Paul said:

  (lots skipped)

>  Yes.  It doesn't solve the isolation problem at all.  Best for small,
>encapsulated products such as stand-alone knob-operated dimmers/ power
>controllers.

  This is exactly the way it was used in one of our products.

>>>> how about this solution
>>> http://www.vertonet.com/members/pvh/scr.pdf
>>> get power for the pic from the other side of the load with diode, cap
>>> and resistor in series.
>
>  Did *no-one* notice the blooper here?  Did anyone look?
>
>  D5 is on the *wrong* side of D6.

  Peter's circuit is slightly different from the circuit I used. In
  my application C1 was omitted. R2 was between C2 and D5, i.e.,
  C2 would charge up to peak line voltage and R2 limited current
  through D5. Reflects the reality that if you only need a few mA in
  a very price-driven application, and you don't have a user interface
  to isolate, power resistors are cheaper than transformers.

  My reply to the original query outlined the disadvantages. It's
  certainly not a universal solution.

  Reg Neale