GB2111783A - Electronic control device using optical links - Google Patents

Abstract

A control device has a central unit (1) for processing signals, and plug-in interface units (6) for the transmission of monitoring signals to the central unit and for the reception of control signals from said central unit. The central unit and the interface units are electrically insulated from each other, the transmission of signals therebetween being purely optical, by means of photo transistors (11) and light-emitting diodes (12). These light-electrical transducers are attached to printed circuit boards (13) which comprise the interface units, and to a printed circuit board (4) which acts as a distributor bus of the central unit. <IMAGE>

Description

SPECIFICATION Electronic control device It is well known to use electrical control devices which are divided into several separate plug-in units.

A popular embodiment of such a device consists of a central unit having a number of electrical terminals for the input of monitoring signals and for the output of control signals, respectively, and of a plurality of input and output units which deliver monitor signals to the central unit and receive control signals from the same, respectively. This arrangement allows to use input and/or output units which are specialized for particular tasks and can be exchanged as necessary, which has proved useful in industrial applications. In order to economise space, the electrical connections generally are distributed along a bundle of bus bars, or along a ribbon cable with multiple wires, which ends in the central unit and transmits signals in both directions. As a rule the necessary currentforfeeding the input and output units is also provided through this bus.

The drawback of such known embodiments mainly lies in the low reliability of the electromechanical connections at the junction between the central unit and the input and output units, respectively, and also at the junction between the cable or the bus and the central unit. This entails a secondary drawback, i.e.

the necessity to check these junctions together with the control device as a whole, which means that it is not sufficient to check the central unit and the input or output units severally, especially because faulty contacts at the junctions represent one of the most frequent malfunctions and often only arises when the final setup is plugged together.

Furthermore, many control problems require that the electrical potentials of the controlled apparatus and of the central unit be independent, so that an opto-insulation must be inserted into the signal path.

This leads to additional costs which increase the already high expenses for building reliable electromechanical plugs, when the security requirements are stringent.

The invention aims at avoiding these drawbacks and at creating a control device of the aforementioned kind, the separate units of which can be checked severally without incurring any noticeable risk that additional sources of failure will arise when individual input or output units are plugged in or exchanged. Furthermore, the invention aims at providing good electrical insulation between said units and the central unit, and the construction of the device shall be suited to the use of printed plates, because these can easily be manufactured automatically.

To this end the device according to the invention is defined as stated in claim 1.

In what follows the invention shall be further illustrated at hand of embodiments of the same, and with the help of the drawing wherein: Figure 1 shows a schematical section through an embodiment of the invention, Figure 2 shows a schematical plan view of the same, and Figure 3 shows a junction between the central unit and an interface unit plugged into its bus extension.

Figure 1 shows a schematical section through an embodiment of the invention. Numeral 1 indicates the housing of a central unit, within which there is placed a printed plate 2 for the feeding circuits, and printed plate 3 for the logical circuits. A further printed plate 4 protrudes into an elongated appendix 5 of the housing, which comprises the necessary (but not shown) fixtures and, if needed, catches for coupling on input units, output units, or combined input-output units (of which only one is indicated and identified by the numeral 6). In what follows such units will be generally called interference units.

The distributing printed plate 4 mainly serves as a bus for electrical signals moving in both directions between the central control unit and the junctions, indicated by the numerals 7, 8, 9 (Figures 1 and 2), where the interface units are to be connected. The junctions are realized by mechanically separable opto-couplers. For each individual signal path the distributing printed plate 4 carries either a photo transistor 11,for signals traveling in direction of the central unit, or an LED-diode 12, for outwards traveling control signals. In a complementary fashion the interface units contain either LED-diodes, in the first case, or photo transistors, in the second case, as sketched in 14 (Figure 1), and as can also be inferred from Figure 3.This Figure illustrates a detail of a simple implementation of the housings 5 of the central unit, and an interface unit 6, respectively. At the junction each housing has an opening 21, 22 for the passage of light. In this region the housing of the interface unit has a protuberance, and the housing of the central unit a corresponding hollow, which together form a kind of plug-in connection which guarantees at the same time a mechanical centering of both openings and a sufficient protection from external light sources.

Figure 2 shows different kind of connections on the central unit, one numbered 7 for input units, one numbered 8 for output units, and further numbered 9 for interface units which work in both modes. The first kind of connections 7 comprise only photo transistors (which are symbolized by points), the second kind 8 exhibits only photo diodes (symbolized by crosses), and the last kind 9 comprises both kinds of light-electrical transducers. The transducers 11, 12 which belong to the central unit, as well as the transducers 14 which belong to the interface units will preferably be located directly on a printed plate that belongs to the corresponding unit; the transducers of the central unit will in particular mostly be fixed directly on the bus-like distributor plate 4.The print plates can be manufactured automatically, and all units can be checked separately because no additional sources for malfunctions are introduced when the units are plugged together, even if this is done without particular care. Moreover the central unit can be constructed always in the same fashion, independently of the interface units which will be plugged on. At the same time it is easy to obtain an excellent electrical insulation which will allow up to 4 KV difference of electrical potential between the central unit and the interference units. The latter may be, e.g. affixed to the central unit with snap-on connections.

Because no electrical energy is transferred from the central unit to the interface units, the latter must obtain feeding current from the circuits which are to be controlled. However, this entails no additional difficulty, because the necessary amount of current remains unnoticeably small for the controlled circuit and can thus be drawn from the lattertogetherwith the monitoring signals. It must be noted, that current will always be available, as long as there is anything to control.

In the lower part of Figure 2, chained lines indicate how a further central unit module 10 can be connected to the central unit through a lateral connecting plug 15, which can of course be provided either on one or on both sides of the corresponding unit.

Claims (7)

1. Electrical control device, with a central unit and at least one satellite interface unit connectable to it for inputting monitoring signals into the control unit and/or for receiving control signals therefrom, where the central unit processes the inputted monitoring signals with stored informations and if necessary also with timing signals in order to control the interface unit, characterized in that the electrical circuits of the central unit on one hand and those of the interface unit on the other hand are electrically insulated from each other, and that the signal pathways between interface units which are physically connected to the central unit in a mechanically releasable way, and the central unit are exclusively optical pathways.

2. Control device accorfding to claim 1, characterized by at least one interface unit for inputting monitoring signals into the central unit, which interface unit has ports provided for connection with the central unit and comprising light-emitting elements, whilst the corresponding ports of the central unit exhibit light-sensing elements.

3. Control device according to any of the preceding claims, characterized by at least one interface unit for the reception of control signals from the control unit, which interface unit has ports provided for connection with the central unit and comprising light-sensing elements, whilst the corresponding ports of the central unit exhibit light-emitting elements.

4. Control device according to claim 2 or 3, characterized in that the light-emitting and/or lightsensing elements of the central unit are located on a printed circuit plate which acts as a distribution bus.

5. Control device according to claim 4, characterized in that the central unit possesses several printed plates acting as distribution busses, which are daisy-chained by way of electrical plugging means.

6. Control device according to any preceding claim, characterized in that, on the sending and on the receiving side the light-emitting and lightsensing elements both are light-electrical transducers located proximate to the surface which separates the central unit from the interface units.

7. An electrical control device substantially as hereinbefore described with reference to and as shown in the accompanying drawings.