At 02:46 PM 5/4/98 +1000, you wrote:
>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
>_______________________________________________________________
>


Using a 100 tap xicor eepot under control of a C84 I have dimmed a 20W 12V
halogen lamp from nil to full on, the changes (obviously) appear smooth,
with no problems at all.
Hope this helps.
rob
-----------------------------------
Rob Symmans

Lions Eye Institute
Lasers and BioEngineering
2 Verdun Street
Nedlands 6009
Western Australia
Tel 08 9381 0754   Fax 08 9381 0700
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