As an exercise Olin kindly gave me a circuit to try to analyze.  Here is what I can find in sub circuit R2, D3, C2, Q1.

I am deliberately not reading any of the previous posts on this yet until I can give this a try myself.

First the component list:
R2 2.7k resistor
D3 Zener Diode 5.6v
C2 1uF 10v capicitor
Q1 NPN Transistor

Since I had hints but nothing too specific about how and where to start, I'll have to fall back on my programming knowledge and give this a shot. If it doesn't work, I'll learn something and try a different approach.

Inputs and Outputs

Assumption: The emitter on Q1 feeds VDD on IC2.  A small current on the base of Q1, which looks like me to come from the 8.2V line after passing through R2. I'm not sure how to apply V=IR here, but from what I see the 8.2 volts passing through R2 drops to 5.6 volts which is used in both the base of Q1 and the output of the 5.6 volt power line from this power supply module.   But how is 8.2 volts dropping to 5.5?  Is because some of it is going to "leak" through R2.  

Resistors limit current, correct? So passing 5V through a resistor should yield 5V on the other side? Or did I get this wrong.

So here is one point that I'm stuck on.  The data sheet for the Pic10F204 says 0 - +6.5 volts.  But what I'm seeing is VDD gets 8.2V. 

The zener at D3 and C2 have me stumped.  I've already been through a lot of Mims' books and other electronics books to get this far.  I'll go to E&E next.   I love that book!

Any corrections in my logic, just to make sure I'm on the right path, would be greatly appreciated Olin.  

I cannot tell you how grateful I am that you're taking this bit of time to help me get over my learning curve.

Kind regards,
Lindy



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