PDP-14 Programmable Controller Product Summary

The PDP-14 Programmable Controller, developed by Digital Equipment Corporation, is a solid-state system designed for repetitive manufacturing and process control. It serves as a direct replacement for conventional relay-based systems, accepting two-state inputs (e.g., limit switches, push buttons) and controlling two-state outputs (e.g., solenoids, motor starters) based on a user-defined control sequence stored in its easily alterable memory.

The system is composed of a Control Unit, Input (I) boxes, Output (O) boxes, and Accessory (A) boxes. I-boxes convert 115 VAC or DC signals from sensing devices into low-voltage signals for the control unit, while O-boxes switch 115 VAC or DC power to controlled devices. Both I/O boxes feature indicator lamps for troubleshooting and provide electrical isolation. Accessory boxes offer functions like timers, retentive memories (retaining data upon power loss), and temporary storage.

The Control Unit executes basic operations: testing input/output states, determining control functions, and setting outputs. It uses either a permanent Read Only Memory (ROM) with wired instructions or a flexible 4,000-word Read/Write Memory (MM14-A) that allows for easy program alteration. Program development tools like CRT-14 (for ladder diagrams) or SET-14/BOOL-14/SIM-14 (for Boolean equations) run on PDP-8 family computers, enabling control engineers to create, debug, and load programs without extensive computer programming.

The PDP-14 can function independently or be monitored and controlled by a general-purpose computer (e.g., PDP-8 or PDP-11) for status reports, malfunction reports, or command override. The system is designed for user maintenance, utilizing indicator lamps on I/O boxes and an interrogator box (BT14-A) to diagnose faults in either the controller or external field devices. Hardware specifications include support for up to 256 inputs and 255 outputs, operating on standard 115 VAC or various DC levels, within a 0° to 70°C ambient temperature range, and meeting J.I.C. Electrical Standards. The control program scans at approximately 15 milliseconds per 1K of memory.