My original questions:

>I was thinking of using an 'F84 for serial controlled 240Vac lamp dimmer.
>Does anyone know how many steps you need for really smooth fade up/down ?
>I thought 256 discrete levels (1 byte) would do but I imagine that some
>sort of look-up table is required so that 'level 127' for example will
>actually be half brightness due to the lamp's non-linearity. Levels 0-255
>makes it easy to assign min/max/etc levels as a byte each. I realise that
>each type of lamp will have a different power/intensity curve but is there
>a general purpose 'average' type of curve available out there ?
>Regards...

Dennis Plunkett wrote:

>I have seen some interesting comments on your problem. Yes the basic
>response that the output is log is correct, however I do assume that it is
>Yellow light that your controlling? If this is so, you will have to look at
>perception of brightness. But as a simple rule of thumb (Here come the
>"critics"), the eye will see only some 16 different brightness levels with
>the majority of the sensitivity being in the low light area (Electronic
>score boards like that at the MCG and SCG and Waverly park use only some 16
>(Waverly park) to 48 (MCG and SCG)). However a smooth increase in brightness
>from off to fully on will require some 64 steps in your case (This assumes
>that you are not using fixed wattage lights, Note that other colours like
>GREEN and BLUE will require a very different curve to that of FULL YELLOW
>and RED).

The plot continues !

All I want to do is control standard household lighting. (home automation)
My aim is to go between 0% and 100% smoothly. (with no perceptible steps)
Harold Hallikainen kindly gave me some information on how to calculate the
curve points and I will follow that up. I've since seen a dimmer project on
the PicPoint page but have not looked closely at it yet. Thanks so far !
Regards...   :-)

_______________________________________________________________
Dave Duffy         Audio Visual Devices           AVD@uq.net.au
Unit 8, 9-11 Trade Street, Cleveland, Queensland 4163 Australia
Phone: +61 7 38210362                 Facsimile: +61 7 38210281
_______________________________________________________________