The new XLamp XP-E2 LEDs from Cree are claimed to deliver more lumens per watt and lumens per dollar to lower system costs for existing XP-E and XP-G designs. The new LEDs can increase the light output of existing XP-E designs at the same cost and power or reduce the system cost with fewer LEDs, enabling lighting manufacturers to deliver better lighting systems with minimal redesign.
The LEDs have the standard XP footprint (3.45 x 3.45 mm) and are optically compatible with all XP LED versions, including the popular XP-E and XP-G. The LEDs generate cool white light (6000 K) at up to 128 lm/W at 350 mA and 85 °C or 143 lm/W at 350 mA and 25 °C and are suitable for a broad spectrum of high-lumen applications for indoor and outdoor lighting, portable lighting and lamp retrofits and. [via]
New LEDs Double Lumens per Dollar - [Link]
Jack Shandle writes:
LED-based lighting has many advantages including a small footprint, exceptionally long lifetimes and excellent lighting efficacy in lumens per watt. As LEDs have become popular, the challenges of designing with them have become more evident – with thermal management topping the list.
The challenge begins with the source itself. High-powered LEDs do not generate infrared radiation, which is the primary way competing light sources dissipate energy that is not visible light. Instead, 75 to 85 percent of energy used to drive an LED is converted to heat, compared to 42 percent for a typical linear fluorescent, 37 percent for a metal halide bulb, and only 19 percent for an incandescent light source. In LED-based system designs, this heat must be conducted from the LED die to heat sinks, the circuit board, housings or luminaires. In addition, power dissipation in other parts of the system, such as the power supply, must be minimized.
ABCs of LED Thermal Management - [Link]
Measurement of light intensity is a prime necessity in several occasions. The diversity of such needs make their way to various branches of physics and engineering as well as in media. For instance, in engineering, such kinds of measurements are needed to design optimum lighting conditions of a room. In photography, light intensity measurements ensure good quality pictures by determining the right exposure. Wiring a phototransistor or a light-dependent-resistor (LDR) with an analogue LED voltmeter chip like the LM3914 or even to a microcontroller and displaying the ADC values is a pretty simple technique of measuring light intensity. The bad part of this technique is that these simple and amateur-level devices can only measure relative intensity of light and are unable to provide measurements on an absolute scale. However, with a precise knowledge of the transfer characteristic (resistance vs light intensity) of the LDR it is possible to relate the LDR output to the intensity of light in standard unit. In case the LDR characteristic is unknown or unreliable, you can still calibrate the sensor output by using a variable light source and an external reference photometer. This project is about a microcontroller based light intensity meter where an LDR light sensor is calibrated against an external photometer to obtain the intensity of incoming light in the unit of lux. The lux is the SI unitm of illuminance and luminous emittance, and measures lumens per square meter (lm/m2). The microcontroller used in this project is ATMega8L and its firmware is written using mikroElektronika’s MikroC Pro for AVR compiler.
Building a digital light meter with a calibrated LDR - [Link]
Cree, Inc. reports another industry-best efficacy record of 231 lumens per watt for a white power LED. This result is a significant advance beyond Cree’s previous industry record and further demonstrates how Cree’s relentless innovation continues to push the boundaries of what is possible with LED lighting. [via]
231 Lumen per watt LED shatters LED efficacy records - [Link]