Patent GB-1339028-A (GB)
Title: Digital computer-industrial controller system and apparatus
IPC: G05B15/02
Filed: 1970-12-11
Abstract: 1339028 Data processing systems MODICON CORP 11 Dec 1970 [11 Dec 1969] 59171/70 Heading G4A [Also in Division G3] A process is controlled in response to a simulated ladder type control circuit stored by a digital computer carrying out an executive programme which interrogates a programming panel on which the elements of a line of the circuit are manually specified. As shown, Fig. 1, a small general purpose computer 32 is connectable to a programming console 34 by a detachable lead 36. The computer services external registers and signal conditioning circuits, forming part of a process to be controlled, mounted in a box 40 through a cable 42. Input signals to the box 40 are provided on terminals 44 from devices such as a pushbutton 50, limit-switch 52, pressure switch 54 and relay contacts 56. Output signals are provided on terminals 46 to controlled devices such as a relay 58, a lamp 60, a motor 62 and an alarm 64. The computer carries out an executive programme, whereby a simulated relay logic ladder network is stored as a control programme for the process, in response to line-by-line series logic manual programming by actuation of the console 34. A line number is set by thumb-wheels 68 and a function, selected by a thumb-wheel 70, is positioned in a line by a latching pushbutton 74 which lights up. The line number of a relay governing the condition of the selected element is set by thumb-wheels 72. The element is entered into the simulated network by depression of a push-button 76 and indicated on a display 80. The status of the relay of the line selected by thumb-wheels 68 is indicated by a lamp, not shown. The ladder network, Figs. 4A, 4B, simulated in the memory of the computer by use of the console 34 as interrogated by the executive programme, comprises lines L1, L2 between which are connected lines of group 115 controlling output devices 58-64 through relays 116 and signal conditioning circuitry 92. The elements in a line comprise open or closed relay contacts 126, 128 a branch circuit 130, influenced by contacts in another line, and a link 132. Additionally, timers and counters, not shown, can be included in a line. A group of lines 122 is controlled by external devices 50-56 and a further group of lines 124 is set up for internal control only. Facilities are provided for recording a prepared control programme and remote servicing of the computer control system through a telephone link from a central small general purpose computer associated with a teletypewriter and paper tape reader and punch. The executive programme examines each line of the element-equivalent logic stored in a core memory of the computer, and updates the condition of the simulated elements and effects a control function on the process being controlled in dependence on the status of the relay in a line. The programme (a) scans the input terminals which are connected to devices responsive to the conditions of the process and (b) scans the status of the programming panel to determine whether the user desires to change or add to the simulated elements in a circuit line stored in logic form.