like it’s quite safe to use it under user’s application.

Here’s what I’ve found: