JPS5814985B2 - Change detection equipment - Google Patents

Description

[Detailed description of the invention] The present invention relates to a change detection device.

For example, a light-beam automatic alarm device detects changes in light emitted from a light-emitting element using a light-receiving element, converts it into electricity, amplifies and detects the signal, and obtains a driving output for an output device such as an alarm. In the case where a change in the light is converted into an electrical signal, the device operates in the same way as when a change in light is detected when the driving power source is turned on or off, resulting in malfunction.

An object of the present invention is to improve the prevention of malfunction in such a change detection device and to ensure reliable change detection.

1 and 2 show the circuit and operation of a conventional change detection device.

In FIG. 1, A is a detector circuit that includes a light receiving element P that converts an optical signal into a detection signal, an amplification, and a detection circuit V, B is an output circuit that includes a voltage detection circuit, a relay circuit, etc., and C is the detector circuit. This is a malfunction prevention circuit connected between power supply line 11.A and output circuit B, respectively. L, connected between.

The detector circuit A includes a detection transistor Tr in its final stage,
and a diode D from its collector.

The transistor T of the malfunction prevention circuit C is connected through the resistor R1.
It is connected to the base of r2.

The transistor Tr1 is off in the steady state of receiving an optical signal, and detects a change when the optical signal is interrupted or changes again, and turns on the transistor Tr when a change occurs. That's what I do.

R2 is a limiting resistor, and L is a display element.

The base of the transistor Tr2 of the malfunction prevention circuit C is biased with a voltage dividing circuit consisting of a capacitor C1, resistors R3, and R4, and the capacitor C1, resistor R3, and diode D2 prevent malfunction when the power is turned on. A signal line 13 extending from the collector of the circuit to the output circuit B through resistors R5 and R6 is provided,
The resistor R5 and the capacitor C2 connected between the power supply line 12 prevent malfunction when the power is turned off.

Note that R7 is the collector resistance of the transistor Tr2.

In the detection operation in the above configuration, even if the detection transistor Tr1 to the detector circuit is turned on due to a delay in the rise of the light-emitting element side circuit when the power is turned on, the transistor Tr1 is turned on until the capacitor C1 is charged.
A current is caused to flow through the base of transistor Tr2 and the transistor Tr2 is turned on for a certain period of time so that no signal is output.

Then, immediately after the power is turned off, the transistor T
Even if r2 is momentarily turned off, no signal is output until capacitor C2 is charged.

In a change detection circuit with a malfunction prevention circuit, the second
As shown in the figure, when the power is turned off and the power supply voltage E gradually decreases until it reaches the change detection level of the detector circuit A, the transistor Tr1 is turned on, the transistor Tr2 is turned off, and the capacitor C2 is charged. It will be done.

When this charging voltage rises, a signal is output to the output circuit B.

In order to prevent malfunction by suppressing the peak value ep of this signal output, the value of capacitor C2 or resistor R6 must be made thicker, so the response speed of change detection during normal operation will be reduced. There are drawbacks such as the fact that it only gets worse.

The present invention has been made in view of the above-mentioned problems and as a countermeasure thereof.

The embodiment of the variation detection circuit of the present invention will be described below with reference to FIGS. 3 and 4, in which the same parts as in FIGS. 1 and 2 showing the conventional example are given the same reference numerals. In one embodiment of the present invention, a malfunction prevention circuit C is connected between the detector circuit A and the output circuit B, and is supplied with power from a power supply line 1112, respectively.

The detector circuit A includes a detection transistor Tr1 at its final stage.
A signal line 13 is extended from its collector to the output circuit B through a diode D1 and a resistor R7, and the signal output is detected to operate the relay of the output circuit B.

The transistor Tr1 is on when the optical signal is in a steady state, detects a change when the optical signal is blocked or changes again, and turns off the transistor Tr1 when a change occurs. It's Nishide.

The malfunction prevention circuit C is a voltage dividing circuit made up of a transistor Tr3 which is arranged in parallel to the transistor Tr1 through a diode D1 and whose collector-emitter is connected between the signal line 13 and the power supply ground line 12, a capacitor C1, and resistors R3 and R4. The circuit is biased, and the resistor R3 and diode D2 prevent malfunction when the power is turned on. Furthermore, a circuit consisting of a resistor R8 and a transistor Tr4 connected between the power supply lines 11 and 12, and voltage dividing resistors R0 and R1o
A constant voltage element ZD is connected to the midpoint between the base of the transistor Tr and the voltage dividing resistors R0 and R1, and the base circuit of the transistor Tr2 is formed from the collector through the diode D3 and the resistor R1.

When the power supply E is connected to the power supply lines 11 and 12, the base current is passed through the transistor Tr3 while the capacitor C1 is being charged, and the transistor Tr3 is turned on. Even if the transistor Tr is in the signal detection state, it cuts the signal line 13, and when the capacitor C rises, the voltage divider circuit including the capacitor C reverse biases the transistor Tr4 and turns off the transistor Tr1.
The signal is detected.

Therefore, the delay time caused by the capacitor C1 is set to be longer than the malfunction time of the detector circuit A during power-on operation, and the detector circuit A is completely turned on by the transistor Tr1.
What is necessary is to set the transistor Tr3 to a reverse bias and turn it off after the transistor Tr3 is turned on.

Then, transistor Tr is turned on, Tr3 is turned off, and Tr
4 enters the normal alert state when it is in the on state.

In the following operation when the power is off, the voltage dividing resistor R9JR1
When the power supply voltage drops below the set voltage determined between 0 and its voltage divider circuit and the constant voltage element ZD connected between the transistor Tr4, the transistor Tr4 is turned off, and the voltage is A current is applied to turn on the transistor Tr3.

Therefore, when the power supply voltage is below a certain value, the signal line 13 is short-circuited to cut the output signal.

In this way, the set voltage at which the transistor Tr4 is turned off is set to a value where the power supply voltage E in FIG. 2 is higher than the voltage E' that causes the detector circuit A to malfunction (thereby, Even if the transistor Tr1 is turned off and outputs a signal, the output signal can be cut by turning on the transistor Tr3 before that.

In normal detection operation, the detector circuit A receives the optical signal, converts it into electricity, turns on the transistor Tr1, and outputs no signal through the signal line 13, but when there is a change in the level of the optical signal. This consists of turning off the transistor Tr1 and sending a signal to the output circuit B. In this case, the malfunction prevention circuit C does not operate.

FIG. 4 shows another embodiment of the present invention, in which a plurality of detector circuits AH2A21A3 are provided.
I, A27A3 are connected to signal lines 13a, 13b, 1 separately.
3c, and diodes D1a,
D, b, and Dlc are used to connect each other to signal line 1.
3 and extend the detector circuit-A12A2. . . . can be driven by the same output circuit B when one of them is activated.

As described above, according to the variation detection circuit of the present invention, when the power is turned on, the voltage divider circuit including the capacitor C1 operates with a delay, and when the power is turned off, the transistor Tr3, which operates below the set voltage, is sent to the output circuit B as a signal. By connecting it to the sending signal line 13 and configuring it to cut the output signal, it not only prevents malfunctions when the power is turned on and off, but also eliminates the influence of the capacitor C2, which is a drawback of the conventional method, when the power is turned off. However, since the output signal is cut as the power supply voltage drops, malfunction prevention is ensured.Since there is no capacitor C2 connected to the signal line 13, the response speed during normal operation is not slowed down, and the performance is stabilized. The detector circuit is like A1゜A2.A3 (
To obtain an improved change detection device in which only one malfunction prevention circuit C is required even when there are a plurality of circuits.

[Brief explanation of drawings]

Figures 1 and 2 show conventional change detection equipment.
The figure is a circuit diagram, and FIG. 2 is a characteristic diagram. 3 and 4 show the change detection device of the present invention, FIG. 3 is a circuit diagram of one embodiment, and FIG. 4 is a circuit diagram of another embodiment. A...Detector circuit, B...Output circuit,
C... Malfunction prevention circuit, Trl, Tr3. Tr
4...Transistor, 11,12...
Power line, 13...Signal line, C...
・Capacitor, ZD... Constant voltage element.

Claims (1)

[Claims] 1. A change detection device that includes a detector circuit that converts a change in light into an electrical signal and detects it, and a change detection device that receives the detection signal as an input and has an output circuit, together with a detection transistor that operates according to the detection signal, A transistor for on-operation control is provided that is connected to a voltage divider circuit including a capacitor and that extends from the detection transistor for a certain period of time when the power is turned on to a non-detecting state, and an off-operation control that detects a drop in the power supply voltage. A malfunction prevention circuit that includes a transistor for controlling the off operation and controls the transistor for controlling the on operation after the power is turned off by the transistor for controlling the off operation to put the signal line in a non-detecting state and cut off the output signal immediately after the power is turned on and off. A change detection device characterized by being provided between a detector circuit and an output circuit.