JPS5830638B2 - Signal processing circuit for photoelectric smoke detector - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a signal processing circuit for a photoelectric smoke detector, and relates to a signal processing circuit for a photoelectric smoke detector, in which a delay circuit is provided in a pulse output circuit in a photoelectric smoke detector having a pulse lighting detection light source. That is.

The signal processing circuit of conventional photoelectric smoke detectors does not have a delay circuit, so false alarms may be generated due to flashes, electrical noise, insects flying in the detection area, etc. There were disadvantages such as difficulty in

From this point of view, the present invention amplifies the optical signal detected by the light receiving element that receives the scattered light in the burning chamber with an amplifier, and sends one of the outputs of the amplifier through a pulse width extension circuit. The other output of the amplifier is led to the charging circuit to charge the capacitor, and the other output of the amplifier is led to the AND circuit via the NOT circuit.The oscillation circuit that pulse-drives the light source in the incinerator is also led to the AND circuit, and the output of the AND circuit is led to the AND circuit. The output is led to a discharge circuit via a pulse width extension circuit to discharge the charge in the capacitor, and the level detection circuit determines the charging voltage of the capacitor, and outputs when it reaches a certain level. be.

DESCRIPTION OF THE PREFERRED EMBODIMENTS A signal processing circuit for a photoelectric smoke detector according to the present invention will be specifically described below with reference to the drawings.

Reference numeral 1 denotes a smoke chamber, in which a light source 2 consisting of a light emitting diode and a light receiving element 3 consisting of a solar cell are installed.

Reference numeral 4 denotes an amplifier for amplifying the optical signal detected by the light receiving element 3, and one of the outputs of the amplifier is led to a charging circuit 6 via a pulse width extension circuit 5 to charge a capacitor 7. The other output of the amplifier is led to an AND circuit 9 via a NOT circuit 8.

Reference numeral 10 denotes an oscillation circuit that pulse-drives the light source 2 in the baking chamber 1. The oscillation circuit 10 is also led to an AND circuit 9, and the output of the AND circuit 9 is sent to a discharge circuit 12 via a pulse width extension circuit 11. This is to discharge the charge in the capacitor 7.

13 is a level detection circuit for detecting the level of the charging voltage of the capacitor 7; 14 is an output; and 15 is a DC power supply.

Next, the operating state of the present invention will be described.

In the absence of smoke, there is no output from the amplifier 4, so the charging circuit 6 is in an off state, and both the NOT circuit and the oscillation circuit 10 output, and the AND output 9 causes the pulse width extension circuit 11 to output. Since the discharging operation is repeated according to the width, the capacitor 7 is not charged.

Now, when a fire breaks out and smoke flows into the roasting chamber 1, the light from the light source 2 is diffusely reflected by the smoke and the light receiving element 3 outputs an output. As soon as the charging circuit 6 is turned on, the output of the NOT circuit 8 disappears,
Therefore, the output of the AND circuit 9 becomes zero and the discharge circuit 12 is turned off.

In this way, pulse discharge is performed in response to the pulse from the oscillation circuit 10 over a period of 50 hours in the pulse width extension circuit, and the charging of the capacitor 7 progresses step by step.
The charging operation is performed in several pulses determined by the capacity of the battery and the charging time constant.

Then, the charging voltage reaches the detection level of the level detection circuit 13, and an output 14 is produced.

If noise were to arrive at this moment, charging would be completed with one pulse, and the battery would be discharged immediately with the next pulse.

The second time chart shows the above operating status.
It is a diagram.

As described above, the present invention amplifies the optical signal detected by the light receiving element that receives scattered light inside the smoke chamber using an amplifier, and sends one of the outputs of the amplifier to the charging circuit via the knowless width extension circuit. The other output of the amplifier is led to the AND circuit via the NOT circuit, and the oscillation circuit that pulses and drives the light source in the smoke chamber is also led to the AND circuit, and the output of the AND circuit is The charge in the capacitor is discharged by guiding it through a pulse width extension circuit to a discharging circuit, and the level detection circuit determines the charging voltage of the capacitor, and when it reaches a certain level, it outputs an output. It has the advantage of eliminating false alarms caused by instantaneous noise caused by electrical noise, insects flying in the detection area, etc.

[Brief explanation of the drawing]

Figure 1 is an electrical circuit diagram of the signal processing circuit of a photoelectric smoke detector.
FIG. 2 is a time chart showing the operating state of the same as above. 1 is a baking chamber, 2 is a light source, 3 is a light receiving element, 4 is an amplifier, 5,
11 is a pulse width extension circuit, 6 is a charging circuit, 7 is a capacitor, 8 is a NOT circuit, 9 is an AND circuit, 10 is an oscillation circuit, 12 is a discharge circuit, 13 is a level detection circuit, 14 is an output, 15 is a DC power supply.

Claims (1)

[Claims] 1 Amplify the optical signal detected by the light receiving element that receives the scattered light inside the burning chamber with an amplifier, and lead one of the outputs of the amplifier to the charging circuit via the pulse width extension circuit to charge the capacitor. At the same time, the other output of the amplifier is led to the AND circuit via the NOT circuit, and the oscillation circuit that pulse-drives the light source in the firing chamber is also led to the AND circuit, and the output of the AND circuit is sent to the pulse width extension circuit. Signal processing for a photoelectric smoke detector characterized in that the charge in the capacitor is discharged by guiding the capacitor through the discharge circuit, and the charge voltage of the capacitor is determined by a level detection circuit, and an output is output when a certain level is reached. circuit.