GB2041592A - Electrical control system - Google Patents

Abstract

In an electrical control system of the time division multiplex type, especially for use in automobiles, the transmitting and receiving positions are interconnected by a closed-loop signal highway. The equipment at the above- mentioned positions consists of standard modules each of which is settable for use as a transmitter or a receiver. Thus in a car the dashboard has one or more transmitting modules for sending out signals to control the various functions such as the car's lamps and its horn, there being receiving modules at the remote points for those signals. In addition the dashboard has one or more receiving modules which receive signals including check signals to indicate the condition of controlled devices, plus analogue signals for meter readings. <IMAGE>

Description

SPECIFICATION Electrical control system This invention relates to time division multiplex (TDM) communication systems for remote control and telemetry. Although not so limited, the invention is described herein as applied in motor vehicles.

The conventional method for controlling the various services in a motor vehicle, e.g. lights, windscreen wipers, etc. is for each one to be separately controlled from the dashboard, and for separate connections to be made from each monitoring or sensing device to indicator at the dashboard. This leads to complex and expensive wiring harnesses, so efforts have been made to produce control systems based on TDM principles. One example of such a system is described in our Patent Specification No. 1,476,805 (A.E. Brewster et al 73-52-13-9-1), and this invention seeks to provide a system using the same principle as does the above-mentioned Patent, but which is simpler and cheaper.

According to the invention there is provided an electrical control or indicating system, which includes one or more transmitting means connected via a signal path to a number of receiving means, each said receiving means being associated with a device to be controlled, wherein each said device is allocated a time position in a repetitive cycle of time positions at each of which a signal may be sent in respect of that one of the devices, wherein the nature of each said signal depends on the influence to be exerted on its one of said devices, wherein each said receiving means is responsive only to a signal at the time position or one of the time positionsappropri- ate to a device to be controlled via that receiving means, wherein the detection of a said signal at a said receiving means causes the appropriate control to be exerted on the device to which that signal corresponds, wherein each said receiving means consists of a standard modular unit which function for the transmission or the reception of signals at one or of said time positions, each such unit which functions as a receiver being adapted to receive and respond to signals at its one or more time positions, and wherein said transmitting means consists of said modular unit which functions to transmit control signals at one or more of said time positions.

According to another aspect of the invention there is provided an electrical control system for controlling a number of devices from a central point, which includes transmitting means at the central point connected via a single signal path to a number of remote points at each of which a receiving means is located, such said recovery means being associated w::+h one or more of the devices to be controlled wherein each said device is allocated a time position in ) repetitive cycle of time positions at each of which a control signal may be sent in respect of that cre of the devices, wherein each said control signal is a 1 or 0 signal dependent on which of its two nditions the controlled device is to be set to, wherein each said receiving means is responsive only to a signal at the time position or one of the time positions appropriate to a device controlled thereby, wherein the detection of a said control signal at one of said receiving means causes the appropriate control to be exerted on the device to which that control signal corresponds wherein each of the receiving means consists of a standard modular unit which can function either for the reception or the transmission of control signals, each said modular unit functioning as a receiving means being adapted to receive and respond to said control signals, and wherein the control equipment at the central point consists at least one of said modules which functions, in response to control inputs to transmit control signals in the division multiplex manner over said signal path.

An important distinction between the above system and that of our earlier Patent is that we now have single type of module which is usable either as a transmitting device or as a receiving device.

T us the central point equipment, usually located at the dashboard consists of one or more modules which act as transmitters for sending signals to control the various devices to be controlled, and one or more modules which act as receiver for meter and other indications. The "remote" modules correspondingly include receiver modules, which respond to the control signals, and transmitter modules which send various indications including meter readings to the central point.

This use of a single type of module leads to a useful economy due to the reduction of the number of types of devices needed.

An embodiment of the invention will now be described with reference to the accompanying drawings, in which: Figure lisa simplified block schematic of a TDM system for automobile use which embodies the present invention.

Figure 2 is a simplified schematic of a module such as used in Figure 1 when functioning as a receiver unit.

Figure 3 shows part of the controlling pulse cycle used for the system.

Figure 4 shows various aspects of the equipment pracice used in the system of Figures 1 and 2.

In Figure 1, the central point equipment at the dashboard, includes modules 1,2, of which module lisa transmitter which emits control signals over a signal highway interconnecting all units of the system in closed-loop manner. Module 2 acts as a receiver for meter-reading signals. There is also a number, twelve as shown, of "remote" r-,sdules, some of which act as receivers for control signals while others act as transmitters for meter-reading and other indicating signals.

Power for the system comes from a battery 4 shows positive terminal is connected to a power bus supplying all modules of the system, the negative side of the battery being earthed. The signal highway and the power bus are represented in Figure 1 by a single line 5, but in the present system they are separate conductors.

Control for the system is based on a clock pulse source, which is combined with a digital clock on the dashboard, as indicated at 6.

We now digress to Figure 3, which shown the portion of the timed pulse cycle from the clock for one module. This starts with a synchronising pulse of amplitude D, A being the "off" condition, followed by three clock pulses of amplitude C to define the "time slots" within a module's portion of the cycle.

Each clock pulse and the sync pulse is followed by an "off" condition of amplitude A or an "on" condition of amplitude B. Note the dual use of the sync pulse: if desired, the sync-pulse and clock pulse functions could be separated.

The complete cycle consists of a pulse combination such as shown in Figure 3 for each module, possibly with a few spare time slots to allow the addition of functions to the system. In addition an additional sync pulse, distinguishable from the clock and sync. pulses, could be provided to define the commencement of the system cycle, but this is not shown as it can follow conventional practice.

Each of the switches at the central point, assumed to be the dashboard of a motor vehicle, when operated selects the time position for the device to which that switch relates, using conventional electronic circuitry. The selected time position is then followed by an "off" or an "on" condition, depending on the condition to which the device is to be set.

At a receiver module for each of its functions there is electronic circuitry responsive to its time position in the cycle, and this detects the incoming signals and passes the result on to the controlled device, or to an indicator in the case of a returned motor reading. In the case of meter reading signals, the amplitude of the signal following the sync. or clock pulse is proportional to the meter reading to be sent, i.e. it is an analogue signal.

Of the modules shown, modules 1 and 2 at the dashboard have already been described. Module 7, which is under the bonnet of the car, is a transmitting module. Its upper two inputs are variable resistors whose values are set in accordance with the oil pressure and temperature, so that they "modulate" the module's time slots in accordance with the values of the parameters to be signalled.

The other two switches are closed respectively when the reversing light and the brake light are to be lit at the dashboard.

On module 1, contacts H are for hazard lights, R and L for right and left-hand indicator lights, Hn is for the horn and ST for the side/tail lamp. Module 2 controls, in response to received analog signals, the oil pressure gauge and the water temperature gauge.

The other modules are receiving modules for various controlled devices such as lights and the horn.

As an example, if the horn switch Hn, connected to one input of module 1 is closed, the module awaits the horn's time position and when that occurs sets that time position to its "on" condition. At the appropriate receiving module 8, the newly "modulated" time slot is detected in the module 8, and the detection of this "on" condition operates the horn v !. The other two outputs from module 8 are the right-hand indicator and one of the side lights.

To overcome the risk of incorrect operation due to noise it is possible, as in our above-mentioned Patent Specification No. 1,467,805, to provide that a control signal is only responded to when it has been correctly detected on two successive cycles of the system.

Figure 2 shows a transmitting module, and it includes a block 10 which represents a special integrated circuit which provides the main part of the modules used in the present system. From the above description, much of the functions of the circuit will be clear, and much of the circuit techniques used can be on the same basis as the corresponding circuitry of the above-mentioned Patent Specification. This module is connected to the power bus 11 and the signal line 12, and it has pair outputs 13, one per function to be trasmitted, two of which are on/off conditions while the other two are analog functions.

Allocation of the various time slots to the functions uses a set of four output leads 14, which, like the leads 13, go via a connector 15 to a flexable printed circuit 16. This latter provides the connection to the devices whose conditions are to be signalled.

As the module is a transmitting module its power connection 17 is connected on the flexible circuit.

The other two connections are another power connection 18 and the system's earth connection 19. In the case of a receiving module, the connections 17 is not connectable.

The flexible circuit 16 is on a base plate 20 for plugging in to the connector 15, and the address connections 14 are connected to ground according to the address required.

Thus it will be seen that all input signals, whether analog or digital, are fed into the "universal" modules, each of which is a pure input device, i.e. a transmitter, if the input conversation pin is connected to power, as in Figure 2. If it is an "output" device, i.e. a receiver, this pin is not connected to power. Further, there are two forms of flexible circuit arrangement used for the receiver modules. In the low power module, the connections on the flexible circuit are as shown in Figure 2, except that the power connection 18 is not connected to the output.

For the higher powers module the connections 13, each of which is now an output, are each provided with a simple transistor chip which acts as a power amplifier.

The integrated circuit unit includes threshold circuitry, to deal with the multi-lead signalling techniques used, and is so arranged that any signal below 3 volts is ignored to provide noise immunity.

A signal at 9 volts is considered as "on" for a digital input or fully on for an analog input. Additional voltage over 9 volts and up to 12 volts (the usual car battery voltage) has no effect, this tolerance allowing for contact resistance on input switches.

Figure 4 shows the equipment practice features of the modules used in the system described above.

The central item of each module is a centre block 25 which is a plastics encapsulation of the integrated circuit unit 10, Figure 2. This block has transverse grooves 26 at its ends for automatic assembly tools, and longitudinal grooves 28, 29 along its top for the twin cable 30, which forms the power bus and signal highway. The upper surface also has insulation displacement connectors 31,32 for rupturing insula- tion to establish contact to the twin cable 30. The upper section 33 has grooves for receiving the twin cable and transverse slots such as 54 to receive the spikes which form the insulation displacement connectors 31, 32. In addition the block 25 has three upstanding tongues such as 34 for reception in slots such as 35 in the upper section 33.

The module also has a base member 36 which has a metallic insert 37 which provides an earth connectionwhen the base member is mounted, e.g. by screws to the car body. This base member carries a number of transistor chips 38 potted in epoxy. It also has insulation displacement connectors such as 39.

In use, a flexible circuit such as shown at 40 is placed on the base member 36, which is then mounted on the block 25. The block 25 has slots to receive the connetor spikes such as 39, and there is a hump 41 to provide strain relief for the flexible circuit. To assemble a module, the base member 36 is placed on the block 25 with a flexible cable 40 between them, and thus the upper section 33 fitted on over the two busses 30. The whole is then held together by a spring clip 42.

In a system in which the transistor circuitry is all in the block 25, the chips such as 38 on the base member are not provided.

Claims (7)

1. An electrical control or indicating system which includes one or more transmitting means connected via a signal path to a number of receiving means, each said receiving means being associated with a device to be controlled, wherein each said device is allocated a time position in a repetitive cycle of time positions at each of which a signal may be sent in respect of that one of the devices, wherein the nature of each said signal depends on the influence to be exerted on its one of said devices, wherein each said receiving means is responsive only to a signal at the time position or one of the time positions appropriate to a device to be controlled via that receiving means, wherein the detection of a said signal at a said receiving means causes the appropriate control to be exerted on the device to which that signal corresponds, wherein each said receiving means consists of a standard modular unit which functions for the transmission or the reception of signals at one or more of said time positions, each such unit which functions as a receiver being adapted to receive and respond to signals at its one or more time positions, and wherein each said transmitting means consists of a said modular unit which functions to transmit control signals at one or more of said time positions.

2. An electrical control system for controlling a number of devices from a central point, which includes transmitting means at the central point connected via a single signal path to a number of remote points at each of which a receiving means is located, each said recovery means being associated with one or more of the devices to be controlled wherein each said device is allocated a time position in a repetitive cycle of time positions at each of which a control signal may be sent in respect of that one of the devices, wherein each said control signal is a 1 or 0 signal dependent on which of its two conditions the controlled device is to be set to, wherein each said receiving means is responsive only to a signal at the time position or one of the time positions appropriate to a device controlled thereby, wherein the detection of a said control signal at one of said receiving means causes the appropriate control to be exerted on the device to which that control signal corresponds wherein each of the receiving means consists of a standard modular unit which can function either for the reception or the transmission of control signals, each said modular unit functioning as a recovery means being adapted to receive and respond to said control signals, and wherein the control equipment at the central point consists of at least one of said modules which functions, in response to control inputs to transmit control signals in time division multiplex manner over said signal path.

3. A system as claimed in claim 2, wherein the central point includes one or more receiving modular units for the reception of indicating signals from remote points at which one or more transmitting modules exist.

4. A system as claimed in claim 3, wherein at least one of the transmitting modular unit sends analog signals for at least one of its devices, the corresponding receiving modular unit controlling one or more meters.

5. A system as claimed in claim 1, 2,3 or 4, wherein the signal path is a single signal path connected to all receiving and transmitting means in closed-loop manner.

6. A system as claimed in any one of the preceding claims and wherein power supply is conveyed by a separate power bus which parallels the signal path.

7. An electrical control system for automobile use, substantially as described with reference to the accompanying drawings.