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A clearer schematic and application note is available here...(http://www.st.com/content/st_com/en...olution-eval-boards/steval-ild005v1.html)...I would have uploaded the application note but the file is too large for this forum.
http://www.st.com/content/ccc/resou...df/jcr:content/translations/en.DM00161788.pdf
The schematic link on their website seems to be down, but the above link is for the datasheet which shows the schematic on page two.
Is the circuit something already in use that you want to scab on to?
As a bit of extra information this dimmer circuit is perfect for use in the UK where typical wiring installations do not have a neutral conductor available at the point of installation (the light back box)
What do you have coming into the box? Power has to come in on one wire and leave on another, the names may be different, but physics are the same. I thought UK has red (live) and green/yellow earth as well as a blue neutral?
What I was going to mention was a small transformer and rectifier setup if you had the space
Pardon my ignorance, I will have to look into uk wiring more - I forgot you have 230V. In the states, we have split phase, we use two 120 legs to derive our 240v and in our circuits for 240, its two black conductors each are live with 120v and one ground earth. Each 120 leg crosses over the other wire for return. I would assume the same happens in your setup so I am not sure why the neutral would be needed.Typically at the light switch in the wall there will be an unswitched live conductor and a switched live conductor, these both connect into the light switch (this is called 2-wire configuration which is most common in the UK). These would then be routed to the lamp in the ceiling where the neutral is available therefore completing the circuit. It is common for an earth to be present at the light switch but this cannot be used as the circuits return path.
Diodes never behave ideally so if you have two in parallel, chances are one of them will have a lower forward voltage and will end up taking all the current.is it too simplistic to suggest a second zener diode in parallel to clamp the sub-circuits voltage to a lower level?
About the same as in the US. Usually we have unswitched line and neutral coming into the switch box, and switched line and unswitched neutral going out to the light. The two neutrals are joined together inside the box with a wire nut.Typically at the light switch in the wall there will be an unswitched live conductor and a switched live conductor, these both connect into the light switch (this is called 2-wire configuration which is most common in the UK). These would then be routed to the lamp in the ceiling where the neutral is available therefore completing the circuit.
Yes. Ohm's Law. With the AC peak voltage and the equivalent of all of those 12 K resistors, you can calculate the peak current available at the zener for both the dimmer circuit and whatever else you want to run. Hint - the guys at ST probably have designed the circuit for exactly what the circuit needs at low line voltage.The circuit shown used a zener diode to clamp the voltage to 15V at the output side of the rectifier circuit, is it too simplistic to suggest a second zener diode in parallel to clamp the sub-circuits voltage to a lower level?
With the AC peak voltage and the equivalent of all of those 12 K resistors, you can calculate the peak current available at the zener for both the dimmer circuit and whatever else you want to run. Hint - the guys at ST probably have designed the circuit for exactly what the circuit needs at low line voltage.
One could get hung by the authorities if this "generated" low voltage was brought out into the real world without approved isolation.