JPS584798B2 - Digital Hiyoji Dokei - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a digital display clock that displays time using digital values using a glow discharge tube, and is configured such that the lighting brightness of the glow discharge tube automatically changes depending on the level of ambient illuminance. This is what I did.

There are various types of digital display watches that use glow discharge tubes to display the time using digital values, but in most of them, the brightness of the display is constant, so the brightness is insufficient in bright places and the brightness is low in dark places. There is an inconvenience that it becomes excessive.

On the other hand, the voltage applied to the glow discharge tube is controlled by a photoconductive element connected to this voltage supply system circuit to change the lighting brightness of the glow discharge tube depending on the ambient illuminance.

However, in this case, since the applied voltage cannot be lower than the discharge sustaining voltage, the brightness adjustment range is correspondingly narrower, and furthermore, it is difficult to maintain low brightness lighting stably.

The present invention has been made in view of this point, and will be explained in detail below using actual cases shown in the drawings.

In Figure 1, a 60Hz, IOOV commercial AC power supply 1
The transformer 2 which connects the primary winding to the
A sinusoidal low voltage as shown in Figure a is induced, which is converted into direct current by the rectifier 3 and smoothing capacitor 4.

This DC output is applied to a load resistor 5 and a switching transistor 6.
The transistor 6 is controlled on and off by an alternating signal sent from the secondary winding through the integrating circuit.

Therefore, a 60 Hz rectangular pulse signal as shown in FIG. 2B appears between both terminals of the load resistor 5, and this pulse signal is applied to the pulse counting circuit 7 and the transistor 8.

Each time 3,600 input pulses (3,000 in the case of a 50Hz power supply) are applied, the pulse counting circuit 7 calculates 1
In addition to generating a minute signal, it also generates a 10 minute signal, an hour signal, and a 10 hour signal, and these D signals are transmitted by the transistor switch circuit group 9.

Thus, the switch circuit group 9 selectively connects the cathode group of the glow tube 10, which has a four-digit time numeric display function, to the ground point.

On the other hand, the capacitor 11 connected between the emitter and collector of the transistor 8 is charged by the charging current through the photoconductive element 12, the parallel variable resistor 13 for sensitivity adjustment, and the variable resistor 14 during the cutoff period of the transistor 8. The charges accumulated in the transistor 8 are discharged when the transistor 8 is inverted to conductive.

The photoconductive element 12 is provided with its light-receiving surface facing outside the device, and changes its resistance value depending on the ambient illuminance, and changes the emitter potential of the transistor 8 depending on the ambient illuminance.

The variable resistor 14 has a larger resistance value than the parallel connection of the photoconductive element 12 and the variable resistor 13, and the CR time constant of this charging/discharging circuit is mainly determined by the capacitor 11 and the variable resistor 14.

Therefore, the second
The waveform inclination angle of the sawtooth signal shown in FIG. C changes mainly by adjusting the variable resistor 14.

Also, the voltage level of this sawtooth signal is
In other words, the resistance value changes depending on the ambient illumination.
It changes within the range shown by the broken line.

Therefore, if the operating point potential of the Schmitt trigger circuit 15 is set to e volts as shown in FIG. The pulse width changes as shown in FIGS. 3b to 3d depending on the ambient light intensity, and the pulse width is small when the ambient illuminance is high, and large when the ambient illuminance is low.

According to the device of the present invention, the power supply line to the glow discharge tube 10 is interrupted at minute intervals using such an illuminance-dependent rectangular wave pulse signal, and in this actual case, the signal output of the unit 1 trigger circuit 15 is switched. It is applied to circuit group 9.

Thus, the glow discharge tube 10 is illuminated by a voltage modulated at a frequency of 60 Hz to display the time, and its luminance increases when the ambient illuminance is high and decreases when the ambient illuminance is low, depending on the change in the duty cycle. .

The glow discharge tube 10 has four digits for displaying four-digit time numbers.
In addition to the built-in display units 101 to 104, there is also an auxiliary display unit between the hour numeral display position and the minute numeral display position.
It is equipped with 05.

The auxiliary display unit 105 consists of an anode A and a cathode K facing it, just like the other four display units, but since it receives power directly from the DC power supply without going through the switch circuit group 9, the operation of the device is The inside lights up at a constant brightness regardless of the level of ambient illuminance.

This lighting not only serves as a pilot lamp, but also serves as a visual separation between hour and minute displays, and is also a keep-alive light that maintains the ionization of the gas within the discharge tube. Acts as an electrode.

Therefore, not only can the operating status of the device and the time display be accurately grasped, but even if the voltage application to the display units 101 to 104 is intermittent as described above, the occurrence of ignition delays and uneven lighting can be prevented. Ru.

According to the above actual case, a PNP type transistor was used as the transistor 8, and a sawtooth wave signal was extracted from the variable resistor 14 connected to its collector circuit.
A circuit configuration as shown in the figure can be adopted.

In addition, in the circuit configuration shown in FIG. 4, the slope angle of the sawtooth wave voltage taken out to the collector of the transistor 6 changes more as the ambient illuminance changes, rather than its peak voltage, so that the brightness changes more smoothly. There are advantages to doing so.

16 indicates a phase inversion transistor.

According to the above embodiment, the generation source of the basic rectangular wave signal for intermittent power supply to the discharge tube and the signal source of the time measurement system are common, but these may be formed separately; A free-running oscillator can be used as a signal source.

Further, the latter is not limited to AC power synchronization, and a crystal oscillator can be used for the latter or both.

Furthermore, it is also possible to apply a so-called dynamic operation (multiplex operation) in which the voltage application to the anode of the glow discharge tube 10 is sequentially shifted.

Furthermore, although a photoconductive element was used in the above embodiment,
When a phototransistor is used as the transistor 8, this can be omitted.

As is clear from the above description, according to the digital display timepiece of the present invention, the duty cycle of the pulse wave signal that connects and disconnects the power supply line to the glow discharge tube for time display is changed depending on the ambient illuminance. When the glow discharge tube is turned on, the brightness of the time, which is displayed as a digital value, changes automatically and continuously over a wide range depending on the ambient illuminance. Rationalization can be achieved by lighting each at low brightness.

Furthermore, by providing an auxiliary display unit in the glow discharge tube and lighting it at all times, glow discharge can be generated stably at all times.The present invention can be particularly applied to alarm clocks, etc., and has excellent practical effects. play.

[Brief explanation of the drawing]

Fig. 1 is an electric circuit diagram of a digital display timepiece embodying the present invention, Fig. 2 is a voltage waveform diagram at each part of the circuit, Fig. 3 is a diagram showing input signal waveforms and output signal waveforms of the Schmitt trigger circuit, and Fig. FIG. 4 is an electrical circuit diagram of a main part of another embodiment of the present invention. 6... Switch transistor, 7...
・Pulse counting circuit, 9...Transistor switch circuit group, 12...Photoconductive element, 15...
...Schmitt trigger circuit.

Claims (1)

[Claims] 1 Connect a Schmitt trigger circuit to the power supply line of the glow discharge tube for time display, drive the Schmitt trigger circuit using a sawtooth wave signal whose voltage level changes depending on the ambient illuminance, and pulse-light the glow discharge tube. A digital display clock characterized by: