JPS59878B2 - sensor - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a smoke, temperature, etc. sensor activated by a pulse signal.

In conventional sensors of this type, the duty ratio of the pulse signal is made small in order to further reduce current consumption, and an alarm is issued once an abnormality is detected when the pulse signal is on.

Therefore, there was a risk that an alarm would be erroneously issued due to malfunction.

It is an object of the present invention to provide a novel sensor that eliminates these drawbacks.

An embodiment of the present invention will be described below with reference to the drawings.

1 is an oscillation circuit that oscillates a pulse with a long period and a small duty ratio, 2 is a light emitting circuit that emits light in synchronization with this pulse, 3 is a light receiving circuit opposite to this light emitting circuit 2, 4 is an amplifier, and 5 is a light receiving state. 6 is an abnormal signal generation circuit for generating an abnormal signal pulse when detecting an abnormality caused by the level detecting portion 5ζ, 7 is a count circuit, and 8 is this count circuit. An alarm unit issues an alarm after a predetermined number of pulse signals are counted by circuit 7, 9 is a pulse stretching circuit, and 10 is a switching circuit.

Therefore, as shown in Figure 3, the oscillation circuit 1 has a predetermined period T.
1 pulse A is oscillated, the light emitting circuit 2 is driven by the pulse, and an optical pulse signal is sent from the light emitting circuit 2. If an abnormality occurs as shown in B, the connection between the light emitting circuit 2 and the light receiving circuit 3 will be interrupted. Smoke enters between the two, and the amount of light received by the light receiving circuit 3 decreases.

First, when the amount of pulsed light received by the pulse signal a1 falls below a predetermined value, the level detection section 5 causes the abnormal signal generation circuit 6 to generate a pulse C1.

When pulse C1 occurs, pulse C0 is stretched by pulse stretching circuit 9 for a time approximately equal to time T2 in FIG.

The output from the pulse stretching circuit 9 makes the transistor Q of the switching circuit 10 shown in FIG. Change to a small oscillation time constant circuit.

Therefore, the oscillation circuit 1 generates a pulse a2 delayed by a time T2 shorter than <al, as shown in A of FIG.

At this time, if the abnormality continues, the level detection section 5 detects the abnormality and causes the abnormality signal generation circuit 6 to generate a pulse C2 as described above.

This pulse C2 is further stretched by the pulse stretching circuit to reduce the oscillation time constant of the oscillation circuit 1, so that the oscillation circuit 1 generates the pulse a3 after time T2.

Similarly, the oscillation circuit 1 oscillates pulses with a short period T2 while an abnormality occurs.

If the abnormal state is resolved midway through, the pulse C from the abnormal signal generation circuit disappears from that point on, and the transistor Q1 of the switching circuit returns to the non-conducting state, so the pulse period of the oscillation circuit 1 returns to its original long period. Return to T1.

After time t1 when the counting circuit 7 counts four pulses C, the alarm section 8 is activated as shown by E.

On the other hand, as shown in FIG. 4, in the case where the oscillation circuit 1 oscillates a pulse F whose period does not change, it is necessary to count four pulses H for which an abnormality is detected after the occurrence of an abnormality G. It takes a longer time t2 than the above time t1.

In addition, if the count is not performed, an alarm is immediately activated as shown by (■), and a malfunction is likely to occur due to dust or the like.

Next, the above embodiments of the present invention will be explained based on actual numerical examples.

In the sensor shown in Fig. 1, in a normal state, the light emitting circuit 2
For example, when an abnormality is detected while outputting a -1-second optical pulse signal at 300 second intervals, the oscillation time constant of the oscillation circuit changes, and for example, the abnormal signal at 3 second intervals becomes abnormal. It is output from the signal generation circuit 6.

For this reason, for example, when issuing an alarm by counting 5 pulses from the abnormal signal generation circuit, 5 pulses of the abnormal signal will be counted in approximately 15 seconds, compared to approximately 150 seconds when the pulse cycle is not changed. It has the advantage that the time required can be significantly shortened, and the alarm operation of the alarm unit 8 can be performed extremely quickly and with high reliability.

In addition, under normal conditions, for example, 300 second intervals,
When outputting a 0.001 second optical pulse signal and when outputting a 0.001 second optical pulse signal at 1 second intervals (
As in Section 2)-3, since the power consumption during normal 30 seconds can be minimized as much as possible, it can also be applied to simple battery-powered fire detectors for home use.

In this way, a sensor with low power consumption can be achieved, especially when a large number of two-wire sensors are connected in parallel to a sensor circuit, and each sensor is detected by the operation of a relay. A unique advantage is that the lower the power consumption on each side, the more sensors can be connected to the sensor circuit.

In other words, the sensor according to the present invention as described above consumes very little current because it uses long-cycle pulses with a small duty ratio during normal times, and after detecting an abnormality, it uses short-cycle pulses. Since the alarm is issued after confirming the continuation of the abnormality and counting a predetermined number of these short-period pulses, there is no possibility that the alarm will be activated erroneously due to dust or the like.

Moreover, when an alarm is triggered by this count, the oscillation pulse is converted from a long cycle to a short cycle, so even though long cycle pulses are normally used, the alarm is activated quickly, and As soon as the abnormal condition is resolved, the tube returns to its original long-period pulse, which has various effects.

[Brief explanation of the drawing]

Fig. 1 is a system diagram of a sensor showing one embodiment of the present invention;
3 is a waveform diagram showing the operation of an embodiment of the present invention, and FIG. 4 is a waveform diagram showing the operation of a conventional device. 1... Oscillation circuit, 2... Light emitting circuit, 3
...Photodetector circuit, 4...Amplifier, 5...
... Level detection section, 6 ... Abnormal signal generation circuit, 7 ... Count circuit, 8 ... Alarm section, 9 ... Pulse extension circuit , 10...
...Switching circuit.

Claims (1)

[Claims] 1. An oscillation circuit that oscillates pulses with a long period and a small duty ratio, an oscillation section driven by the oscillation circuit output pulses, a level detection section that receives pulse signals from the oscillation section and detects abnormalities, and an abnormal signal generating circuit that is activated by the level detection section and generates a pulse in the event of an abnormality; a switching circuit that is activated by the pulse from the abnormal signal generating circuit and changes the oscillation cycle of the oscillation circuit to a short period; and the abnormal signal generating circuit. A sensor consisting of a counting circuit that counts the number of pulses, and an alarm section that operates an alarm when the counting circuit counts a predetermined number of pulses.