JPS62223739A - Device for alarming battery life of camera - Google Patents

Abstract

PURPOSE:To fix the number of shots from the generation of an alarm to operation down under any temperature condition and to always alarm accurate battery life by setting up an alarm level in accordance with the temperature characteristics of the battery which may be changed by the temperature condition at the time of photographing. CONSTITUTION:Counters 7, 8 count up the number of shots in the strobe photographing and normal photographing of a camera respectively input respective count values to a counter 10 through an OR gate 9 to count up the number of shots at the time of photographing. The counted number of shots is converted into plural analog signals by a decoder 11 and the analog signals are applied to analog switches 2-4. On the other hand, voltages Vck1-Vck3 set up in accordance with the temperature conditions at the time of photographing are applied from an alarm level generating circuit 1 to the switches 2-4. The voltages Vck1-Vck3 are selected by the analog signals corresponding to the number of shots and the alarm level is set up in an alarm circuit 6 by a comparator 5, so that always accurate battery life can be alarmed.

Description

DETAILED DESCRIPTION OF THE INVENTION (Field of Application of the Invention) The present invention relates to an improvement in a camera battery life warning device that warns that the battery life is nearing end by detecting that the battery capacity has reached a warning level. It is something.

(Background of the Invention) FIG. 4 shows the discharge characteristics of a lithium battery commonly used as a power source for cameras. In this figure, temperature is used as a parameter, the horizontal axis shows the number of shots N (weighted by strobe shooting and normal shooting), and the vertical axis shows the distance between the terminals of the battery when a predetermined load current is applied. Voltage C, C,
V, respectively, and the prohibition level Vcs is
Below that voltage, the camera will not operate properly. As can be seen from this figure, the lower the temperature, the lower the number of shots that can be taken (maximum number of shots NWaX), but the voltage drop rate relative to the number of shots near the prohibition level Vcs, that is, the slope of the curve, is gentler. At relatively high temperatures (above room temperature), there are parts where the terminal voltages C, C, and V are approximately constant regardless of the number of shots, and the number of shots that can be taken increases, but the prohibition level vC5
The slope of the curve becomes larger in the vicinity.

Now, if the level at which a warning is issued is Vck, the voltage between the terminals of the battery C, C, V will vary from the warning level Vck to the prohibition level V.
Number of shots Nb (N
bl, Nb2, Nb5) differ depending on the temperature as shown in FIG. However, with conventional devices, the number of shots that can be taken decreases due to temperature changes during shooting.
A warning is issued when the voltage between the terminals of the battery C, C, V when a predetermined load current is applied falls below the warning level Vck, which is set at a certain level, even though ax changes significantly. Because it is configured as follows,
As mentioned above, there is a problem in that the number of shots Nb that can be taken after the warning is issued is not constant.

Furthermore, if you continue shooting at temperatures above room temperature, the warning level Vck
If the camera is taken to a low temperature when the voltages C, C, and V between the terminals have dropped to a point close to that point, the camera may not operate at all. In other words, there are cases where the camera stops operating at all due to a dead battery even though no warning has been issued.

This is because the apparent capacity of the battery changes depending on the temperature; for example, when the battery capacity is 80% depleted, the terminal voltages C, C, and V vary considerably depending on the temperature. On the other hand, if an attempt is made to solve the above problem by setting the warning level Vck high in advance, a warning will be issued immediately at low temperatures, making it extremely difficult to use.

(Objective of the Invention) The object of the present invention is to solve the above-mentioned problems, and to make it possible to maintain a constant number of shots from the time a warning is issued until the device becomes inoperable, regardless of the temperature conditions. It is an object of the present invention to provide a battery life warning device for a camera that can always give an accurate battery life warning.

(Features of the Invention) In order to achieve the above object, the present invention provides a counting means for calculating the number of shots by weighted counting the number of shots taken after battery loading, a warning level generating means for generating a plurality of warning levels, A warning level selecting means is provided for selecting a higher value warning level from the warning level generating means as the number of shots by the means increases, so that the warning level can be set according to the temperature characteristics of the battery which changes depending on the temperature conditions at the time of shooting. The feature is that a warning level can be set.

(Embodiments of the Invention) Hereinafter, the present invention will be described in detail based on illustrated embodiments.

First, an overview of the present invention will be described. If the voltage under each temperature condition is expressed as Vb1 to Vb3 when the number of shots before the battery reaches the prohibition level Vcs (the maximum number of shots that can be taken Nmax) is a predetermined number of shots Nb, then the second It will look like the figure. From this figure, it can be seen that if the warning level Vck is changed depending on the temperature, the number of shots Nb that can be taken after the warning is issued will always be constant. Therefore, the present invention aims to issue a warning that the battery life is nearing its end by counting the number of shots N and changing the warning level Vck according to the number of shots at that time.

Figure 3 shows the number of shots N and warning level V in an unimplemented example.
This shows the relationship with ck. Here, an example is shown in which the warning level Vck is divided into three levels (Vck+ to vck3).

The relationship between the number of shots N and the warning level Vck is N < N
I (7) time... vCk; Vck.

N1≦N<N217)...vck=vck2
When N2≦N...--V c k = V c
It is k3. Therefore, the voltage between the terminals of the battery C, C
, V drops below the warning level Vck, -Vck3, that is, a warning is issued within the shaded area. By doing this, it is equivalent to changing the warning level Vck according to the temperature conditions when photographing is performed. This is because the terminal voltage C decreases while the number of shots is small.
, C, and V decrease because it is considered that the camera is being used at low temperatures. This can be easily assumed from the above-mentioned FIG. 4. On the other hand, if the number of shots is large, the battery is exhausted to some extent.
This is because the fact that the device is operating normally without issuing a warning in this state means that the temperature is relatively high (about room temperature or higher).

FIG. 1 is a circuit diagram for realizing an embodiment of the present invention as described above. In Fig. 1, reference numeral 1 denotes a warning level generation circuit, in which a warning level Vck3 obtained by dividing the voltage of the power supply Vr is applied to the connection point a of voltage dividing resistors R1 and R2, and Vck2 is applied to the connection point a of voltage dividing resistors R2 and R3. V at the connection point C between piezoresistors R3 and R4.
ck.

occur respectively. 2, 3.4 are analog switches that are turned on when a high-level signal is input from a decoder (described later); 5 is a voltage between the terminals of the battery C, C, V from a C, C, V detection section (not shown); analog switch 2
A comparator 6 compares the warning level Vck inputted through any one of the above comparator 5 with a warning level Vck; 6 a warning circuit that issues a warning that the battery life is nearing when a signal of a higher level is inputted from the comparator 5; 7 , 8 are counters connected to a circuit (not shown) that generates one pulse when one strobe photography and one normal photography are performed, 9 is an OR gate, and 10 is the number of pulses input from the OR gate 9. That is, a counter 11 that counts the number of shots is a decoder that outputs a signal at the /\I level via one of the signal lines 12 to 14 according to the count content of the counter 10.

Next, the operation will be explained. When one photographing operation is performed, one pulse signal is generated in a circuit (not shown), and if the photographing at this time is strobe photography, the counter 7 counts up by one, and if the photographing is normal photography, the counter 8 counts up by one. counts up by one. Now, if the ratio of current consumption for each operation of normal shooting and strobe shooting is 1:10, then normal shooting is 100%
The counters 7 and 8 are set so that one pulse is generated in the counter 8 when the flash photography is performed ten times, and one pulse is generated in the counter 7 when the flash photography is performed 10 times.
It is a 0-base and 100-base counter. This is because the degree of battery consumption for one shot (N=1) needs to be constant no matter which mode photography is performed.

The pulse signal generated in the counter 7 or 8 is input to the counter 10 via the OR gate 9, and the count number of the counter 10 is incremented by one. It is assumed that the counters 7, 8, and 10 are all reset when the batteries are replaced with new ones.

The count a at the counter 10 is sent to the decoder 11,
The decoder 11 converts it into a signal corresponding to the count number at that time. In other words, the count number (shot number N) is N<Nl
, the analog switch 4 is connected via the signal line 14.
When N≦N≦N2, a high level signal is output to the analog switch 3 via the signal line 13, and when N2≦N, a high level signal is output to the analog switch 2 via the signal line 12. is output. Now, the count number of counter 10 is N<N
If it is 1, a high level signal is output to the analog switch 4 via the signal line 14, and the analog switch 4 is turned on. Therefore, in such a case, the warning level Vck generated at the contact point C will be used as the warning level.
, is selected. The warning level Vck is compared with the terminal voltages C, C, and V of the battery inputted from the C, C, and V detectors (not shown) by a comparator 5, and the terminal voltages C, C, and V correspond to the warning level Vck. If it is below, the comparator 5 outputs a high level signal.

As a result, the warning circuit 6 operates and issues a warning that the battery life is nearing its end.

Similarly, when N≦N×N2, the warning level Vck2 is
When N2≦N, a warning level Vck3 is selected by the decoder 11, and when the voltages between the terminals C, C, and V fall below the warning levels VcR2, VcR3, the warning circuit 6 indicates that the battery life is nearing its end. A warning will be issued that this is the case. As a result of the above, the relationship between the number of shots N and the warning level Vck shown in FIG. 3 has been realized.

According to this embodiment, the number of shots is weighted and counted according to the shooting operation, and the higher the count, that is, the greater the number of shots, the higher the warning level Vck is selected.As a result, the warning level Vck is determined depending on the temperature. This is equivalent to changing Vck, and the number of shots from when a warning is issued until the camera stops operating does not change depending on the temperature and remains constant. In other words, it becomes possible to issue accurate battery life warnings. Furthermore, as the number of shots N increases, that is, as the degree of battery consumption increases, the warning level Vck increases, so the warning level VCk3 is reached at the number of shots before the degree of consumption when the camera stops operating at low temperatures. If you take the camera to low-temperature shooting conditions when the voltages between the terminals C, C, and V drop to around the level Vcs, which prohibits continued shooting above room temperature, the camera will stop working at all. This eliminates the problem of being left behind. Conversely, if you set the warning level Vck to a level higher than the battery terminal voltage C, C, V at which the camera stops working at all when the camera is taken into a low temperature environment, the warning display will not occur. When it does not appear, the camera will operate no matter what temperature conditions it is placed in as long as it is within the camera's operating temperature range.

(Correspondence between the invention and the embodiments) In this embodiment, the comparator 5 serves as the comparison means of the present invention, the warning circuit 6 serves as the warning means, the counters 7, 8, 10 and the OR gate 9 serve as the counting means, the decoder 11 and the analog switch 2 to 4 correspond to warning level selection means, and the warning level generation circuit 1 corresponds to warning level generation means, respectively.

(Modification) In the present embodiment, the warning level Vck is divided into three stages, but it may be two stages, four stages or more. The more the warning level Vck is increased, the more accurate battery life warning can be given.

On the other hand, the decoder 11 becomes complicated. Also. In a camera using a microcomputer, the above method can also be performed within the microcomputer. By doing so, the scale of the circuit can be reduced.

Further, although the case has been described in which a lithium battery is used as the power source for the camera, it goes without saying that the invention is not limited to this.

(Effects of the Invention) As described above, according to the present invention, there is provided a counting means for determining the number of shots by weighted counting the number of shots taken after battery loading, a warning level generating means for generating a plurality of warning levels, and A warning level selecting means is provided for selecting a higher value warning level from the warning level generating means as the number of shots by the means increases, so that the warning level can be set according to the temperature characteristics of the battery which changes depending on the temperature conditions at the time of shooting. Since the warning level is set, the number of shots from the time the warning is issued until the operation becomes inoperable is constant regardless of the temperature conditions, and the battery life warning is always accurate. It can be performed.

[Brief explanation of drawings]

FIG. 1 is a block diagram showing an embodiment of the present invention, FIG. 2 is a diagram explaining the relationship between the number of shots and the voltage across the terminals of the battery, and FIG. 3 is a diagram illustrating the relationship between the number of shots and the warning level. The explanatory diagram, Figure i4, is a diagram showing the discharge characteristics of a general lithium battery, and FIG. 5 is a diagram explaining the relationship between the number of shots in a conventional neck-mounted device and the warning level and prohibition level. 1... Warning level generation circuit, 2 to 4...
・Analog switch, 5...Comparator, 6
...warning circuit, 7,8...counter,
9...OR gate, 10...Counter, 11...Decoder, Vck...Warning level, vC5...Prohibition level, N... ...
·number of shots. Patent Applicant Canon Co., Ltd. Representative Minoru Nakamura Figure 1 Figure 3 NI N2 Number of shots N Number of shots N

Claims (1)

[Claims] 1. Comparison means for comparing the voltage between the terminals of the battery and a warning level higher than the prohibition level at which the camera does not operate normally; and the comparison means determines that the voltage between the terminals of the battery is lower than the warning level. In a camera battery life warning device that is equipped with a warning means that issues a warning that the battery life is nearing when a signal indicating that the battery life is near is input, the number of shots is determined by weighted counting of the number of shots taken after the battery is loaded. A counting means, a warning level generating means for generating a plurality of warning levels, and a warning level selecting means for selecting a higher value warning level from the warning level generating means as the number counted by the counting means increases. A camera battery life warning device characterized by: