CIRCUIT BOARD INPUT RACK ASSEMBLY

Abstract: A circuit board (1) for a programmable controller has a number of plug-in input modules (11) which may be of widely varying type. The board of the invention allows the input signals to be matched to the modules by providing a voltage controlling circuit (40) between each input module station and its associated input terminals (12) on the board. Each voltage controlling circuit comprises potentiometer means (41, 42) and filter means (43).

Description: BO RD FOR INPUT RACK ASSEMBLY This invention relates τo a circuit board for an input rack assembly of a programmable controller of the type employing input modules. . • ' In this type of programmable controller the processor 5 receives input data from the system being controlled via a plurality of input modules arranged on an input rack assembly. . The modules are adapted to receive input data from the system indicating the status of the various i elements of the system and produce from this data logic 10 signals which are then passed to the processor. The modules also serve to indicate the status of the associated element and to suppress noise. The input status signals from the system, i.e. inputs from push buttons, limit switches, selector 15 switches, pressure switches, etc. may be of different voltage levels and may be either d.c. or a.c. Therefore, the input status signals in a single system may comprise signals having different voltage levels and in such cases it is necessary to identify the voltage level of the 20 signal in a particular channel and provide for that channel an input module which is capable of receiving β * a signal of that level and produce therefrom the required logic signal. Thus, hitherto, it has been necessary to provide a* 25 range of input modules capable of handling the different input status signal voltage levels in a given system. It is an object of the present invention to provide a circuit board for an input rack assembly which does away with the need to provide a range of input modules capable of handling various voltage levels of different types of input signals. According to the present invention there is provid a circuit board for an input rack assembly of a programmable controller of the type employing input modules, the board including a plurality of input terminals for receiving status input signals from the system being controlled, and a plurality of socket ! stations for receiving plug-in input modules, each sock being connected to associated input terminals through a respective voltage controlling circuit, said circuits including selectably adjustable filter means and select adjustable potentiometer means, whereby the status inpu signals passed to individual sockets may be of the desi voltage type and voltage level. An embodiment of the present invention will now be described, by way of example, with reference to the accompanying drawings, in which: Fig. 1 is a plan view of one embodiment of a circu board for an input rack assembly according to the prese invention, and Fig. 2 is an electrical circuit diagram of the cir board of Fig. 1. Referring to the drawings a circuit board for an input rack assembly or a programmable .controller compr OMP >, IP a base 1 having a plurality.of pairs of socket mouldings 11 fitted thereon. Each pair of socket mouldings 11 forms a socket adapted to receive plug-in input modules of the type, for example, described in U.K. Patent Specification No. 1453195 (GB-291) . Each socket 11 is provided with terminals which contact pins of the plug-in input module. Socket output terminals connect the plug-in input_ module to addressing integrated - : circuits 3 to 8 and serve to f;eed logic signals from the module to the processor. The circuit board is provided with input terminals 12 for receiving status input signals from the system being controlled. To ensure reliable' operation of the elements of the system the status input signals are generally of- a particular level depending on the element and the input signals may vary from a low level d.c. signal to a relatively high level a.c. signal. Since the circuit board of this invention has been designed for use with one type of input ' plug-in module it is necessary to ensure that the input status signal which is passed to the input module is of a level and of a type which the module can handle to produce from this input status signal the necessary logic output for the processor. To this end the input status signals are passed from t h e input terminals 12 to socket input terminals through voltage controlling circuits 40. Each voltage controlling circuits 40 includes a OMPI ° selectably adjustable potentiometer made up of a group of resistors 41 and selector switch 42. The adjustable potentiometer allows the input signal to be brought to a level which can be handled by the input module. Each voltage controlling circuit 40 also includes an adjustable filter 43. The filter 43 is suitably, a switched RC filter with a maximum time constant of about 15 ms. When the module is used with an a.c. ;- input, the filter 43 can be used to filter noise from the rectified input. "With a d.c. input, the filter can be used to introduce a desired delay to input signals. The output of the voltage controlling circuits 40 are passed to respective socket input terminals which contact the input pins of the plug-in in-put modules. Referring to Fig. 2, eight channels of the circuit board are shown. The gates 44 are formed by the i.c.'s 5 through 8 of Fig. 1, while ICl and IC2 of Fig. 2 correspo to the items 3 and 4 respectively of Fig. 1. The logic output signals from the socket output terminals are passed to a connector plug 50 which may be of the type to receive the I/O data cable terminal described in our co-pending U.K. Application No. 32889/78 (Case 3) . The physical dimensions of the circuit board are such to allow the board to be used with the rack assembly of our co-pending ^ Application No. 32892/78 (Case 1) . Thus, the circuit board of this invention allows a single input module to be used even when the input status signals from the system being controlled are of widely differing voltage levels and response times. This obviates the need for a user to have at his disposal a number of different input modules which would cover the range of voltages received from the system.

Claims: CLAIMS . 1. A circuit board for an input rack assembly of a programmable controller, the board including a plurality of input terminals for receiving status input signals from the system being controlled, and a plurality of socket stations for receiving plug-in input modules, each socket station being connected to associated ones of the input terminals through a respective voltage controlling circuit, each voltage controlling circuit including selectably adjustable filter means and selectably adjustable potentiometer means, whereby status input signals passed to individual socket stations may be of desired voltage types and voltage levels. 2. The circuit board of claim 1, in which each potentiomenter means comprises a plurality of fixed resistors and switch means to connect selected ones of the resistors in circuit. OMPI WIPO

Inventors: CLARKE G
Applicants: CLARKE G, SQUARE D CO
Application year: 1979
Main classification: H05K3
IPC codes: G05B19, G06F1, G06F3, H05K1, H05K7