Control/Dimming Dimming Curves

[Chris15]

So this underpins a project you'll hear about later.

Assuming a linear dimming curve, and ignoring the triac issues around the zero crossings, what's the relationship between the inputs to a dimmer (be it DMX or analogue) to the output?

Should a control input of 33% result in the RMS output voltage being 33% of the unadulterated input? Or is it that it should represent a 33% duty cycle, ie. that 33% of the time, the voltage is being output?

 

[JD]

Even on a linear curve (or lack of curve so to speak), there is not a direct relationship. ETC for example, also inputs the line voltage as a data source and adjusts the firing points to compensate for variations in line voltage. Also, the 0 to 100% line is drawn from the idle bias (or trim) at 0 to the max efficiency rating of the dimmer (in a perfect world) at 100.

In other words, 0 may equal 5% and 100 may equal 97% even on a linear "curve."