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CMB24 Dimming curves


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Hi all,

I picked up some LOR dumb strips and CMB24s at the mad grab sale. I have seen many posts regarding the use of dimming curves for LEDs on LOR1600 contollers, but nothing regarding the CMB24. I tried to go into the advanced configuration in the hardware configuration utility and it says it does not support advanced configuration. Since the dumb strips are LED, wouldn't the same issues requiring dimming curves on the LOR1600s still apply? I have tried some fades and dimming and it does't look linear like incandescents.

Sorry if this is a stupid question, I am a long time incandescent user with LOR and new to the LEDs.



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Anything attached to a CMB24D is running in DC to start with. LED strings that you attach to your 16 Channel AC controllers would need the dimming curves, as there is some AC/DC action going on there. (Someone smarter than I can explain that part of it.)


Thus dimming curves on the CMB24D wouldn't be needed.

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Don't think I am any smarter than Mr. Don, but perhaps I can help you here.


With the AC controllers the reason you have dimming curves has to do with the fact that when you phase angle control AC to your lights, (which is what the AC controllers do), the relationship between the on time and off time is not a linear power function.   Meaning that in a given time period (one AC cycle) if you have 50% ON time and 50% OFF time,  with an AC controller, the average output voltage will not be 50%. Not even close.  The "dimming curve" (square law curve for the old theater techs) is to help correct the relationship between the actual light output you realize with your eyes and the setting level you are calling for in the controller.  It is a compensation method to bring the two closer together.


If on the other hand you have a DC Pulse Width Modulation (PWM) controller with the same 50% ON time and 50% OFF time, your average will be 50%. The relationship between the brightness level your eye realizes and what you are calling for from the controller is much closer.  (LEDs are pretty linear devices for the most part)  For this reason there really isn't a "dimming curve" for the PWM controllers.  There is "Gamma Correction" (a whole other subject) available in some controllers, but not these. 


Not sure I explained that well, but there is my shot at it..  Hope that helps



Edited by plasmadrive
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