At 05:31 PM 1/05/98 +1000, you wrote:
>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...
>
>_________________________________________________________________
>Dave Duffy      Audio Visual Devices        E-mail: AVD@uq.net.au
>Phone: +61 7 38210362                   Facsimile: +61 7 38210281
>Unit 8, 9-11 Trade Street, Cleveland, Queensland  4163  Australia
>_________________________________________________________________
>
>
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
the number of lamps being controlled, as this and distance also will change
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).


Dennis