The “LEDagon” project bundles together different solid state lighting technologies with thermal management solutions, PCBs, sensors and other electronic components. With the development of this cooperation project, Arrow Electronics, Cree, Häusermann and Kathrein Austria are linking complex competences in order to create a solution that is unique in the sphere of LED lighting.
LEDagon is based on the copper/FR4 PCB technology HSMtec developed by Häusermann. This makes it possible to combine maximum thermal performance, multi-dimensional product and PCB design together with control electronics on standard FR4 printed circuit boards. Moreover, LEDagon features XLamp High Power LEDs from Cree. The Cree XLamp XM-L LED is among one of the best white single-chip high-performance LED currently on the market. It is very efficient and can deliver 1000 lumens at 100lm/W. With a large beam angle, symmetrical design, unlimited floor life and electrically neutral basis the XLamp XM-L LEDs can be utilised for entirely new applications, which require 10,000 lumens or more, for example in area lighting.
Thermal management plays a central role in LED design. In this joint project, the PCB manufacturer Häusermann from Gars am Kamp in Lower Austria, with its HSMtec board technology makes possible thermal, high-current and 3D solutions with integrated copper elements in the form of wires or profiles on the basis of conventional FR4 printed circuit boards. To quickly dissipate the waste heat away from the attached LEDs to the standard heat sink attached to the bottom of the board, two 12 mm wide and 500 µm high copper profiles with a total length of 155 mm are used, which are integrated directly below the LEDs into the four-layer FR4-multilayer by means of ultrasonic bonding technology. As HSMtec enables self-supporting multidimensional PCB structures, each of the individual board segments can be placed in the desired mounting position and direction. This ensures a continuous metallic, thermal path from the hotspot of the laterally attached LEDs to the central heat sink even beyond the bend.
The PCB segments, individually formed to create an octagon, ensure photometric flexibility and interesting optical solutions. Narrow air slits on the sides enable the air to circulate, allowing operation without fans. PCB pin connections, which are fused on during the soldering process, are used for better stability and securing of the board segments to the bottom PCB.
“LEDagon demonstrates clearly that, thanks to HSMtec, both the LED and the required control electronics can be accommodated on one and the same PCB, and this with optimal thermal isolation”, explains Stefan Hörth, HSMtec Product Manager at Häusermann.
A total of 42 integrated wire connections with a diameter of 500 µm allow the connection of the multidimensional board segments for intelligent control of the individual LEDs. With HSMtec it is therefore possible to feed large quantities of heat and/or high currents of up to 500 A directly inside the PCB. Moreover, the entire construction requires no cable, plug or other mechanical connections. This not only improves the reliability of the application, but also its lifetime.
At the heart of the LEDagon is an 8-bit microcontroller from ATMEL, the Atmega328P. This high-performance, low-power microcontroller with advanced RISC architecture features 32 KByte FLASH, 2 KByte SRAM and 1 KByte EEPROM. In addition to the standard interfaces SPI, I²C and USART, further peripheral elements such as an 8-channel 10-bit AD converter and three timers with a total of six PWM channels are of importance for the LEDagon. The SPI interface is used as a debugging and programming interface for the integrated FLASH memory.
The supply voltage and ADXL213 tilt sensor from Analog Devices are measured via the 10-bit AD converter. This sensor is intended to show the control possibilities, which result from a tilt of the LEDagon in the X and Y direction. After being put into operation, the two angles of inclination X and Y are calibrated to zero.
Via the I²C bus the Atmega328P communicates with its remote peripheral, for example with a 10-bit temperature sensor and a capacitive touch sensor from SMSC, the CAP1114. The temperature sensor of the type LM75 rests directly on the central heat sink from Fischer Elektronik and monitors the maximum operating temperature of the LEDagon.
With the CAP1114 both capacitive buttons for mode selection and a 7-segment slider were implemented. With the slider, the user can manipulate analogue control variables such as the brightness and speed of the various demo programmes. Along with its capacitive touch functions, the CAP1114 also offers the possibility to control several low-power LEDs via open collector outputs. The LEDagon makes use of this possibility to confirm the capacitive buttons optically and represent the current operating mode in a 7-segment display. The I²C-compatible 2-wire interface used for this particularly suits the PCB design, since the main controller rests on the central surface of the LEDagon and the CAP1114 is located on the angled control panel.
The HSMtec PCB bending technique makes it possible to uncomplicatedly lead conductors via bent edges through integrated 500µm-thick wires. At any point on the multilayer, up to 9 connections are therefore available for the implementation of the LEDagon PCB design and corresponding component positioning.
A total of four PWM channels are required for the independent brightness control of the central LED Cree XLamp XM-L and the three times two LEDs Cree XLamp XPG on the lateral wings. For this, the Atmega328P provides two PWM channels with 16-bit resolution and four PWM channels each with 8-bit resolution. The central LED is operated with maximum 10W and controlled by the LM3423 National driver component. The six LEDs on the lateral wings are supplied with a constant current of about 500mA and split into three pairs each with two LEDs. Via a triple analogue switch, the three PWM control signals can also alternatively be diverted to the bottom level of the LEDagon by means of software, where they then control small red, green and blue LEDs for effective illumination of the interior.
“With the USB interface and a suitable host application, a myriad of possibilities open up, which go far beyond the local control functions. Thus the LEDagon with the Windows-based LEDagon Control Center, available on the KATHREIN-Austria homepage, is not only able to perform remote control and remote maintenance. It can also display all sensor values and load software updates”, says the technical manager of the “LED light & electronics” division at KATHREIN-Austria, Bernhard Kummer.
With LEDagon, companies are able to gain the opportunity to implement product ideas rapidly and economically with leading manufacturers who are able to offer a complete spectrum of technologies and services, ranging from design support through the integration of the latest technologies to assembly and component procurement.