GB2066543A - Test circuit for optical display devices - Google Patents

Abstract

Electric lamps 8 forming a group 4 are connected to a common test line 3, selected lamps being successively switched on and off by a lamp driver 6 in response to signals from a control unit 1, only one lamp being lit at any instant. The correct functioning of each selected lamp produces a corresponding pulse of a square wave signal from detector 2, e.g. a resistor, giving a square wave output on line 5 at the switching frequency. A missing pulse, detected as an increase in the time interval between two adjacent waves on line 5, causes the control unit to indicate failure. <IMAGE>

Description

SPECIFICATION Test circuit for optical display devices The present invention relates to a test circuit for optical display devices which are illuminated under supplied electrical power, the display devices being disposed in a group or groups wherein at most a single display device is illuminated within the or each group at any operating time.

Test circuits for optical display devices (for example filament lamps or fluorescent tubes which, for example, illuminate a plurality of lamp panels) are important whenever an observer is to be given results, or further processable conclusions through the optical indication of data or other random information contents. Data not available to the observer due to defective display devices are the equivalent to an omission of the necessary information or misinterpretations are possible due to the faulty display, which must necessarily lead to incorrect conclusions.

Equipment with optical data displays are, for example, slot machines or lotto number draw machines in which the lamp panels can be arranged in the form of concentric rings combined into lamp groups or in matrix form with groups arranged in rows and lines or in some other random form, such as a spiral or the like. In the case of such slot machines the failure of the data display corresponding to the failure of one or even more optical display devices or bingo winning row or 7-segment display devices, can lead to misinterpretations of the win obtained or the failure to win on the part of the player.

To obviate such problems it has already been proposed to couple each individual lamp with a control unit in such a way that in the case of a defect there is a remote indication indicating the defect to the machine operator. Thus, for example, it is known to carry out a lamp test through successively manually switching on and off all the lamps or similar optical indicating or display devices. However, this not only requires costly wiring to each individual incandescent lamp or bulb associated with a particular lamp panel, but also is a very time-consuming operation when there are numerous such lamp panels. In the known test circuits the remote indication is made possible by the fact that a test detector is provided for each lamp.That is, for example, constituted by a phototransistor in each lamp panel for each incandescent lamp, which necessarily not inconsiderably increases the cost of the complete test circuit. The aforementioned test circuit arrangement with a detector or current sensor for each optical display device can be replaced in the avoidance or at least the reduction of the risk of failure of lamps by associating with each lamp panel not one, but two or even more optical display devices, but this once again greatly increases the technical expenditure. The cost of such a solution is also scarcely reduced if the two incandescent lamps are replaced by a single lamp and emergency lighting associated therewith, e.g.

in the form of a light-emitting diode.

An object of the invention is to simplify a test circuit for optical display devices in such a way that the necessary circuitry is reduced, leading to a considerable drop in the hitherto unavoidable high costs for the test circuit.

According to the invention there is provided a test circuit for optical display devices which are illuminated under supplied electrical power, the display devices being disposed in a group or groups wherein at the most a single display device is illuminated within the or each group at any operating time, said test circuit comprising a single detector connected to each display device via a test line, said detector being associated with all the display devices within the or each group, and the detector being connected to a control unit for all the display devices by means of a test indicating line.

The optical display devices may be electric lamps of the incandescent filament or fluorescent tube type.

The large number of hitherto necessary detectors for the optical display devices or the fitting of second lamps for each lamp panel are now rendered superfluous and is replaced by a single detector for each lamp group. This solution for the first time utilizes the fact that in the case of equipment of the present type only one lamp or similar optical display or indicating device lights up at one time during the operation of the lamp group.The reduction in the number of detectors in the form of current sensors or the like to one for each lamp group also only makes it necessary to have one remote indication per group, it being unimportant whether the lamp panels are statistically selected optical display devices of a win means or a dynamically selected incandescent lamp or the like from a plurality of illuminations which, at elevated operating currents, are successively operated with a frequency above the manual perception limit in the so-called multiplex mode.

The invention will now be further described, by way of example, with reference to the accompanying drawings in which:~ Fig. 1 is a block circuit diagram of a test circuit formed according to the invention with a lamp group and a current sensor associated therewith via a common test line; Fig. 2 is a block circuit diagram of a modification of the arrangement in Fig. 1 using a decoder for data retransmission from the control unit; Fig. 3 is a block circuit diagram of a test circuit formed according to the invention combined with a matrix-like arrangement of optical display devices in a plurality of groups of the display devices; Fig. 4 is a modification of the arrangement in Fig. 3, using a decoder circuit;; Fig. 5 is a block circuit diagram of test circuits formed according to the invention each connected to a respective one of a plurality of groups of optical display devices, the detectors for respective groups being in parallel; Fig. 6 is a block circuit diagram of the arrangement in Fig. 5 modified to operate in multiplex mode with successive interrogation possibility, and Figs. 7 and 8 show diagrammatically embodiments for sensor circuits permitting indication in digital form of one or all the illuminating display devices within each lamp group.

According to Fig. 1 an embodiment of the test circuit for a group 4 comprising sixteen indicating or display devices 8 in the form of incandescent lamps, substantially comprises a per se known control unit 1 connected via sixteen control lines with a lamp driver operating as a current amplifier 6. Each of the sixteen drivers is connected by means of a line with the display or indicating device 8 associated therewith. A common connection for the detector 2 constructed as a current sensor leads from each display device 8 to a joint test line 3. When, for example, the detector is the form of an ohmic resistor, it is connected with one pole of the supply voltage U for all the optical display devices, i.e. in this case the lamp group 4.By means of the test indicating line 5 between detector 2 and control unit 1 the latter is supplied with a pulse sequence corresponding to the pulsed time selection of the individual display devices 8 within lamp group 4 in dynamic operation. The pulse frequency on line 5 which is repeated in cyclic manner during the test is only complete if each of the optical display devices 8 within the represented lamp group 4 is ready to operate, i.e. is not defective within the selection time associated therewith. The pulse sequence supplied by detector 2 control unit 1 lacks a pulse, as indicated in Fig. 1 by the square-wave pulses, if either the associated incandescent lamp should not light up or if it should light up but is defective, which is recognised by control unit 1 and is suitably indicated or recorded, e.g. by the automatic, stepwise switching on and off of the display devices.

In the embodiment of Fig. 2, as in Fig. 1 the optical display devices 8, which are e.g. combined once again into a single group 4 and are coupled via a single test line 3 to a detector 2, are directly selected by control unit 1. However, the difference compared with Fig. 1 is that between control unit 1 and lamp driver 6 there is a decoder 7, so that there can be a corresponding coded selection with four control lines and one release line between control unit 1 and decoder 7 and in general terms for 2n optical display devices with n control lines.

Figs. 3 and 4 show embodiments of the test circuits with matrix-like arrangement of the optical display devices, in which once again a lamp group 4 comprising 16 display devices is alternately connected by means of test lines with in each case two current amplifiers 6, 6' in the form shown in the block circuit diagrams.

In accordance with the embodiment of Fig. 2 the amplifiers are connected across decoders 7 and 7' to control unit 1 in the case of the embodiment of Fig. 4, whereas the embodiment of Fig. 3, like that of Fig. 1, is constructed without external decoders. This matrix-like arrangement further reduces the number of control lines and' once again a single detector in the form of a current sensor is associated with each lamp group.

Thus, the control unit is informed whether at a particular time the selected incandescent lamp or similar optical display device actually lights up or is defective, because in manner known per se, e.g.

using a microprocessor, the control unit is designed so that a given lamp or the address thereof is associated with each moment in time ensuring an easy fault indication if a lamp has failed.

In the embodiments of Figs. 5 and 6 in which several lamp groups 4 are associated with the test circuit, several detectors 2 are provided as a function of the number of lamp groups 4. As in the aforementioned embodiments these detectors are together connected to the lamp supply voltage U.

In parallel detectors 2 supply the state of the individual lamp groups 4 directly to control unit 1 in Fig. 5, or, as shown in Fig. 6, via a multiplexer 9 in successive interrogation.

In Fig. 7 control unit 1 constructed as a microprocessor is connected to current precision resistor 2' as the detector via a test indicating line 5 containing the transistor circuit shown in the circuit diagram. This embodiment applies once again to the test circuit with a current sensor in the case where only one lamp in a lamp group is selected or lights up at any operating time. If, as shown in Fig. 8, the current precision resistor 2' is coupled to an analog-digital converter 9, associated here with detector 2, it becomes possible with a single sensor to simultaneously test several lamp groups 4 with in each case one selected incandescent lamp or similar optical display device or several lamp groups with several simultaneously selected incandescent lamps, as can be advantageous, e.g. with a 7-segment display, The current sensor indicates to control unit 1 in digital form the sum of the illuminated, i.e. selected optical display devices. The control unit programme is such that it knows the sum of the lamps selected at any operating moment. The embodiment of the circuit according to Fig. 8, is, for example, suitable for a current sensor when simultaneously several optical display devices of a lamp group are selected.

Claims (5)

1. A test circuit for optical display devices which are illuminated under supplied electrical power, the display devices being disposed in a group or groups wherein at the most a single display device is illuminated within the or each group at any operating time, said test circuit comprising a single detector connected to each display device via a test line, said detector being associated with all the display devices within the or each group, and the detector being connected to a control unit for all the display devices by means of a test indicating line.

2. A test circuit according to claim 1 , wherein the or each detector is a current sensor.

3. A test circuit according to claims 1 and 2, wherein the detector is coupled to an analogdigital converter.

4. A test circuit according to any one preceding claim for optical display devices which are electric lamps.

5. A test circuit for optical display devices which are illuminated under supplied electrical power, the display devices being disposed in a group or groups wherein at most a single display device is illuminated within the or each group at any operating time, the arrangement being substantially as hereinbefore described with reference to Fig.1,2,3,4, 5,6, 7 or 8 of the accompanying drawings.