JPS5844475Y2 - Dead battery indicator circuit for battery-powered smoke detector - Google Patents

Description

[Detailed Description of the Invention] The present invention relates to a dead battery indicating circuit for a battery-powered smoke detector.

As shown in FIG. 1, the battery-depleted battery indicator circuit 9 of a conventional battery-powered smoke detector is turned on and off by means of an oscillation circuit 2 that blinks the light-emitting element 1 of the smoke sensor and an oscillation output, causing the display element 3 to blink and turn on. At the same time, the voltage of the battery power source 4 is detected, and as shown in Fig. 2a
If the battery voltage is below the high detection level L1 set by the level shift circuit 5 as shown in FIG. It is possible to turn off the display element 3 as shown in Fig. 2e and to intermittently drive the sounding element 8, such as a buzzer, as shown in Fig. 2d, to indicate that the battery is exhausted by making a sound and turning off the display light. It is possible.

In addition, when the battery cannot be replaced immediately, such as at night, the switch SW is changed (FIG. 2C), and the level shift circuit 5 lowers the detection level of the dead battery detection circuit 9 to the low level L2. The detection by the disconnection detection circuit 9 indicates that the battery is normal, and the sounding of the sound generating element 8 can be stopped.

By the way, in the conventional circuit, by switching the detection level of the level shift circuit 5, the dead battery detection circuit 9 detects that the battery voltage is normal, so the display stop circuit 6 returns to the state shown in FIG.
Since the display element 3 starts blinking again as shown in FIG. 2, there is a problem in that it causes a misunderstanding that the battery power source 4 is normal and makes the user forget to replace the battery power source 4 with a new one.

The present invention was developed in view of these shortcomings, and its purpose is to provide a normal display by blinking the display element when the battery power is normal, and to turn off the display element and ring the sounding element when the battery runs out. To provide a dead battery display circuit for a battery-powered smoke detector, which can stop the sounding of a sounding element while continuously displaying a display element's light-off state while maintaining the detection ability of a smoke sensor.

The present invention will be explained below with reference to examples.

FIG. 3 shows a rotation block diagram of one embodiment.

The smoke sensor is constructed by connecting a light emitting element 1 such as a light emitting diode in series to a transistor 10 which is turned on and off by the oscillation output of an oscillation circuit 20 to constantly flash and emit light. When the scattered light from the light emitting element 1 caused by smoke When the detection signal exceeds a certain level, the detection signal is output and held from the holding circuit 14,
A transistor 5 connected to a battery power source 4 through a sounding element 8 such as a buzzer is turned on to cause the sounding element 8 to continuously sound, thereby issuing an alarm.

Note that the holding circuit 14 is reset by the oscillation output of the oscillation circuit 2.

On the other hand, the dead battery display circuit section includes a dead battery detection circuit 9 which is turned on and off by the oscillation output of the oscillation circuit 2, lights up the display element 3 made of a light emitting diode during operation, and checks the voltage of the battery power source 4; A display stop circuit 9 turns on the display element 3 when a dead battery detection signal is input from the dead battery detection circuit 9, and a display stop circuit 9 operates to turn on/off and drive the transistor 15 when a dead battery detection signal is input from the dead battery detection circuit 9. The button is composed of a notification sound circuit 7 consisting of an oscillation circuit and a level shift circuit 5 that switches the detection level of the dead battery detection circuit 9 between high and low, and the detection level of the dead battery detection circuit 9 is the normal level. Shift 4-way 5 switch SW.

By turning on, the high level L is set.

The switch SW1 is interlocked with the switch SWo inserted in series in the energizing circuit of the display element 30. When the switch SW is turned on, the switch SWo is turned off, and conversely, the switch SW1 is turned on.
When switch 1 is turned off, switch 1% is turned on.

Next, the operation of the dead battery display circuit section will be explained using the specific circuit shown in FIG.

Then, the transistor 6 of the dead battery detection circuit 9, which is connected in parallel to the battery power source 4 through the series circuit of resistors R1 to R3 of the level shift circuit 5, performs on/off operation by the oscillation output of the oscillation circuit 2. conduct, resistors R1, R2 and R
The battery dead detection circuit 9 compares the voltage divided by the voltage dividing circuit with the reference voltage and the transistor 16 when the battery is normal.
When the transistor 17 of the display stop circuit 6 is turned on, a signal is output that turns on the transistor 17 of the display stop circuit 6.

By turning on this transistor 110, the transistor 18
is turned on, and at this time, the display element 3 has a switch SWo.
Electric current flows through it and it emits light.

Therefore, in synchronization with the oscillation signal of the oscillation circuit 2, the battery exhaustion detection circuit 9 and the display stop circuit 6 are turned on and off to cause the display element 3 to blink as shown in section A in FIG. 5F.

Next, when the voltage of the battery power supply 4 becomes low and the input voltage of the dead battery detection circuit 90 becomes lower than the detection level L1 as shown in FIG. A detection signal for turning off the transistor 7 is output as shown in FIG.

Therefore, the display stop circuit 6 continues to be in the OFF state, and the display element 4 is turned off as shown in the section f in FIG. 5 to indicate that the electric power is cut off.

At the same time, the transistor 18 of the display stop circuit 6 functions as a control element for the notification sound circuit 7, and as the transistor 1B continues to turn off, the notification sound circuit 7 is controlled by the programmable unijunction transistor PUT with a time constant determined by the capacitor C1 and the resistor R4. is turned on and off, and in synchronization with this on and off, the notification sound circuit 7 turns the transistor 5 on and off, causing the sound generating element 8 to make intermittent sounds as shown in FIG. 5d.

If there is a case where the battery cannot be replaced immediately, the sound of the sound generating element 8 becomes a nuisance.

When the power is off, switch SW1 is turned on to shift the level as shown in Fig. 5C, and the resistance R of the level shift circuit 5
2 is short-circuited, and the detection level of the dead battery detection circuit 9 is set to the fifth level.
It will be set to a low level L2 as shown in Figure a,
The output signal of the dead battery detection circuit 9 is the same as when the battery is normal.

Therefore, since the transistors γ and 18 of the power failure detection circuit 6 repeat on and off, the capacitor C1 of the notification sound circuit 7 is a programmable unijunction transistor PUT.
The potential that triggers the transistor 5 is not charged and does not turn on the transistor 5.

As a result, the sound generating element 8 does not vibrate and becomes silent.

On the other hand, since the switch SWo is turned on in conjunction with the turning on of the switch SW, even if the transistor 5 is turned on, the display element 3
No current flows through the battery, and the indicator continues to indicate that the battery is dead by turning off the light.

FIG. 5e shows a time chart of the switch SWo.

The present invention is configured as described above, and a switch is added to cut off the energization circuit of the display element when the detection level of the dead battery detection circuit is set to a low level by the level shift circuit. If it is desired to stop the sounding element from ringing, this can be achieved without stopping the detection ability of the smoke sensor by lowering the detection level of the dead battery detection circuit using a level shift circuit, and in addition, the above switch can cut off the power to the display element. Therefore, even if the sound generating element is silent, the display element can be kept in an off state to indicate that the battery is exhausted, which has the advantage of preventing forgetting to replace the battery.

[Brief explanation of the drawing]

Fig. 1 is a circuit block diagram of the conventional example, Fig. 2 is a time chart for explaining the operation of the same as above, Fig. 3 is a circuit block diagram of an embodiment of the present invention, and Fig. 4 is an indicator of dead battery in the same as above. A specific circuit diagram of the circuit section, and FIG. 5 is a time chart for explaining the operation of the same as above, where 2 is an oscillation circuit, 3 is a display element, 4 is a battery power source, 5 is a level shift circuit, and 6 is a display stop circuit. , 7 is a notification sound circuit, 8 is a sound generating element, 9 is a dead battery detection circuit, and SWo is a switch.

Claims (1)

[Scope of utility model registration request] A dead battery detection circuit that detects when the voltage of the battery power supply reaches the detection level, a display element that blinks and emits light in synchronization with the signal from the oscillation circuit of the smoke detector, and a display element that detects when the battery power supply voltage reaches the detection level. A battery-operated device equipped with a display stop circuit that turns off the light, a notification sound circuit that makes a sounding element sound in response to a detection signal from a dead battery detection circuit, and a level shift circuit that can switch the detection level of the dead battery detection circuit between high and low. A dead battery indicator for a battery-powered smoke detector, which includes a switch that cuts off the energizing circuit of the display element when the detection level of the dead battery detection circuit is set to a low level using a level shift circuit. circuit.