COol COntroller COncept For many devices one or two buttons suffice for their control. With this in mind we designed a hexagonal little board, several of which can easily be fitted behind the front plate of a DIY project. A rotary encoder or pushbutton serves as a control, with a ring of 16 two-color LEDs indicating the value or position. Display Board for VariLab 402 A display board provides simple and straightforward operation of the VariLab 402 PSU described in this issue. On a 4-line LCD various measured and calculated values are shown, the operation being done with two rotary encoders and a pushbutton. The circuit is designed such that it’s easily dropped into other measurement and control circuits. Programmable Christmas Tree No December edition of Elektor is complete without a Christmas Tree project. This year, in cooperation with Eurocircuits we developed a Christmas tree with 62 LEDs in a matrix encapsulated in PCB material. The flexible tree is special in being customer programmable, meaning you design your own light effects and patterns. Connect the tree to your PC and enter the LED patterns in a browser by mouse clicks.