JPS58108519A - Power supply checking device for camera - Google Patents

Abstract

PURPOSE:To discriminate a power voltage checking level in accordance with the temperature characteristics of a driving system by changing the level in proportion to temperature. CONSTITUTION:When a switch SW1 is turned on, constant voltage VF is applied from a battery E to an inverting terminal of a comparator AMP1 through a constant voltage circuit REG. On the other hand power voltage Vcc is divided by registors R2-R4 and a thermistor RS and applied to a non-inverting terminal of the comparator AMP1. Since the same condition as actual driving is prepared by a dummy registor R1, a light emitting diode LED is turned on when the power voltage is sufficiently supplied. The registers R2-R4 and the thermistor RS are selected in accordance with the temperature characteristics of the driving system, so that the check level is set up in proportion to the feeding capacity of the driving system.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention is a power supply check device for a Hiro camera.

In cameras that have a built-in battery as a power source for the motor drive of the film feed and shutter mechanism, and the exposure control device,
Devices for checking and displaying whether the power supply voltage is above a certain value necessary for rounding the operation of a camera are generally known. Conventionally, in such power supply checkers, if the check level, which is set to a constant value, fluctuates due to temperature changes, an insufficient voltage will be displayed even though the voltage is above a certain value, and on the other hand, it will be displayed that the voltage is sufficient. Even though the voltage is actually low, the motor etc. may not operate.To prevent this, a temperature compensation circuit etc. is used to prevent fluctuations in the check level and ensure accurate checking. I made sure it was done.

However, in cameras such as those mentioned above that drive the film feeding mechanism with a motor, the load on the feeding mechanism in the motor fluctuates depending on the temperature, and even if the power supply voltage is above the set check level, the film cannot be fed. There are cases where there is sufficient feeding capacity even if the check is not performed normally and the check level is below.

Generally, at room temperature, the load on the drive system of the motor-based feeding mechanism is lighter than at low temperatures, and the film can be stably fed even if the battery voltage is low.

However, at low temperatures, the load on the drive system becomes heavy, resulting in an increase in current consumption and a decrease in feeding capacity.

In particular, when the temperature drops below -5°C, the drive system's load changes exponentially with respect to the temperature difference, and the feeding capacity is extremely reduced compared to room temperature. In view of the above, the present invention provides a power supply check device that can check the actual feeding capacity by changing the check level of the power supply in accordance with the change in the load of the drive system due to temperature changes. It is something.

The present invention will be described below with reference to embodiments. Fig. 1 is a schematic diagram showing an embodiment of the present invention. In the figure, E is a power supply battery, SWl is a battery check switch, REG is a constant voltage device, and R1 is a camera drive. Dummy resistance equivalent to the system load, R2e RN and R4 are the power supply voltage W
A dividing resistor that divides oe, f(S indicates a thermistor with a negative characteristic that changes depending on ai&.) MP1 is a comparator, and the inverting terminal (-) K is the constant voltage V of the RIG.
F and the non-inverting terminal (+) are each supplied with a divided voltage from the dividing resistor. R and R are limiting resistors, LED is a display light emitting diode, and TR is a transistor that drives IJD.

In the above circuit, battery check switch SWI
When turned on, a constant voltage VF is supplied from the battery E to the inverting terminal of the comparator AMP1 via the constant voltage circuit I (EG). 'Th' for resistance and H path resistance!
Under Th, the conditions which appear to be the same as those during actual driving are created.

The voltage Vcc of the power supply is divided by the resistor R2, the resistor R4 and the thermistor R8, and is supplied to the non-inverting terminal (+) of the humpator AMPi.

The output terminal of AMP1 becomes 1H" level, and the resistance R.

The transistor TRI is made conductive through the transistor TRI, and the light emitting diode LED is turned on. As a result, when the power supply voltage becomes high, the output terminal of the comparator AMP1 becomes @L'' level, making the transistor TRs non-conductive and causing the light emitting diode L to become non-conductive.
'Turn off I&D.

The check level can be set according to the actual feeding capacity of the drive system.

Figure 2 is a diagram showing the temperature characteristics of the voltage check level.
As shown in the diagram, where the horizontal axis shows temperature and the vertical axis shows voltage check level, the difference in check level is small when changing from room temperature to high temperature K for an 11 degree change, and conversely, when going from room temperature to low temperature, the difference in check level is small. The temperature characteristics are changed exponentially so that the value increases.

As mentioned above, in the present invention, the voltage check level is configured to change in accordance with changes in the load on the drive system caused by temperature changes, making it possible to determine the actual drive capacity at any temperature with extreme reliability. A high power check meeting can be obtained.

[Brief explanation of the drawing]

FIG. 1 is a diagram showing an embodiment of the present invention, and FIG. 2 is a diagram showing the relationship between temperature and voltage check level in the embodiment. g: 1g pond, sw□: battery check switch. Rge: Constant voltage device, R1: Dummy resistor, R2e l
(s e R4: division resistor, R8: thermistor, AMP
l: Comparator, Rls, R.: Limiting resistor, LED
: Display light emitting diode, TR, : ) Tenjista applicant Nakayanon Co., Ltd.? =4. To i

Claims (2)

[Claims] (1) A power supply check device for a camera that includes a built-in electric drive device and a power supply battery, characterized in that the check level of the power supply voltage is changed in accordance with load fluctuations due to the temperature of the electric drive device. (2) Adjust the check level of the power supply voltage according to the temperature.