Patent GB-1342164-A (GB)
Title: Solid state watch
IPC: G04G9/00
Filed: 1971-04-19
Abstract: 1342164 Electronic watches HAMILTON WATCH CO 19 April 1971 [6 May 1970] 23636/71 Heading G3T A rechargeable battery powered solid state electronic wrist watch comprises a crystal controlled oscillator time base the output frequency (32, 768 Hz) of which is divided down by a series of integrated circuit binary counters (MOS flipflops) and time display on demand (persisting for 1“ sees) with alpha-numeric characters formed from a 27 dot or 7-segment array of lightemitting diodes (Ga As P) or alternatively liquid crystal or other electro luminiscent means (not disclosed). Intensity of display is controlled by three photo-transistors in dependence on ambient light conditions. Hours and minutes only are normally displayed. Seconds are displayed only on continued interrogation - A coloured filter screen passes cold red light from the light emitting diodes. The hours can be set rapidly without disturbing the minutes and seconds. The minutes can also be rapidly set, the seconds being automatically zeroed in the process. An auxiliary battery or a capacitor may be provided, which continues to supply power during the five minute period required to replace the main battery with a fully charged one. GENERAL ARRANGEMENT OF CIRCUITRY - (Figs. 4a and 4b). The output of oscillator 96 is divided by counters 100, 104, 106, 108, 110 to give a 2 Hz pulse train for use during setting. The 8 Hz output of counter 108 is also applied to a Set Hold circuit 114 and appears at an output thereof, from which it is transmitted to a counter 118 and converted to a 1 Hz pulse train. The 1 Hz train is further divided by counters 122, 124, 126, 128, 130 the binary coded decimal outputs of which respectively activate decoder drivers which cause energization of the appropriate hours, mins and sees displays. The displays are turned ON and OFF intermittently during the interrogation period in order to conserve power, and at a frequency determined by a light intensity control circuit 168. Pulses to effect the intermittent action are applied to the decoder drivers by display control drivers 160 in accordance with a signal from the light control circuit 168. Under full day light conditions the output of the control drivers 160 is D. C. so that the diodes are lit during the whole of the interrogate period i.e. 100% duty cycle. Under lesser ambient light conditions a 50% duty cycle is obtained by applying a 64 Hz signal, derived from counter 106, to the display diodes. A 25% duty cycle is produced by a pulse train obtained by combining of 64 Hz and 128 Hz waveforms from counters 104, 106, i.e. a pulse is produced for every positive coincidence of the 64 Hz and 128 Hz waves. For a 12¢ % duty cycle a 256 Hz wave is combined with the other two waveforms. Logic circuitry to effect this light intensity control is illustrated in Fig. 5, (not shown). Actuation of a demand button by the watch wearer causes a "read" switch 184 to close thereby connecting a positive supply to the display control drivers 160 resulting in the illumination of the hours and minutes display only. In addition a positive supply is connected to Set Hold circuit 114 which immediately resets a timer 192. After 1“ sees the timer produces an output pulse on a lead 196 causing the display control drivers 160 to change state and extinguish the hours and minutes displays. Simultaneously the control drivers output is applied via a line 162 causing the seconds display to be illuminated. SETTING. Closure of "hours set" switch 198 causes a circuit 200 to pass a 2 Hz pulse train on a lead 206 to the hours counter 130 via a lead 208. In addition it causes an output from the display control drivers 160 to ensure that the hours and minutes displays are illuminated during Hours setting. Likewise closure of "Minutes set" switch 212 results in the application of a 2 Hz pulse train to the minutes counter 126 and illumination of the hours and minutes displays. Setting the minutes stops the watch and also zeros the seconds in order to synchronize the watch with a radio signal for example. The watch starts again when the "read" button is pressed. The display modules, dividers and encoders are encased in a potting compound comprising a clear silicon rubber coating.