AVR-Chat

Hello folks,

I have a 230 V AC power line that is connected to a light dimmer. I want
to determine how much this signal is dimmed, e.g. what the duty cycle is
(i guess the dimmer regulates the duty cycle?). 8-Bit precision is enough
(or less as well)

Any suggestions how to connect the power line to the microcontroller?

My first thought was to connect a resistor and zener diode in series and
an optocoupler over the diode, thereby making it possible to read the
value from the other side of the optocoupler, but all optocouplers seems
to need at least 20 mA through the led which would make the resistor
suffer 4.5 watts...

Regards,

Manne Tallmarken

On Mon, 16 Jul 2007 14:33:44 +0200 (CEST) you wrote:

>Hello folks,
>
>I have a 230 V AC power line that is connected to a light dimmer. I want
>to determine how much this signal is dimmed, e.g. what the duty cycle is
>(i guess the dimmer regulates the duty cycle?). 8-Bit precision is enough
>(or less as well)
>
>Any suggestions how to connect the power line to the microcontroller?
>
>My first thought was to connect a resistor and zener diode in series and
>an optocoupler over the diode, thereby making it possible to read the
>value from the other side of the optocoupler, but all optocouplers seems
>to need at least 20 mA through the led which would make the resistor
>suffer 4.5 watts...
>
>Regards,
>
>Manne Tallmarken

In practice a lot of optocouplers will function with a lot less than 20mA. In
one circuit I use an SFH601-4 at only 2mA.
--
Ralph Hilton
http://www.ralphhilton.org
C-Meter: http://www.cmeter.org
FZAOINT http://www.fzaoint.net

>Any suggestions how to connect the power line to the microcontroller?
=========================================================

Drive a small incandescent 230V bulb in a black tube with a light sensitive resistor.
This will give a reading proportional to brightness, which is what you are interested in.


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