N-400 Keyence Multi-Drop Controller for BL Series Bar Code Readers

The Keyence N-400 Multi-Drop Controller for BL Series can control up to thirty-one BL series units using a host computer, enabling the multi-drop link configuration. The communication path is an RS-485 cable, which provides high noise-resistance and enables data transmission over a long distance (up to 1.2 km). Since a twisted pair cable (two cables) is used for the connections, the multi-drop link configuration can be realized with simple wiring.

The N-400 controls the complicated communication (RS-485 communication) between each BL series and the N-400. Since the host computer works only for communication with the N-400, it can be operated with a simple program. (The ID number assigned to the head of the transmitted data allows you to identify the BL series unit that sends the data.) Therefore, the host computer's job is reduced with this system configuration.

If the position of bar codes is unknown in a product, or bar codes are printed in several positions, the bar codes cannot be read with a single bar code reader. In such cases, several bar code readers need to be mounted in various positions or at various angles. When the N-400 controller is used in multi-head scan mode, a host computer can control several BL series units as if they were a single unit.

When several bar code readers are mounted close to each other, for example when reading multi-stage labels, the units' light sources (laser beams) interfere with each other, affecting the reading stability. The mutual-interference suppression function allows the BL series' laser beams to turn ON sequentially, thus suppressing the mutual interference to ensure stable readings. Since the laser beams turn ON sequentially, the duration of laser OFF time (when each unit is not reading a bar code) becomes longer as the number of connected units is increased. Therefore, the bar code readers may fail to read bar codes if the line speed is set too fast.