>shudder. Their attempt to prove that you only need
>one PIC and very few extra parts to build the
>circuit doesn't make it a good design. No
>commercial products that I have repaired use
>that system. Even the cheapest TVs use two
>resistors AND a lower resistor (voltage
>divider), so there is a finite max voltage
>expected at the semi.

The extra parts are there to comply with FCC and fire protection rules.
There are two resistors because of the maximum voltage rating on each is
not enough in 220V countries. You can over-engineer your design until it
will survive direct lightning strikes but somebody is guaranteed to do the
same cheaper and then you loose. Oh, and would you care if the dimmer
still works when you dig it out of the smoking ruins of your house ? In
general, who exactly decides when a design is 'good'. Your teacher ? He
won't pay your salary, *you* probably pay *him*. Aunt Martha who plugs the
110V device under warranty into the 220V socket for the fourth time, but
you don't want to upset her because she buys lots of equipment from you ?
Your manager ? If you use two resistors insted of one you will spend the
remaining half of your life explaining him that it had to be two. You ? Me
? Who am I to decide that.

A 'good' design is a design that is as simple as possible to do the job
(W. of Ockham), reasonably cheap, that sells for as much money as possible
and performs satisfactorily in the market, and has a return rate lower or
equal to what you have calculated when designing and budgeting it. Imho.
If at this point you will reply that a zero return rate can be achieved
then it is time to patent your perpetuum mobile plans imho ;-).

Peter

--
http://www.piclist.com hint: The list server can filter out subtopics
(like ads or off topics) for you. See http://www.piclist.com/#topics