Hi Dave

Thanks for tip, I was going to get eyes in on the local sub-station but will do so tomorrow ;-) and update as soon as possible :-)

The quotation is actually from a Microchip appnote TB008 , the paragraph is just above figure 3. in the appnote. [HTML]http://ww1.microchip.com/downloads/en/AppNotes/91008C.pdf[/HTML]

Ok the project is for the PIR-sensor based security lights, I need to tap into the PIR and replace the existing LDR and sensor circuit which are also transformer-less and triac controlled. Each sensor light PIC transmit back to a central PIC.

Given the space I have I cannot fit a transformer based supply into the housing or wall point (someone did a good job installing them) and there is no way I can mount the circuit externally.
So transformer-less it is !
I have seen circuits aplenty on the web yet it seems most are common live and also mainly for 120VAC it seems.
Some even with dual fuses (one on LIVE and one on NEUTRAL!)

So it seems there is quite a lot of confusion in this arena and for good reason I suppose, fear of death being the ultimate reason people shy away and of course once bitten twice shy(being shocked into submission certainly shys people away).

So my quest was to research the topic of transformer-less supplies before I dive into anything like building one only to encounter serious injury and the possibility of my circuit frying !

Nothing I have seen out on the web quite explains how one should wire things up on the pic if you're using a transformer-less PSU.
So appnotes are created and design note etc ... but the very simple steps seem to be missing, the questions (FAQ's) and their solutions.

So how do we find news ways of doing things if we are stuck designing only in the confines of a transformer-based supply.

In the early years I remember learning about the effects of capacitive, inductive and resistive circuits.
For example :
With a CAPACITIVE circuit, A current will flow through the circuit, first in one direction, then in the other.
No current actually flows through the capacitor. Electrons build up on the one plate and are drained off from the other plate in very rapid succession, giving the impression that the current flows through the insulator separating the plates.
However, a capacitor in an AC circuit does offer resistance to the overall current flow. We define a quantity called the CAPACITIVE REACTANCE, Xc,
In the designs I have seen, people place and swop around the components as the desire almost as though it's a little slap-dash design which may or may not work and your mileage may vary.

For example, I changed my original circuit design around to make it safer (which was a copy and make-up of the Microchip appnotes (or close to it ) , why would they suggest such an unsafe circuit I wonder ?
Then I keep getting told to use the Microchip designs ... yes I would love to but are they the safest ? And most if not all of them are for 120VAC without worked examples for 220V or 230V.
You may have already noted that there COMMON HOT(LIVE) and COMMON NEUTRAL transformer-less supplies.
So after having changed the initial part of the circuit to make it a common neutral supply , this raised more questions
what then? , what else needs to be changed ?
Are the diodes and other components correctly setup and placed the correct way around ?

And as regards the benefits... well
1. it is space saving,
2. is cost (the tiny transformers are extremely expensive here) and
3. is that I can go extremely small if I use SMD components not so ?

I have to put the same circuit in about 15 lights.
If you do manage to see a mistake please let me know.

Anyways that it from me.. I hope that exaplins it so far :-

Kind regards

Dennis