Modular programmable controlling system

Abstract

An indicating system has a left input section to which electrical leads from relatively high voltage apparatus in the field are coupled. The input section includes a number of horizontal input circuit boards which are electrically connected with a central 'logic' section having a number of horizontal logic subassemblies. Each subassembly comprises a 'daughter board' with subcircuits thereon which simulate the action of a number of sets of relay switch contacts and the action of a coil which 'controls' the respective states of certain ones of the sets of contacts. The central logic section is connected to a right output section comprising a number of vertically-spaced, horizontal output circuit boards which isolate the logic section from the voltages in the valves, motors, etc. in the field that are controlled thereby. A plurality of modules are provided which may be manually slipped onto the front edge of the 'daughter board', each module bearing a symbol representing a component of a conventional ladder diagram. When it is pressed inward onto the front edge of the daughter board, it may have a portion which cooperates with one or more of the logic subcircuits thereupon, causing that subcircuit to simulate the operation corresponding to the symbol on the module. The module symbols and vertical lines on the left and right sections create a conventional ladder diagram whose operation is electrically simulated by the central logic section's subcircuits.