- How does ambient temperature affect LED efficiency?
LED fixtures must be designed with junction temperature thermal management as a key component and use the correct LEDs. These products will then be robust enough to operate in most ambient temperature applications. Unlike fluorescent sources, cold temperatures do not impact the performance of LEDs.
- How do you evaluate LED products?
Lumen output is only part of the story and can be misleading. To fully evaluate an LED product one needs to review the overall system efficiency, optical control, thermal management of the LEDs, and know at what point in time the fixture will reach 30 percent lumen depreciation. Products with good optical efficiency and thermal management will be able to deliver more lumens, on average, than traditional HID products.
As the Department of Energy concluded in its Solid-State Lighting Commercial Product Testing Program:
"Until the field of SSL technologies and supporting knowledge matures, any claims regarding performance of SSL luminaires should be based on overall luminaire efficacy (i.e., from testing of the entire luminaire, including LEDs, drivers, heat sinks, optical lenses and housing), to avoid misleading buyers and causing long-term damage to the SSL market."
- Whats the difference between efficiency and efficacy?
Lighting fixture efficiency is the ratio of the total lumens exiting the fixture to the total lumens initially produced by the light source. For example, if a bare 100W incandescent lamp (light bulb) produces 1,000 lumens, and it is put into a lamp fixture that delivers 700 lumens, this would be an example of a 70% efficient fixture.
Efficacy is a term normally used in cases where the input and output units differ. In lighting, we are concerned with the amount of light (in lumens) produced by a certain amount of electricity (in watts). Efficacy = Lumens Per Watt
- Are LEDs as bright as fluorescent and incandescent?
Unlike conventional light sources such as incandescent, halogen or fluorescent, the light from an LED is directional. Because of this nature, LEDs can appear almost twice as bright as typical light sources.
- Can LEDs be dimmed?
LEDs can very easily be dimmed either by Pulse-width modulation or lowering the forward current.
- What is LED?
A light-emitting diode (LED) is a semiconductor device that emits light when electrically forward biased. The color of the emitted light depends on the composition and condition of the semiconducting material used, and can be infrared, visible or near-ultraviolet.