JPH0547874U - Variable resistor output detector - Google Patents

Abstract

(57) [Summary] [Purpose] To quickly detect an abnormal condition such as a short circuit or disconnection of a variable resistor. [Configuration] Microcomputer 1 with A / D conversion circuit
2 is fed from the constant voltage circuit 13. Variable resistor 20
Is fed from the constant voltage circuit 13 via the current limiting resistor 15. The microcomputer 12 determines that the voltage is normal when the voltage of the power supply terminal 20a of the variable resistor 20 is within a predetermined range, and corrects the variable output voltage based on the voltage to perform an accurate detection operation. When the voltage of the power supply terminal 20a of the variable resistor 20 is out of the predetermined range, a warning signal is output to the buzzer 14 because a short circuit accident or a wire break accident has occurred. Therefore, stable detection operation can be performed.

Description

[Detailed description of the device]

[0001]

[Industrial applications]

 The present invention relates to an output detection device for a variable resistor, which detects a variable output voltage of a variable resistor used for a sensor or the like to detect the resistance value thereof.

[0002]

[Prior Art]

 Conventionally, when a variable resistor is used as a displacement amount sensor, for example, the circuit configuration is as shown in FIG. That is, in FIG. 3, the microcomputer 1 has an A / D conversion circuit inside and is supplied with power from the constant voltage circuit 2. An overcurrent detection circuit 3 is connected to the constant voltage circuit 2, and when the output current of the constant voltage circuit 2 exceeds a predetermined value, the overcurrent detection circuit 3 detects the overcurrent and stops the output. It has become.

The variable resistor 4 converts the detection amount of the sensor into a resistance value, and its power supply terminal 4 a is connected to the output terminal of the constant voltage circuit 2 and to the input terminal V of the microcomputer 1. The ground terminal 4b is grounded and is connected to the input terminal E of the microcomputer 1. A variable output terminal 4c of the variable resistor 4 is connected to an input terminal S of the microcomputer 1 via an integrating circuit composed of a resistor 5 and a capacitor 6.

According to such a configuration, the microcomputer 1 inputs the output voltage of the constant voltage circuit 2 and the terminal voltage of the variable output terminal 4c of the variable resistor 4, and outputs the digital signal by the A / D conversion circuit. Then, the resistance value of the variable resistor 4 is detected by calculating the ratio of these voltage values.

However, in such a configuration, for example, when the power supply terminal 4a of the variable resistor 4 is short-circuited with the ground terminal 4b due to incorrect wiring, the overcurrent detection circuit 3 detects the short-circuit current at that time. Then, if the output of the constant voltage circuit 2 is stopped, the microcomputer 1 to which power is supplied from the constant voltage circuit 2 is also stopped and the detection operation becomes impossible.

Therefore, in order to solve such a problem, as shown in FIG. 4, instead of providing the overcurrent detection circuit 3, a current limit is provided between the power supply terminal 4 a of the variable resistor 4 and the constant voltage circuit 2. A structure having a resistor 7 interposed is considered.

With such a configuration, even when the short-circuit accident as described above occurs, the current limiting resistor 7 limits the energizing current, so that an overcurrent may flow on the variable resistor 4 side. Disappear. As a result, the microcomputer 1 maintains the power supply state and the operating state is ensured.

[0008]

[Problems to be solved by the device]

 However, in the conventional device as described above, when the short circuit accident occurs in the variable resistor 4, the operating power supply of the microcomputer 1 is secured, but the voltage applied to the variable resistor becomes abnormal, Since the variable output voltage of the variable resistor 4 cannot be normally converted and processed, it may be erroneously detected.

The present invention has been made in view of the above circumstances, and an object thereof is to prevent malfunction even when a power supply terminal of a variable resistor is short-circuited, and also to provide an abnormality such as a short-circuit state or a disconnection of the variable resistor. An object is to provide a variable resistor output detection device capable of detecting a state.

[0010]

[Means for Solving the Problems]

 The output detecting device of a variable resistor of the present invention detects a variable resistor to which a power supply voltage is applied via a current limiting resistor, a voltage applied to this variable resistor, and a variable output voltage from the variable resistor. When the voltage value applied to the variable resistor is within a predetermined range, the detection circuit and the notifying means are provided, and the detection circuit and the notification circuit are provided based on the voltage value and the variable output voltage value. It is characterized in that the resistance value of the container is detected, and when it is not within the predetermined range, the notification means is caused to perform the notification operation.

[0011]

[Action]

 According to the output detection device of the variable resistor of the present invention, the variable resistor is supplied with power through the current limiting resistor, and the voltage and variable output voltage applied to the variable resistor are detected by the detection circuit. .. At this time, the detection circuit detects the resistance value of the variable resistor based on the voltage value and the variable output voltage value when the voltage applied to the variable resistor is within the predetermined range. As a result, for example, even if the voltage applied to the variable resistor fluctuates due to variations in the overall resistance value, accurate detection operation can be performed.

When the terminal on the power feeding side of the variable resistor is short-circuited with the terminal on the ground side, the current flowing is limited by the current limiting resistor, so that the power supply is not short-circuited. The power supply for the detection circuit is secured. At this time, the detection circuit detects that the voltage at the power supply terminal of the variable resistor is lower than the lower limit of the predetermined range, and notifies by the notifying means that a short circuit has occurred.

On the other hand, when there is a disconnection between the power supply terminal of the variable resistor and the current limiting resistor, no current flows in the variable resistor. The terminal voltage of is the same as the power supply voltage value. The detection circuit detects that the voltage at the power supply terminal of the variable resistor exceeds the upper limit of the predetermined range, and notifies the notification means that a disconnection accident has occurred.

[0014]

【Example】

 An embodiment of the present invention will be described below with reference to FIGS. 1 and 2.

In FIG. 1 showing the electrical configuration, the controller 11 is provided with a microcomputer 12 which is a detection circuit having an A / D conversion circuit inside, and operates according to a detection program described later. There is. The constant voltage circuit 13 is connected to the power supply input terminal VD and the power supply voltage input terminal VS of the microcomputer 12, supplies power to the microcomputer 12 and applies a predetermined voltage to the power supply voltage input terminal VS. ..

The output terminal P of the microcomputer 12 is connected to the buzzer 14 serving as a notification means via the output terminal 11p of the controller 11. The power supply voltage input terminal VS of the microcomputer 12 is connected to the terminal 11a via the current limiting resistor 15.

The reference voltage input terminal SS is grounded via the capacitor 16 and connected to the terminal 11 a via the resistor 17. The detection voltage input terminal SK is grounded via the capacitor 18 and connected to the terminal 11b via the resistor 19. The ground terminal E is grounded and connected to the terminal 11c.

Incidentally, the condenser 16 and the resistor 17, the condenser 18 and the resistor 19 respectively configure the integrator circuits A and B, and the input voltage applied to the microcomputer 12 from the terminals 11a and 11b changes rapidly. I try not to.

The variable resistor 20 as a sensor is a device such as a potentiometer that detects a displacement amount corresponding to a detection amount by converting it into a variation amount of a resistance value, and its power supply terminal 20a and variable output terminal 20b. And the ground terminal 20c are connected to the terminals 11a, 11b and 11c of the controller 11, respectively.

Next, the operation of this embodiment will be described with reference to the detection program shown in the flowchart of FIG.

Since a current flows from the constant voltage circuit 13 through the current limiting resistor 15 to the variable resistor 20, a voltage drop occurs, and a voltage corresponding to each of the terminals 11a to 11c of the controller 11 is input. It In the microcomputer 12, the output voltage Vref of the constant voltage circuit 13 is input as a reference voltage for A / D conversion from the power supply voltage input terminal VS, and between the reference voltage input terminal SS and the terminals 20a and 20c of the variable resistor 20. The voltage V1 is input, and the output voltage V2 of the variable output terminal 20b of the variable resistor 20 is input to the detection voltage input terminal SK.

The microcomputer 12 converts the analog voltage signals input to the input terminals SS and SK into digital signals by the A / D conversion circuit using the output voltage Vref as a reference, and then takes in the data as input signals. Run the detection program based on.

That is, when the microcomputer 12 starts the detection program, first, it is determined whether the reference voltage V1 input from the reference voltage input terminal SS is smaller than the lower limit comparison voltage T1 of the preset predetermined range. Is determined (step S1). In this case, if the terminals 20a to 20c of the variable resistor 20 are normally connected to the controller 11, the reference voltage V1 is within the predetermined range, so that the reference voltage V1 is larger than the comparison voltage T1. The microcomputer 12 determines “NO” and proceeds to step S2.

Next, in step S2, the microcomputer 12 determines whether or not the above-mentioned reference voltage V1 is higher than the upper limit comparison voltage T2 of the predetermined range. Similarly to the above, when the variable resistor 20 is normally connected to the controller 11, the reference voltage V1 is within the predetermined range, so that the reference voltage V1 is smaller than the comparison voltage T2. Then, the process proceeds to step S3.

In step S3, the microcomputer 12 corrects the magnitude of the detection voltage V2 input from the detection input terminal SK based on the magnitude of the reference voltage V1. This is to prevent an error from occurring when the reference voltage V1, that is, the voltage applied to the variable resistor 20 is fluctuated, if it is used as it is based on the detected voltage V2. As a result, even if the total resistance value of the variable resistor 20 varies, it is always obtained as the ratio of the detected voltage V2 to the reference voltage V1 as the applied voltage, so that the amount of displacement can be accurately detected.

Next, the case where the power supply terminal 20a of the variable resistor 20 is in contact with the ground side due to a short circuit accident will be described. In this state, since the terminal 11a of the controller 11 is grounded, no voltage is applied to the variable resistor 20 and the entire voltage is applied to the current limiting resistor 15.

At this time, since the energizing current is limited to a constant value by the current limiting resistor 15, the output of the constant voltage circuit 13 is not short-circuited, and the power supply voltage input terminal VS of the microcomputer 12 is The power supply voltage Vref of the constant voltage circuit 13 is input as in the normal state. However, the reference voltage V1 of approximately zero volts is input to the reference voltage input terminal SS, and the detection voltage V2 of approximately zero volts is also input to the detection voltage input terminal SK.

As a result, the microcomputer 12 determines “YES” because the reference voltage V1 is smaller than the lower limit comparison voltage T1 in step S1, and proceeds to step S4. Then, in this step S4, the microcomputer 12 outputs a short-circuit notification signal to the buzzer 14 to determine that a short-circuit accident has occurred, sounds the notification pattern corresponding to the short-circuit accident, and stops the detection operation.

On the other hand, the case where the power supply terminal 20 a of the variable resistor 20 and the terminal 11 a of the controller 11 are disconnected will be described. That is, in this state, since the variable resistor 20 is not supplied with power, no current flows through the current limiting resistor 15, so that the reference voltage V1 becomes substantially the same as the power supply voltage Vref.

As a result, the microcomputer 12 determines “NO” in step S1, and then determines “YES” in step S2 because the reference voltage V1 is higher than the upper limit comparison voltage T2 in step S2. Move to. In step S5, the microcomputer 12 outputs a disconnection notification signal to the buzzer 14 to determine that a disconnection accident has occurred, causes the buzzer 14 to ring in a notification pattern corresponding to the disconnection accident, and stops the detection operation.

According to the present embodiment as described above, when the connection state between the variable resistor 20 and the controller 11 becomes abnormal and a short circuit accident, a wire disconnection accident, or the like occurs, the microcomputer 12 causes the reference voltage V1 to change. When the value is out of the predetermined range set by the lower and upper comparison voltages T1 and T2, this is detected and the buzzer 14 is caused to ring, so that any abnormality such as a short circuit accident or a wire break accident is detected. Can be detected quickly.

Further, according to the present embodiment, when the connection state between the variable resistor 20 and the controller 11 is normal, the fluctuation of the detection voltage V2 caused by the variation of the resistance value of the variable resistor 20 Since the correction is made based on the reference voltage V1, accurate detection operation can always be performed.

In the above-described embodiment, the buzzer 14 is used as the notification means, but the present invention is not limited to this, and the notification may be made by a light such as a lamp.

[0034]

[Effect of the device]

 As described above, according to the output detecting device of the variable resistor of the present invention, the power supply voltage is applied to the variable resistor through the current limiting resistor, and the detection circuit detects the applied voltage of the variable resistor to determine the predetermined value. When it is within the range, the variable output voltage is corrected based on the applied voltage, and when it is not, the alarm means is made to perform an alarm operation as an abnormality, so that the variable resistor is short-circuited or disconnected. When this occurs, it has an excellent effect that it can be detected promptly, and even when it is normal, the variation in the resistance value can be corrected to always perform an accurate detection operation.

[Brief description of drawings]

FIG. 1 is an electrical configuration diagram showing an embodiment of the present invention.

FIG. 2 is a flowchart of a detection program.

FIG. 3 is a view corresponding to FIG. 1 showing a conventional example.

FIG. 4 is a view corresponding to FIG. 1 showing a different conventional example.

[Explanation of symbols]

11 is a controller, 12 is a microcomputer (detection circuit), 13 is a constant voltage circuit, 14 is a buzzer (informing means), 15 is a current limiting resistor, 16 and 18 are capacitors,
Reference numerals 17 and 19 are resistors, and 20 is a variable resistor.

Claims (1)

[Scope of utility model registration request] 1. A variable resistor to which a power supply voltage is applied via a current limiting resistor, a detection circuit for detecting a voltage applied to the variable resistor and a variable output voltage from the variable resistor, and an informing means. When the voltage value given to the variable resistor is within a predetermined range, the detection circuit detects the resistance value of the variable resistor based on the voltage value and the variable output voltage value, and within the predetermined range. An output detecting device for a variable resistor, characterized in that when not present, the notifying means is caused to perform a notifying operation.