The present invention relates to LED bar modules (2) where the LED groups are placed at a pixel board (6). 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 (4), where the pixel board (6) is placed outside the heat conductive tube (4) in a longitudinal recess, where the main printed circuit is placed inside an isolation cover (12). Hereby, it is achieved that the LEDs are placed on the outside of the tube (4) in a way where heat generated from the LEDs is conducted downwards to the tube (4). Inside the tube (4), the rest of the power electronics and also the light controlling electronics are placed.