Re: Controlling Holiday Lights

[Marc_F_Hult <MFHult@xxxxxxxxxxxxxxxxxxxxx>]

On Sat, 28 Oct 2006 00:05:44 -0600, sylvan butler
<ZsdbUse1+noZs_0610@xxxxxxxxxxxxxxxxxxxxx> wrote in message
<slrnek5spo.vse.ZsdbUse1+noZs_0610@xxxxxxxxxxxxxxx>:

>On Wed, 25 Oct 2006 02:37:15 -0400, Robert L Bass <robertbass1@xxxxxxxxxxx>
wrote:
>>> And the DMX dimmers actually control the light how?
>>
>> Most use triacs.
>
>Yup.  And the triac is controlled by a microprocessor switching the gate
>current on and off at least 120 times per second.
>
>Of course, you (Robert) are responding to a message intended for
>Marc.  :)
>
>> I understand you.  I'm fairly certain Marc does, too.
>
>I am confident he does not.
>
>> FWIW, Marc has built a DMX-512 compatible lighting controller for home use.
>
>I wonder if he created the software that actually runs in the
>microcontrollers inside each dimmer / load controller...
>
>sdb

At first I thought sylvan might just not be explaining himself well, but it
now seems more likely that he doesn't understand the fundamentals.

For folks interested in _actually_ creating dimmers using microcontrollers or
analog techniques, I created a link to a spreadsheet on my web site that I
prepared about five years ago:

http://www.econtrol.org/dimmers/TRIACDimmerCalcs_MFHult.pdf

This spreadsheet solves the equations that provide the numerical values to
program the delay-after-zero-crossing for a TRIAC-based dimmer either by
bit-banging with a microcontroller or other processor including a PC or with
an analog comparator.

It provides tables and graphs of:

0-10vdc control signal, Vdc
DMX512 0-255 value, also sequence number for dimmer steps in dimmer curves
Fraction of AC cycle
Phase angle, degrees
Phase angle, radians
Delay after zero-crossing, milliseconds
Output voltage, Vrms
Relative luminous intensity for a typical tungsten lamp, %

Email me if you want the .xls version (a .pdf is posted).

'Course neither the equations nor the data has much meaning for sylvan who
claims to create high-resolution, flicker-free control of TRIAC dimmers
_without_ synchronization to the powerline with a 1000hz fixed-frequency
trigger!

... Marc
Marc_F_Hult
www.ECOntrol.org