Electronic Digital Clocks

This invention relates to an electronic digital clock having at least one time-programmed electrical output for triggering switching functions.

Electronic clocks providing a digital display are known, in which a constant-frequency signal is applied to a clock circuit. The constant-frequency signal can be generated by a crystal or can be derived from the electrical mains supply. The clock circuit generates coded signals, usually BCD signals, which are applied to a display logic circuit. The display logic circuit in turn drives for example a seven segment display. The switching sequence of the coded signals and the display logic circuit is determined by a multiplexer which is supplied with pulses from the clock circuit. In this fashion, it is possible to provide an opto-electronic digital time display, which may for example include a display of the day of the week.

Time switches are known which have a time-programmed electrical output in order to trigger switching functions. The time-programming is performed mechanically by a timer disc which at a preset time, which is determined mechanically, closes or opens switching contacts. In electronic digital equipment such an arrangement is not possible because no mechanical moving parts are present.

In electronic digital clocks it is, however, known to provide a time switching function. For this purpose, an electronic store is provided and, when the stored value corresponds with the time displayed by the clock, a signal triggering a switching function is generated. The store can consist of a decade counter pulsed by the clock circuit. A disadvantage of such an arrangement is the relatively high outlay in circuitry involved in the execution of just one switching function. A further disadvantage resides in the fact that in the event of any interruption in the current supply the store is erased and the information has to be restored into it.

This invention seeks to provide a clock in which at least the former disadvantage is reduced.

According to this invention there is provided an electronic digital clock having at least one time-programmed electrical output for triggering switching functions, the clock comprising a digital electrical time display, a clock circuit for producing and applying to said display coded signals representing time, a multiplexer, at least one coded fixed-value store, a sampling logic circuit and a comparator circuit, wherein coded values stored in the fixed-value store are sampled under the control of the multiplexer by the sampling logic circuit and are compared in the comparator circuit with said coded signals representing time, and wherein in the event of coincidence between the sampled values and the coded signals representing time an output signal is produced at said time-programmed electrical output.

It is possible in this fashion to provide a virtually arbitrary number of stores without increasing the outlay in circuitry as a consequence of the number of stores. By using fixed-value stores which comprise coding switches, it is also possible to contrive that even after an interruption in the current supply, the stored value previously written in is retained un-disturbed. A further advantage resides in the fact that the stored values adjusted can be read out at any time, i.e. it is possible at any desired time to determine which store is set to which value.

The invention will be further understood from the following description by way of example of embodiments thereof with reference to the accompanying drawings, in which:

FIG. 1 shows a schematic circuit diagram of a clock in accordance with an embodiment of the invention and having two stores;

FIG. 2a shows a block schematic illustration of the circuit diagram of FIG. 1;

FIG. 2b shows a block schematic illustration of the circuit diagram of a clock which is similar to that shown in FIG. 1 but which has more than two stores;

FIG. 3a illustrates signals which occur in operation of the clock shown in FIGS. 1 and 2a;

FIG. 3b shows a logic table for the coding of days of the week for the clock shown in FIGS. 1 and 2a;

FIG. 4 shows a block circuit diagram of the clock shown in FIGS. 1 and 2a;

FIG. 5 shows a schematic circuit diagram of a clock in accordance with another embodiment of the invention;

FIG. 6 illustrates signals which occur in operation of the clock shown in FIG. 5.

FIG. 7 illustrates a data carrier in the form of a punched card used as a fixed-value store, and

FIG. 8 illustrates a fixed-value store in the form of coding switches.

Referring to the drawings, in FIGS. 1 and 4 a block 1 represents a frequency standard, which may be a crystal-controlled oscillator or the normal AC mains. Pulses from the frequency standard are applied to a clock switching circuit 2. The clock circuit 2 produces at an output 4 binary coded decimal (BCD) signals which are applied to a display logic circuit 11 which is connected to a display device 12, for example a seven segment display. The clock circuit 2 also supplies pulses to a multiplexer 3 which in turn determines a switching sequence of the coded signals at the output 4 and the display logic circuit 11. Between the output 4 and the display logic circuit 11 there are four individual lines (1), (2), (4) and (8) for the BCD signals, as is known per se. The elements 1, 2, 3 and 11 are shown in FIG. 1 within a block 14. If the frequency standard 1 is a crystal-controlled oscillator, the clock is preferably battery powered. If the frequency standard 1 is the normal AC-mains, however, the clock is preferably powered from these AC-mains.

The multiplexer 3 has a further output which is connected to a sampling logic device 8. A frequency f.sub.1 produced at this further output is the same as the frequency produced at the multiplexer outputs which are connected to the display logic circuit 11 and the clock circuit 2.

The sampling logic device 8 successively samples the individual decades of BCD fixed-value (read-only) stores 9 (9' and 9" in FIG. 1). The sampled stored values are applied to a BCD input 7 of a comparator circuit 6. The comparator circuit 6 has a further BCD input which is connected to a BCD output 5 of the clock circuit 2. If the stored values coincide with the BCD output signal appearing at the output 5 of the clock circuit 2, then the comparator circuit 6 applies a signal to an output 13. The stores 9 are coded BCD fixed-value stores. These stores operate with switching contacts and the coded input can be effected through the medium of digital reels, coded cards for insertion into a reader, punched cards, punched tapes and other fixed-value data carriers. Instead of switching contacts, other switching elements can be provided. Each store is subdivided into decades. In the illustrated example, each store 9 has five decades, namely a decade 15 for tens of hours, a decade 16 for units of hours, a decade 17 for tens of minutes, a decade 18 for units of minutes, and a decade 19 for the day of the week and an on/off switching function.

A data carrier of current or tape type in the form of a punched card is illustrated in FIG. 7 for use as a fixed value store 9. The tapes are punched or perforated according to the switches (on/off) of the decades of store 9' in FIG. 1.

The fixed-value store 9' according to FIG. 1 can further be constituted by coding switches of the type shown in FIG. 8, having reels divided into decades, namely a decade 15 for tens of hours, a decade 16 for units of hours, a decade 17 for tens of minutes, a decade 18 for units of minutes, a decade 19 for the day of the week, and an on/off switch.

The individual stores 9 and their decades are sampled as follows: the multiplexer 3 supplies pulses to a digit driver having outputs D.sub.1 to D.sub.6 at the frequency f.sub.1. The driver output D.sub.1 is connected to an input of each of gates G.sub.15 which are associated with the decades 15 of all the stores 9. The same applies to the driver outputs D.sub.2 to D.sub.5 in relation to gates G.sub.16 to G.sub.19 respectively. On the occasion of a first sampling pulse of sampling frequency f.sub.1 (see FIG. 3a) a pulse is supplied to all the gates G.sub.15, on the occurrence of a second sampling pulse, via the driver output D.sub.2, all the gates G.sub.16 are supplied with a pulse, and so on until after a fifth sampling pulse. Another input of all the gates G.sub.15 to G.sub.19 associated with each store is connected to an output of a bistable trigger stage (in the case of two stores, as shown in FIGS. 1 and 2a ), or a shift-register (in the case of more than two stores, as shown in FIG. 2b). In the example shown in FIG. 1, an input of all the gates associated with the store 9' is connected to the Q output, and an input of all the gates associated with the store 9" is connected to the Q output of a bistable trigger stage 20 which is supplied by the multiplexer 3 with pulses at a frequency f.sub.1 /6. Thus with five successive pulses at the sampling frequency f.sub.1 the decades of one store are successively sampled, and after a sixth pulse at the sampling frequency f.sub.1 with the next five pulses at the sampling frequency the decades of the next store are sampled.

The sampled values from the stores are fed via lines (1), (2), (4) and (8) to the BCD input 7 of the comparator circuit 6. As illustrated in FIG. 1 the comparator circuit compares the stored values on the lines (1) and (8) and appearing at the input 7 with those of the BCD output 5 of the clock circuit 2. Identical circuits (not shown) are also provided for the lines (2) and (4). The outputs of the individual comparator circuits are taken to a gate G.sub.20 whose output is connected to the input of a five-stage counter 21. This counter is advanced one step whenever coincidence occurs between the BCD clock signal and the sampled BCD store signal. When five coincidence situations have been detected in a store 9, i.e. a coincidence for each decade, the counter 21 applies an output signal to the output 13. If, during sampling of a store, one of the coincidences should be absent then the counter 21 does not produce any output signal. In order that the counter 21 can be reset to zero on completion of sampling of a store 9, a reset input of the counter 21 is connected to the digit driver output D6. This has the result that in each case with the sixth sampling pulse of frequency f.sub.1 the counter 21 is reset to zero.

The output signal at the output 13 must be applied via an address logic circuit to the correct unit output. In FIG. 1 unit outputs 22' and 22" are assigned to the stores 9' and 9" respectively. Gates of the address logic circuit for the unit output 22' are consequently connected to the Q output of the bistable stage 20, and gates for the unit output 22" are connected to the Q output of the bistable stage 20. In this fashion a correct relationship between the store just sampled and the associated unit output is ensured. The unit outputs of the address logic circuit may be connected to further lines which transmit values for a process control.

In order to determine whether the switching function is to produce an on or off condition, one of the coding switches of the decade 19 in each store 9 is allotted to this function. Consequently, the line (8) of each store 9 is taken directly to a gate at the output 13. By means of this gate, a reversal of the sign of the output signal is produced when the coding switch of the store 9 just sampled and producing an output signal is closed.

In order to code the days of the week the remaining three coding switches of the decade 19 in each store are used. Accordingly, in this respect coincidence need only be achieved in relation to the values on the lines (1), (2) and (4). If, however, a time value fed into a store is to perform a daily switching function, then in this case a by-pass circuit is provided which by-passes the comparator circuit 6. In accordance with the logic table for the fifth decade as shown in FIG. 3b, as shown in the first line of the table all three coding switches are open in respect of the daily switching condition. When sampling the fifth decade of a store 9, therefore, the zero-values are present on the associated lines (1), (2) and (4). These values are applied to an OR-gate which then arranges that the counter 21 is advanced one step, even if, via the comparator circuit 6, no coincidence signal is produced in respect of the fifth decade.

In the clock described above the most important electronic components are contained in an integrated circuit, which is defined in FIG. 1 by a box 29' and which has at least 23 connections which have to be established outside the switching block.

It is possible to simplify the arrangement, and in particular to reduce the number of connections to the integrated circuit, as described below with reference to FIG. 5.

In the circuit shown in FIG. 5 the clock circuit 2 has only one BCD output, referenced 4(5), instead of two. This BCD output is connected both to the display logic circuit 11 and to the comparator circuit 6. The seven outputs of the display logic circuit 11 are connected to a changeover switch 28 to which in turn the inputs 27 of the comparator circuit 6 are connected. Furthermore, seven lines extend away from the changeover switch 28.

A bistable trigger stage 20' has a modified switching sequence compared with that of the stage 20 of FIG. 1, as shown in FIG. 6. In each case after six pulses from the digit driver outputs D.sub.1 to D.sub.6, a switching unit signal U is applied to the changeover switch 28. Outputs I and II of the bistable stage 20' are connected to the gates associated with the stores 9' and 9" respectively. During a first six sampling pulses from the digit driver, the switching signal U and the output I carry a high value. Consequently, all the gates associated with the store 9' are enabled and at the same time in the changeover switch 28 the BCD inputs 7 which are marked (1), (2), (4) and (8) are connected to the inputs 27 of the comparator circuit 6. In this fashion, the store 9' is sampled. After the six sampling pulses have been produced, the switching signal U and the outputs I and II all have a low value. Sampling of the stores is consequently inhibited but in the changeover switch 28 the seven outputs 26 of the display logic circuit 11 are connected to the seven output lines of the change-over switch 28. These seven output lines are connected to a LED driver 23 which in turn drives a display device 24. Via a display driver 25 the display device 24 is furthermore supplied with five pulses from the digit driver, this having the result that the display device 24 is up-dated during these five pulses. After a sixth pulse from the digit driver the switching signal U again adopts a high value and at the same time the output II acquires a high value while the output I remains at the low value. During the next six sampling pulses, the gates associated with the store 9" are driven and the BCD input 7 of the change-over switch 28 is connected to the input 27 of the comparator circuit 6. In this fashion, the store 9" is sampled. After the sixth sampling pulse, once again the display logic circuit 11 is connected to the display device 24.

Thus, the operating sequence of this arrangement is: sampling of the store 9', application of signal to the display device 24, sampling of the store 9", application of signal to the display device 24, etc.

As FIG. 5 clearly shows, four of the seven lines provided for the connections to the devices 23, 24, are employed simultaneously as BCD lines for the stores. The fifth line is required to choose the input frequency, e.g. 50 or 60 Hz. The remaining two lines perform minute and hour setting-up functions. The display device 24 is an opto-electronic device. The clock includes switching elements which serve to effect correctly timed setting up of the display device 24 and to erase or zero the display device and the clock circuit or parts thereof.

In many instances, with programmable clocks of this kind, it is unnecessary to have a frequently changing store program, the fixed-value stores instead having a program which need not be altered for long periods of time e.g. months or years. In such cases, each fixed value store can consist of a permanently wired circuit board which can be plugged in using a plug strip. The program can then be very quickly altered by exchanging the circuit boards.

Such circuit boards may be double-sided, i.e. printed on both sides, and may carry the entire circuitry for the stores 9, each of which as shown in FIGS. 1 and 5 comprises a matrix at each intersection point of which is provided a switch connected in series with a diode. In this case the conductors may be so routed initially all the switches are closed, and then for programming purposes it is simply necessary to interrupt lines which are to constitute open switches. This can for example be done by perforating the circuit board at a particular conductor. It is alternatively possible to use a printed circuit board which is printed on one side only. In this case initially all the switches may be open and closed switches may be established by soldering in wire bridges. It is also possible in this situation to use so-called wire-wrap pins. Naturally any other suitble form of store may be used.