JPH07152428A - Abnormality detecting method for control output device - Google Patents

Abstract

PURPOSE:To quickly and automatically detect that an output signal is in a state different from control output so that a user can be informed of it by issuing a control signal to stop the sending of the output signal in the case that the output signal is in the state different from the control output. CONSTITUTION:An output unit 16A receives the control output A from a CPU 11A and outputs the output signal B for a device to be controlled. This output unit 16A is provided with a comparator to compare detection voltage to be generated in accordance with the output signal B with reference voltage and generate a comparison signal. Comaparator output C is supplied to the abnormality detecting input port of the CPU 11A. When the CPU 11A detects the abnormality of the output unit 16A through prescribed procedure, the CPU 11A informs the user of the abnormality by turning on or flickering an output unit abnormality monitor 18. Thus, even in the case that the transistor, etc., of the output unit 16A is deteriorated or broken, an accident such as the breakdown of the device to be controlled and a fire, etc., can be prevented beforehand.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for detecting an abnormality in a control output device which sends an output signal to control a controlled device.

[0002]

2. Description of the Related Art FIG. 5 is a block diagram of a system in which a furnace is used as a controlled device and a temperature controller for controlling the temperature of the furnace is used as a control output device. In FIG. 5, 1 is a temperature controller, 2 is a furnace, HT is a heater installed in the furnace, SN is a temperature sensor that detects the temperature of the furnace and feeds it back to the temperature controller 1 as a temperature signal input. is there.
3 is an AC power supply for supplying electric power to the furnace 2, 4 is a temperature controller 1
It is a large-capacity SSR that controls the current flowing through the heater HT by an output signal from the.

The inside of the temperature controller 1 has the following structure. That is, 11 is a CPU that controls the temperature controller 1, and 12 is a signal input circuit that processes the temperature input signal from the temperature sensor SN. A / D 13 converts an analog signal output from the signal input circuit 12 into temperature data of a digital signal and supplies the temperature data to the CPU 11.
It is a conversion circuit. Reference numeral 14 is a display circuit for displaying the current temperature, set temperature, etc., and 15 is a key matrix circuit for scanning and inputting a key input from the operation unit.

Reference numeral 16 denotes an output unit which receives a control output A from the CPU 11 and sends an output signal B to the large capacity SSR 4, which can be detached from the temperature controller 1 and freely replaced. Reference numeral 17 is a power supply circuit which receives a supply of an AC power supply to generate a constant DC voltage and supplies it to each unit.

FIG. 6 is a diagram showing an internal circuit of the output unit 16. In FIG. 6, Tr1 is a level shift transistor for converting the level of the control output A from the CPU 11. Tr2 is an output transistor that conducts the current of the output signal B when turned on. Tr3 is a transistor T
It is a protective transistor that prevents the destruction of r2.

Next, the operation of the output unit 16 will be described. Now, when the low-level control output A is input from the CPU 11, the transistor Tr1 is turned on, a current is supplied from the 5V power source to the base of the transistor Tr2, and the transistor Tr2 is turned on. Then, from the 12V power supply to the choke coil L1, a load (not shown), the choke coil L
2. Between the collector and emitter of transistor Tr2, resistor R
The output signal current flows through the path of d. For example, when a trouble occurs on the load side and the choke coil L1 and the choke coil L2 are short-circuited or overloaded, a large current flows between the collector and the emitter of the transistor Tr2 to cause the transistor Tr2 to pass through. It will be destroyed.
Since the rating of this output unit 16 is 12V 20mA, when the current exceeds the value of 20mA, the resistance R
The transistor Tr3 is turned on by the voltage drop of d, the base of the transistor Tr2 is shorted to the ground, and the transistor Tr2 is turned off.

Further, even when the transistor Tr2 and other parts are destroyed by a large current or the like, the output unit 16
The system can be maintained by exchanging itself.

[0008]

However, the transistor of the output unit may be deteriorated or destroyed due to incorrect wiring or external surge during operation. In such a case, in the above-mentioned conventional temperature controller, it takes a lot of time to investigate the cause. In the meantime, if the temperature of the furnace is in an elevated state, there is a problem that the furnace itself may be destroyed or an accident such as a fire may occur.

The present invention solves such a conventional problem. Even when a transistor or the like of the output unit is deteriorated or destroyed, it is promptly and automatically detected to notify the user, An object of the present invention is to provide a method for detecting an abnormality in a control output device such as a temperature controller that prevents accidents such as destruction of the furnace itself and fire.

[0010]

In order to achieve the above object, the present invention compares a detection voltage generated according to an output signal with a reference voltage to generate a comparison signal, and sends the output signal. And a control means for issuing a control output to
The control means may issue a control output for stopping the output of the output signal when the comparison signal has a predetermined value.

[0011]

According to the present invention, with the above configuration, when the output signal is detected in a different state from the control output as a result of the detection, the control output for suspending the output of the output signal is promptly issued. In addition, this is automatically detected and notified to the user, and accidents such as destruction of the controlled device itself and fire are prevented in advance.

[0012]

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

FIG. 1 is a block diagram of a temperature controller to which an abnormality detecting method for a control output device according to the present invention is applied. In this figure, the same components as those of the conventional example shown in FIG. 5 are designated by the same reference numerals, and the description thereof will be omitted. In FIG. 1, 11
A is a CPU as a control means for controlling the temperature controller. The CPU 11A is provided with an input port for abnormality detection. 16A is an output unit that receives a control output A from the CPU 11A and sends an output signal to a furnace (not shown) that is a controlled device.
In addition to the output signal for adjusting the temperature of the furnace, a comparator output C (which will be described later) is sent from the output unit 16A and is supplied to the abnormality detecting input port of the CPU 11A.

Reference numeral 18 denotes an output unit abnormality monitor which lights up or blinks when the output unit 16 becomes abnormal.

FIG. 2 is an internal circuit diagram of the output unit 16A. Also in this figure, the same components as those of the conventional output unit shown in FIG. 6 are denoted by the same reference numerals, and the description thereof will be omitted. 2, in addition to the configuration of the conventional example of FIG. 6, 12V is a predetermined fixed voltage (this is referred to as a reference voltage).
The voltage dividing resistors R1 and R2 for dividing the voltage into a voltage and the comparator CP, which is a comparison means for comparing the reference voltage with the emitter voltage of the transistor Tr2 (this is called a detection voltage), are newly added. The comparator output C, which is the comparison signal from the comparator CP, is supplied to the CPU 11A. That is, when the reference voltage is higher than the detection voltage, a low level signal is supplied to the comparator output C, and when the reference voltage is lower than the detection voltage, a high level signal is supplied to the comparator output C to the CPU 11A.

In this case, the load current on the furnace side, which is the load of the output unit 16A, is set to 10 mA. If the resistance value of the emitter resistance Rd of the transistor Tr2 is 10Ω,
Resistance R when the output current of the output unit 16A is 1 mA
The voltage of d, that is, the detection voltage is 10 mV. Here, the values of the voltage dividing resistors R1 and R2 are determined so that the reference voltage becomes slightly smaller than 10 mV. Therefore, the CPU 11
When the control output from A is 0% (5V), the transistor Tr2 is turned off, the detection voltage becomes 0V, and the comparator output C becomes low level. On the other hand, CPU 11A
When the control output is set to 100% (0 V), the transistor Tr2 is turned on, the detection voltage becomes 100 mV, and the comparator output C becomes high level.

Now, assuming that the transistor Tr2 is opened due to the surge, when the control output from the CPU 11A is 100% (0 V), the detection voltage across the resistor Rd is originally 100 mV, but the transistor Tr2 is open. Therefore, it remains 0V, and the comparator output C is at a low level.

When the transistor Tr2 is short-circuited due to a surge, the detection voltage is 100 mV when the control output from the CPU 11A is 0% (5 V), and the comparator output C is originally at a low level.
It becomes a high level.

FIG. 3 is a flowchart of the CPU 11A showing the operation of detecting an abnormality in the output unit 16A.
The CPU performs a port search (step S1) and determines whether the port is at high level (step S2). When the port is high level, the control output at that time is 10
It is determined whether it is 0% (step S3), and if it is 100%, the output unit is normal. When the control output is 0%, it is determined that the output unit is abnormal and the output transistor is short-circuited.

When the port is at the low level, it is judged whether the control output is 0% (step S4). When it is 0%, the output unit is normal. When the control output is 100%, it is determined that the output unit is abnormal and the output transistor is open or the load is not connected.

FIG. 4 is a view showing the display panel of the temperature controller 1. The display panel is provided with the output unit abnormality monitor 18 described above. Further, 21 is a current temperature display section for displaying the current temperature, and 22 is a set temperature display section for displaying the set temperature. Other than this, this display panel has a level switching key, a mode key, etc., but since they are not related to the present invention, their explanation is omitted.

When the CPU 11A detects the abnormality of the output unit 16A by the above procedure, the output unit abnormality monitor 18 is turned on or blinks to notify the user of the abnormality. Alternatively, instead of the output unit abnormality monitor 18, the entire present temperature display section 21 or set temperature display section 22 can be made to blink.

In the above embodiment, the temperature controller is described as an example of the control output device, but the present invention is not limited to the temperature controller and sends an output signal to control the controlled device. It can be widely applied to detect abnormalities in control output devices.

[0024]

As is apparent from the above-described embodiments, the present invention provides a comparison means for comparing a detection voltage generated according to an output signal with a reference voltage to generate a comparison signal, and a control for sending the output signal. When the output signal is in a state different from the control output as a result of detecting the state of the output signal, the control means for emitting the output is provided to promptly and immediately This is automatically detected and notified to the user, and accidents such as destruction of the controlled device itself and fire are prevented.

[Brief description of drawings]

FIG. 1 is a block diagram of a temperature controller to which an abnormality detection method according to the present invention is applied.

FIG. 2 is an internal circuit diagram of the output unit of FIG.

FIG. 3 is a CP showing an operation of detecting an abnormality of an output unit.
It is a flowchart of U.

FIG. 4 is a diagram showing a display panel of the temperature controller.

FIG. 5 is a block diagram of a conventional system of a temperature controller.

FIG. 6 is a diagram showing an internal circuit of an output unit of the conventional example in FIG.

[Explanation of symbols]

 11A CPU (control means) 16A output unit A control output B output signal C comparator output (comparison signal) CP comparator (comparison means)

Claims (2)

[Claims] 1. A method for detecting an abnormality in a control output device, which outputs an output signal to control a controlled device, wherein a detection voltage generated according to the output signal is compared with a reference voltage to generate a comparison signal. Comparing means and control means for emitting a control output for transmitting the output signal, wherein the control means emits a control output for stopping the output of the output signal when the comparison signal has a predetermined value. Control output device abnormality detection method. 2. The abnormality detection method for a control output device according to claim 1, wherein the control output device is a temperature controller that adjusts the temperature of the controlled device.