The present invention relates to LED bar modules where the LED groups are placed at a pixel board. The present invention further concerns a method for calibration of LEDs. It is the object of the invention to achieve a highly efficient LED bar for generating a bar of light. A further object of the invention is to store calibration data for each LED both electrically and mechanically close to the actual LED. Preferably, the main printed circuit is placed inside a heat conductive tube, where the pixel board is placed outside the heat conductive tube in a longitudinal recess, where the main printed circuit is placed inside an isolation cover. Hereby, it is achieved that the LEDs are placed on the outside of the tube in a way where heat generated from the LEDs is conducted downwards to the tube. Inside the tube, the rest of the power electronics and also the light controlling electronics are placed.