Open board PLCs are integrated into a machine or device's own enclosure to handle sequencing, timing, counting and input/output control. This category covers programmable boards for different control requirements, including the DERELL DLB series. The protective enclosure, mounting arrangement and wiring must be designed to suit the machine.

Relay-output models are considered for general on/off switching within their contact voltage and current ratings. Transistor-output models are used for fast switching of suitable DC loads; pulse control also requires specifically designated high-speed outputs. Analog I/O, high-speed counters and pulse outputs are not included on every board; check the channel counts and speed limits for each model.

When selecting a board, consider supply voltage, digital I/O count and type, output current, analog signal ranges and board dimensions together. The supported ladder programming software, programming cable and connection port must be compatible. For an HMI panel, check port, protocol and communication settings compatibility; confirm RS485 and Modbus support in the product's technical documentation.