JP4150946B2 - Gas leak alarm - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a gas leak alarm having a voltage alarm output function, and more particularly to a gas leak alarm capable of notifying an abnormality of a microcomputer (also simply referred to as a microcomputer) used in its control unit.
[0002]
[Prior art]
FIG. 5 shows a conventional example.
In the figure, 1 is a microcomputer control unit, 2 is a power supply unit, 3 is a gas sensor unit, 4 is a voltage output circuit, 5 is a differentiation circuit, and 6 is a watchdog timer (WDT).
That is, the microcomputer control unit 1 receives the detection signal from the gas sensor unit 3 and instructs the voltage output circuit 4 according to the detection state, for example, a 6V output instruction when no gas is detected (standby or normal), A 12V output instruction is output when city gas or LPG or other raw gas is detected, and an 18V output instruction is output when incomplete combustion (CO) is detected. As the voltage output circuit 4, for example, a constant voltage circuit with variable output voltage such as a series regulator or a power source can be used.
On the other hand, the watchdog timer (WDT) 6 continues to issue a WDT clear signal periodically, and continues resetting so that the WDT 6 does not time out by the signal pulsed by the differentiation circuit 5. When the WDT 6 times out, the microcomputer control unit 1 is reset as an abnormality.
[0003]
[Problems to be solved by the invention]
In the above system, if the microcomputer control unit 1 becomes inoperable due to a component failure or the like, the output voltage of the voltage output circuit 4 becomes unstable, so that it is difficult to detect an abnormality of the alarm device from the outside. There is a problem of becoming.
Accordingly, an object of the present invention is to make it possible to detect an abnormality of an alarm device from outside.
[0004]
[Means for Solving the Problems]
In order to solve such a problem, in the invention of claim 1, in a gas leak alarm device having a voltage alarm output function for outputting different voltages according to gas non-detection, raw gas detection or incomplete combustion state, respectively. A microcomputer, a watchdog timer clear signal periodically output from the microcomputer, and a watchdog timer that outputs a reset signal to the microcomputer when the microcomputer runs away or stops, and the watchdog timer clear And a timer that outputs a time-up output when a predetermined time has elapsed, and is set to an abnormal output state by the time-up output. It is characterized by that.
[0006]
DETAILED DESCRIPTION OF THE INVENTION
FIG. 1 is a block diagram showing a first embodiment of the present invention.
As can be seen from the figure, the timer circuit 7 is provided in the conventional example shown in FIG. The timer circuit 7 is continuously reset by the WDT clear signal output from the microcomputer control unit 1 as long as the microcomputer control unit 1 is normal.
[0007]
1 will be described with reference to FIG.
If the WDT clear signal is stopped due to an abnormal operation that the microcomputer control unit 1 cannot restart, the WDT 6 times out after a predetermined time longer than the WDT clear output interval, and outputs a pulse as a WDT output. This pulse signal is input to the timer circuit 7 as a start signal, whereby the timer circuit 7 is started, and after a predetermined time longer than the WDT output interval indicated by (4) in FIG. 2, a time as shown in FIG. An up signal is output. This time-up signal continues until the timer circuit 7 is reset, and the output voltage of the voltage output circuit 4 is set to a specified abnormal output level lower than the normal output level, for example, as shown in FIG. The voltage output circuit 4 ignores the output voltage instruction from the microcomputer controller 1 when an abnormal signal is input, and is controlled to an abnormal output level.
[0008]
Thereafter, when the microcomputer control unit 1 is restarted for some reason, the generation of the WDT clear signal is resumed, so that the WDT is reset and the microcomputer control unit 1 starts normal operation. At the same time, the timer circuit 7 is reset and the time-up output shown in FIG. 2 (5) disappears, whereby the output voltage control of the voltage output circuit 4 is switched to the microcomputer control unit 1 side.
At the time of an abnormal operation not caused by a component failure such as a program runaway, the microcomputer control unit 1 is reset by the first WDT output. However, the microcomputer control unit 1 returns to normal operation by restarting, so that the timer circuit 7 is timed up. Therefore, the voltage output circuit 4 does not output an abnormal output level.
[0009]
FIG. 3 is a block diagram showing a second embodiment of the present invention, and FIG. 4 is a diagram for explaining the operation thereof. FIG. 3 is obtained by replacing the timer circuit 7 of FIG. 1 with a counter circuit 8, and the operation is only different as follows.
That is, when a WDT output pulse as shown in FIG. 4 (4) is generated due to an abnormality in the microcomputer control unit 1, the counter circuit 8 counts this pulse as shown in FIG. A count-up signal is generated as in 6 ▼. This count-up signal is input to the voltage output circuit 4 as an abnormal signal, and the output voltage is set to a specified abnormal output level different from the normal output level as shown in FIG.
[0010]
【The invention's effect】
According to the present invention, the watchdog timer output is monitored, and when the watchdog timer output continues for a predetermined period or a predetermined number of pulses, the voltage alarm output is set to an abnormal output state to cause gas leakage to an external device. It is possible to notify the abnormality of the alarm device, and there is an advantage that maintenance such as quick replacement of the alarm device becomes possible.
[Brief description of the drawings]
FIG. 1 is a configuration diagram showing a first embodiment of the present invention;
FIG. 2 is an operation explanatory diagram of FIG. 1;
FIG. 3 is a block diagram showing a second embodiment of the present invention.
4 is an operation explanatory diagram of FIG. 3; FIG.
FIG. 5 is a block diagram showing a conventional example.
[Explanation of symbols]
DESCRIPTION OF SYMBOLS 1 ... Microcomputer control part, 2 ... Power supply part, 3 ... Gas sensor part, 4 ... Voltage output circuit, 5 ... Differentiation circuit, 6 ... Watchdog timer (WDT), 7 ... Timer circuit, 8 ... Counter circuit.

Claims (1)

In a gas leak alarm device with a voltage alarm output function that outputs different voltages depending on gas non-detection, raw gas detection or incomplete combustion state,
A microcomputer, a watchdog timer clear signal periodically output from the microcomputer, a watchdog timer that outputs a reset signal to the microcomputer when the microcomputer runs away or stops, and the watchdog timer clear signal And a timer that outputs a time-up output when a predetermined time elapses, and sets the voltage alarm output to an abnormal output state by the time-up output. Gas leak alarm characterized by.

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