JPS5812592B2 - Camera power supply voltage checker - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a device for checking the voltage of a power supply battery of a camera, particularly for cameras equipped with a digital display device that displays various photographic information in patterns such as numbers and symbols in a viewfinder or the like. This relates to a power supply voltage checker.

2. Description of the Related Art Cameras equipped with automatic exposure control devices based on digital signals have been proposed that are equipped with display devices that display various types of photographic information in patterns within a finder or the like.

That is, the shutter speed, aperture value, etc. are displayed as a character pattern by a combination of light emitting elements activated by digital signals, and in order to do this, a decoder, a 7-segment driver, etc. are used as the display device.

Conventionally, power supply voltage checks in cameras like this have been carried out by blinking a separately provided check lamp, but this method requires space to incorporate this checker into the camera, which has many inconveniences. Ta.

SUMMARY OF THE INVENTION An object of the present invention is to provide a checker in which the display device for photographing information in a digital automatic exposure control camera as described above is also used to check the power supply voltage, and the suitability of the voltage is displayed in a character pattern. It is.

For example, in a digitally controlled EE camera, photographing information, ie, shutter speed and aperture value, are read out from the TV register and AV register of the control device and displayed in the finder as numbers and symbols.

At this time, in TTL single-lens reflex cameras that have a photometric element placed inside the viewfinder, in order to prevent stray light from entering the photometry unit from the display unit, etc., from causing photometry errors,
There is a method of time-sharing the operating time of the photometer and the operating time of the display.

For the display section of such a device, there is a method of dynamically displaying information in the form of numbers and symbols using, for example, a 7-segment light emitting diode.

That is, digital signals from the TV register and AV register of the control device are decoded and displayed as character patterns.

In the present invention, the decoder of the display device as described above, 7
Using segment drivers, light emitting diodes, etc.
The appropriateness of the power supply voltage is displayed in the viewfinder as a character pattern.

The present invention will be explained below with reference to the figures.

FIG. 1 is a circuit connection diagram showing an embodiment of a digital display unit equipped with a power supply voltage checker according to the present invention.

In the figure, E is a power supply battery, Sw1 is a power switch, and C is a digital exposure control device.

S vv2 is a switch for checking the power supply voltage, RA is a variable resistor that divides the power supply voltage to obtain the voltage to be measured, RB is the resistance of the voltage divider circuit to obtain the reference voltage, and DZ is the zener to obtain a constant voltage. The diode D is a comparison circuit that compares the reference voltage and the voltage to be measured to obtain a differential voltage.

The output of the comparison circuit D is input to the decoder of various photographic information digital display devices.

D1 to D8 in the figure are lines for displaying information, and read signals from the TV and AV registers are input to the decoder as shown in the figure and converted into 7-segment signals, and the output is sent to multiple segments via the driver DA. The signal is applied to the LED group of light emitting diodes, and the TR is time-divisionally switched by a timing pulse from the terminal TDX, and numbers and symbols are displayed in the viewfinder etc. by the combination of LEDs.

The output of the power supply voltage check circuit is applied to the PF line of the decoder, and when the power supply voltage reaches vA s, outputs are generated at d, e, and f of the decoder, thereby causing the LED a
, e, f elements light up.

FIG. 2 is a diagram showing the arrangement of the 7-segment LEDs, and the diagram shows a state in which d, e, and f are lit to display "L".

This gives a warning that the power supply voltage is below the reference value and is inappropriate.

This display is also performed in a time-division manner using timing pulses from TDX.

In the apparatus shown in the figure, to check the voltage of the power supply battery E, first turn on the power switch S vv t to put the camera's exposure control circuit C into an operating state, and then turn on S vv 2.

As a result, the terminal voltage of battery E is divided by RA, and a voltage A proportional to E is generated at its movable terminal.

In addition, the voltage divider circuit consisting of RB and Zener diode DZ maintains a constant reference voltage VB regardless of fluctuations in battery voltage E.
is obtained.

These two voltages are input to a comparator circuit D, such as a differential amplifier, and a differential voltage is outputted to its output.

Now, by adjusting the variable resistor RA so that when the battery voltage reaches the lower limit of the voltage suitable for operating the device, ■ A = Vs, ■ When A becomes lower than Vs, the output of D A positive voltage can be generated at

When this output is sent to the PF line of the decoder, the 7-segment decoder driver circuit operates as described above, and the second
Of the light emitting diodes arranged as shown in the figure, d, e, f
The element emits light and displays "L".

This gives a warning that the battery voltage is too low.

Note that if the voltage is at a value suitable for the operation of the device, no warning will be displayed even if SW2 is turned on.

The above voltage check is performed in a time-division manner by inputting a timing pulse for operating a decoder etc. from the TDX terminal to turn on the transistor TEL.

Therefore, the warning display LED is replaced with the information display L of the exposure control device.
It is also possible to display it in a time-division manner by sharing it with ED.

As described above, the power supply voltage checker of the present invention can be constructed by simply adding a small number of components to the photographic information display device of the camera, so it is easy to incorporate these devices into the camera, and the voltage check display is easy. is clearly displayed by a character pattern, making it a convenient device to use.

[Brief explanation of the drawing]

FIG. 1 is a circuit connection diagram showing an embodiment of the display section of a digitally controlled camera equipped with a power supply voltage checker according to the present invention;
FIG. 2 is a diagram showing the arrangement of light emitting diodes used in the device of the present invention. E...Power battery, Sw1...Power switch, Sw2...
Check switch, C...digital automatic exposure control circuit,
RA...Variable low resistance, RB...Resistor, D7,...Zener diode, D...Comparison circuit, DA...Driver, L
ED...Light emitting diode, TR...Transistor, TD
X...Timing pulse input terminal.

Claims (1)

[Claims] 1 The camera is equipped with a digital display device that displays various photographic information as various segment patterns using a segment type digital display element, and when checking the power supply voltage of this camera, the voltage is compared with a reference voltage to obtain a difference output. A power supply voltage checker for a camera, characterized in that a circuit is provided, the output is input to the segment type digital display device, and the digital display element displays a segment pattern different from the display of the photographing information.