JChenault
Well-Known Member
One of the most irksome issues ( at least to my eye) is the bump in led fixtures at the start of the fade. Most fixtures that I have been able to play with have a noticeable bump as they move from 'Off' to 'Barely On'.
Many years ago at ( I believe) a USITT session, I saw a simple set up which consisted of an LED bulb, battery, and potentiometer. When the potentiometer was turned so there was no voltage the LED was off. As you turned it up, the LED ramped up with no bump at the low level.
My understanding is dimming for theatrical fixtures is done by a switching power supply that switches the full voltage driving the LED on and off very quickly. For a low level you leave in 'on' for a much shorter time slice than a higher level.
My question. If varying the voltage ( not slicing it up ) does give you a smoother curve - why don't the manufacturers build power supplies and electronics that vary the voltage, instead of switching it on and off very quickly?
I suspect there is a good reason for this design approach ( or my understanding is flawed) - I'm just curious for the rationale.
Thanks
Many years ago at ( I believe) a USITT session, I saw a simple set up which consisted of an LED bulb, battery, and potentiometer. When the potentiometer was turned so there was no voltage the LED was off. As you turned it up, the LED ramped up with no bump at the low level.
My understanding is dimming for theatrical fixtures is done by a switching power supply that switches the full voltage driving the LED on and off very quickly. For a low level you leave in 'on' for a much shorter time slice than a higher level.
My question. If varying the voltage ( not slicing it up ) does give you a smoother curve - why don't the manufacturers build power supplies and electronics that vary the voltage, instead of switching it on and off very quickly?
I suspect there is a good reason for this design approach ( or my understanding is flawed) - I'm just curious for the rationale.
Thanks