LED Dimming Compatibility

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    LED Light Level Definitions
    Undesirable level change of lighting fixtures, especially LED lights, can be caused by several factors. The lighting industry commonly uses the word “flicker” to describe any undesirable level change, regardless of when or why it occurs. This makes accurately describing a condition extremely challenging. Our goal is to establish a set of clear descriptive terms to define the most common types of undesirable level change to aid in the correction of problems in the field.

    General Technical Terms
    Control State The status of the control device/level when an undesirable level change occurs
    • Dynamic control state
    The level change occurs in conjunction with a button press, fader use, preset or sensor activation, etc.
    • Static control state
    The level change is not triggered by a button press, fader use, preset or sensor activation, etc.
    Dimmable Range Ratio of minimum stable level to maximum level of measured light, usually expressed as a percentage.
    Fade A gradual change of control state or fixture output.
    Fire The process of a ballast powering LEDs once it receives its minimum required voltage.
    Full Fixture is outputting at 100% of its capacity.
    Ideal Condition A smooth and continuous dimming curve with no interruptions.
    Operation An automated or manual change of the control state.
    Pop An instantaneous change of fixture output.
    Steady Constant control or fixture output.
    Switch An instantaneous change of control state.
    Threshold The control level at which a dimmer or relay turns on.
    • Minimum Scale Voltage
    The voltage a dimmer turns on to when the control level exceeds the threshold.
    Zero Cross The moments in an AC sinewave where the wave form crosses the x-axis as the value alternates between positive and negative.
    Zero Cross Blanking Time/SCR Off Time The amount of time before and after the point where voltage crosses zero in which a firing signal is not sent to the power cube. Default time CEM+/3 DRd and SmartPack is 500µs. With Legacy Unison & CEM Classic the zero cross blanking time is fixed time at 200µs.

    Undesirable States
    Bounce The light level fades past its intended output level and then fades back to its intended level.
    Dead Travel During a controlled fade the control level is moving up or down but the light level remains steady; usually occurs at either end of the fade operation.
    • Flat Spot
    A section of control levels in a fade where dead travel occurs (e.g. “We have a flat spot between 40% and 60% on our fader”).
    Death Gasp The light level fades down smoothly except for a pop to a higher level just before it goes out.
    Delay On/Off An undesired delay after the activation of control before the fixture outputs perceivable light.
    Drop Out A state where the light level drops to zero then back to the desired level.
    Ghost A state where the control level is at zero but there is still a perceivable light output from the fixture.
    Pop to Full An output state where the light level pops to full then back to the desired level.
    Popcorn Fixtures on the same circuit do not turn on simultaneously.
    Stepping ("steppy") Dimmer output during a fade that appears as perceivable jumps rather than a smooth transition.
    Shimmer A state where the output light appears to quiver or vibrate as though one is looking at heat waves or a mirage. This state is usually more common at lower output levels.
    Strobe A state where the fixture outputs series of extremely quick flashes; can be constant or intermittent.