JPS5933114Y2 - Ionization smoke detector signal processing circuit - Google Patents

Description

[Detailed description of the invention] This invention relates to a signal processing circuit for an ionization type smoke detector using an ion chamber.The purpose of the invention is to constantly monitor direct current and immediately switch to a pulse monitoring state when smoke enters. , the purpose is to eliminate malfunctions due to noise after transitioning to the pulse monitoring state, and other objectives are to provide a signal that can be easily integrated into an IC using a digital counting circuit and has no errors due to voltage or temperature. Another object of the present invention is to obtain a processing circuit, and to improve the detection accuracy by making the time from smoke intrusion to processing the signal and outputting an output constant.

The signal processing circuit of a conventional ionization smoke detector has a switching element 2 connected in series to an ion chamber 1 as shown in Fig. 1, and an oscillation circuit 3 as shown in Fig. 2a.
The smoke detection signal as shown in Figure 2 is amplified by the amplification circuit 4, the output is stored in the storage capacitor C as shown in Figure 2C, and the level detection circuit 5 is used to connect the smoke detection signal to the capacitor. The output circuit 6 detects the voltage level of C and outputs it as shown in Fig. 2d.
I was trying to output output through .

In this case, the capacitor C has a large capacity and the IC
, the number of external components increases and the pulses are accumulated sequentially, so the number of pulses until the level detection circuit 5 operates varies depending on the signal size, and the time from detection to operation is constant. Furthermore, if the pulse interval is lengthened in order to improve the noise resistance performance, there is a drawback that the operating time varies depending on at what point during the pulse-off period smoke enters.

The present invention was devised in view of this point, and will be explained in detail below using actual cases.

In FIG. 3, 1 is an ion chamber, 2 is a switching element, 3 is an oscillation circuit, 4 is an amplification circuit, 5 is a level detection circuit,
Reference numeral 6 represents an output circuit, which is similar to that shown in FIG.

7 is an auxiliary amplification circuit, 8 is a one-shot circuit, and 9 is a counting circuit.

Now, when smoke enters the ion chamber 1, the impedance of a part of the ion chamber increases, and the potential at point a in Figure 3 changes to the 4th point.
The voltage increases as shown in the figure, and this voltage is amplified by the auxiliary amplification circuit T, and when it exceeds a certain level, the oscillation circuit 3 starts oscillating as shown in Figure 4a, and the switching element 2 turns on and off. As a result, a pulse-like smoke detection signal as shown in Fig. 4C appears at point b, and when smoke is present, its peak value rises, and is amplified by the amplification circuit 4, resulting in level detection. The level is detected by the circuit 5, and the one-shot circuit 8 is activated to apply a voltage to the counting circuit 9 via the control element 10 as shown in FIG. 4d.

At the same time, the output of the level detection circuit 5 as shown in FIG. produces output like .

Incidentally, if the output of the auxiliary amplification circuit 7 is used, the one-shot circuit 8 can be omitted since the output of the auxiliary amplification circuit 7 will remain on while the smoke detection signal is present.

In FIG. 5, a flip-flop 11 is used in place of the one-shot circuit 8 in FIG. 3, and the flip-flop 11 is reset by the output of the oscillation circuit 3.

FIG. 6a shows the reset signal waveform.

Similar to the one in Figure 3, when smoke enters the ion chamber 1, the oscillation circuit 3 is activated, and the smoke detection signal is amplified and level detected, and the flip-flop 11 is set by the output as shown in Figure 6. Then, the power of the counting circuit 9 is turned on by the output.

The flip-flop 11 is reset the moment the oscillation circuit 3 outputs an output, but when a smoke detection signal is subsequently generated, the flip-flop 11 is immediately set to the set state.

In this way, while there is a smoke detection signal, the power to the counting circuit 9 is turned on as shown in FIG. 6C.

However, although there is a moment when the switch turns off momentarily, the on state is maintained by connecting the off delay capacitor C2 to the control element 10.

Then, the output of the level detection circuit 5 as shown in FIG. 6d is counted by the counting circuit 9, and when a certain number is reached, the output as shown in FIG. 6e is outputted from the output circuit 6.

In FIG. 7, an accumulation circuit 12 and a second level detection circuit 13 are used in place of the counting circuit 9 of the embodiment shown in FIG.

When smoke enters the ion chamber 1 in the same manner as described above, Fig. 8a
The output of the oscillation circuit 3 as shown in FIG. 8 is obtained, and when the smoke detection signal exceeds a certain level as shown in FIG.
trigger.

Output pulse width Tc of one-shot circuit 8, t≦T≦2t
shall be.

Here, t is the pulse interval of the smoke detection signal.

Therefore, while there is a smoke detection signal, the one-shot circuit 8
As the output, continuous pulses of a constant level are obtained as shown in FIG. 8C.

This voltage is stored in the capacitor of the storage circuit 12 to obtain the output voltage as shown in FIG.
When the detection level of 3 is reached, the output circuit 6 e
Produces output like this.

FIG. 9 shows an example in which an accumulation circuit 12 and a second level detection circuit 13 are used in place of the counting circuit 9 in the actual example shown in FIG.
The output of the flip-flop 11 becomes as shown in FIG. 10C by the reset signal from the oscillation circuit 3 of the flip-flop 11 as shown in FIG. 0A and the set signal from the smoke detection signal as shown in FIG.

This output is accumulated in the accumulation circuit 12, and when it reaches the detection level of the second level detection circuit 13, an output is output from the output circuit 6.

As shown above, the present invention includes an oscillation circuit that starts oscillating when smoke enters the ion chamber, a switch element that applies a pulse voltage to the ion chamber by the output of the oscillation circuit, and a switch element that applies a pulse voltage to the ion chamber by applying the pulse voltage. Since it is equipped with an ion chamber that detects smoke detection signal as a pulse signal, an amplification circuit that amplifies the pulsed smoke detection signal, and a level detection circuit that detects the level of the output of the amplification circuit, DC monitoring is always performed. When smoke enters, you can immediately switch to pulse monitoring state and output if there are multiple inputs, and check whether the operation is due to noise or not.
Malfunctions due to noise can be prevented by determining whether the problem is caused by smoke, and since it is constantly monitored by direct current, there is no delay in starting the operation.Also, the output of the level detection circuit can be used to turn on the power to the counting circuit for a certain period of time. At the same time, since the output of the level detection circuit is counted and the output is output when the number reaches a preset value, a digital counting circuit can be used and it can be easily integrated into an IC, and errors due to voltage and temperature can occur. Furthermore, the output pulse width of the level detection circuit is expanded to be equal to or greater than the pulse period and stored in the storage circuit, and the output is output when the output of the storage circuit reaches a certain level. Therefore, the time required for signal processing and output after smoke intrusion can be made constant, and the detection accuracy can be improved.

[Brief explanation of the drawing]

Fig. 1 is a block circuit diagram of a signal processing circuit of a conventional ionization smoke detector, Fig. 2 a = d is a signal waveform diagram of the same main part as above, Fig. 3 is a block circuit diagram of an embodiment of the present invention, Fourth
Figures a = f are the same main part signal waveform diagrams as above, Figure 5 is a block circuit diagram of another embodiment of the present invention, Figures 6 a "-e are the same main part signal waveform diagrams as above, and Figure 7 is the main part signal waveform diagram of the same as above. A block circuit diagram of another actual case of the invention, FIGS. 8a-e are main part signal waveform diagrams of the same as above,
FIG. 9 is a block circuit diagram of still another embodiment of the present invention, and FIG.・Switching element, 3...Oscillation circuit, 4...Amplification circuit, 5...Level detection circuit, 6...Output circuit, 8... ...One-shot circuit, 9...
... Counting circuit, 10... Control element, 12...
...Storage circuit, 13...Second level detection circuit.

Claims (2)

[Scope of utility model registration request] (1) An oscillation circuit that starts oscillating when smoke enters the ion chamber, a switching element that applies a pulse voltage to the ion chamber using the output of the oscillation circuit, and detects smoke as a pulse signal by applying the pulse voltage. comprising an ion chamber, an amplification circuit that amplifies the pulsed smoke detection signal, and a level detection circuit that detects the level of the output of the amplification circuit,
Turning on the power of a counting circuit for a certain period of time using the output of the level detection circuit, and counting the output of the level detection circuit;
A signal processing circuit for an ionization smoke detector that outputs an output when a preset number is reached. (2) For practical use, the output pulse width of the level detection circuit is expanded to be equal to or greater than the pulse period and stored in the storage circuit, and the output is output when the output of the storage circuit reaches a certain level. A signal processing circuit for an ionization smoke detector according to claim 1.