JPH0625767U - Potentiometer resistance converter - Google Patents

Abstract

(57) [Summary] [PROBLEMS] To provide a potentiometer resistance value converter capable of detecting a potentiometer disconnection by allowing the detected value to be swung in a predetermined direction of an upper limit or a lower limit when the potentiometer is disconnected. [Structure] The digital arithmetic circuit 12 takes in the resistance value of the potentiometer POT via a multiplexer a for each sampling period, and determines whether or not a disconnection has occurred between terminals UP 'and between terminals CP'. , Also, terminal L every 2 seconds
It is determined whether or not a wire break has occurred between -P '. When a disconnection occurs, the input normalized data is set to a value that is more than a preset upper limit value or less than a preset lower limit value and can be swung in a predetermined direction. The output circuit 13 converts this value into a voltage or a current and outputs it.

Description

[Detailed description of the device]

[0001]

[Industrial applications]

 The present invention relates to a potentiometer resistance value converter that converts a resistance value corresponding to a position of a potentiometer slider into a voltage output.

[0002]

[Prior art]

 FIG. 7 shows a resistance value converter of a conventional potentiometer. This converter has terminals U, L, and C for connecting a potentiometer, and both ends of the resistance of the potentiometer are connected to the terminals U and L to apply a reference voltage. A potentiometer slider is connected to the terminal C, and a piezoelectric voltage corresponding to the position (terminal) P of the slider is detected via the filter circuit 1 and the insulation circuit 2, and the output circuit 3 By converting into detection current and detection voltage, respectively, measurement can be performed via each detection meter (not shown).

[0003]

[Problems to be solved by the device]

 However, in the above-mentioned conventional potentiometer converter, when the terminals U-P, L-P, and C-P are disconnected or opened, the input voltage of the filter circuit 1 becomes higher than the upper limit (100%) or The detection meter is shaken off below the lower limit (0%), but since the direction of this shakeout depends on the disconnection point, it is possible to determine whether this shakeout is due to a disconnection or a range over. There is a problem that you cannot do it.

In view of the above-mentioned conventional problems, the present invention provides a potentiometer resistance value capable of detecting a potentiometer disconnection such that when the potentiometer is disconnected, the detection value can be swung in a predetermined direction of an upper limit or a lower limit. The purpose is to provide a converter.

[0005]

Means for Solving the Problems The present invention relates to a potentiometer resistance value converter for converting a potentiometer resistance value into a voltage output, and a first detection circuit for detecting the potentiometer resistance value by a voltage and a potentiometer disconnection. A second detection circuit for detecting the voltage by a voltage, and a first detection circuit that selectively takes in the voltage detected by the first or second detection circuit and detects the disconnection by the second detection circuit. It has a disconnection detection means that outputs the value detected by the circuit above the upper limit value or below the lower limit value.

[0006]

[Action]

 According to the present invention, when the potentiometer is disconnected, the disconnection detecting means sets the detection value of the potentiometer to be equal to or higher than the upper limit value or equal to or lower than the lower limit value. Therefore, the disconnection of the potentiometer can be detected.

[0007]

【Example】

 Embodiments of the present invention will be described below with reference to the drawings. The converter shown in FIG. 1 has terminals U, L, and C for connecting a potentiometer POT. The terminals U and L are connected to both ends of the resistance of the potentiometer, and the terminal C is connected to the potentiometer. A pendulum (terminal P'in the figure) is connected.

Then, a constant current from the constant current source CCS1 is applied to the terminal U and the disconnection detection circuit 10 as shown in detail in FIG. 4, and the connection point Y of the resistors R3 and R4 of the disconnection detection circuit 10 forms the multiplexer a. It is connected to the DC amplification circuit 11 via. Further, the terminal C is connected to the DC amplification circuit 11 via the multiplexer a and is also connected to a negative voltage via the constant current source C CS2. The terminal L is connected to the voltage AG.

The voltage between the terminals C and L or the voltage between the connection point Y and the terminal L is selectively taken in and amplified by the DC amplifier circuit 11 via the multiplexer a, and then the digital arithmetic circuit 12 causes the potentiometer to operate. The value converted by the digital arithmetic circuit 12 is converted to a detected value when the value is normal, and converted to a value equal to or higher than a preset upper limit (100%) or lower limit (0%) when the wire is disconnected. It is converted into a detection voltage or a detection current (output “1”, “2”) by the circuit 13 and used according to the application.

Next, the disconnection state of the potentiometer POT will be described with reference to FIGS. 2 and 3. When disconnection occurs when the disconnection detection circuit 10 shown in FIG. 1 is not connected, the input voltage VIN of the differential amplifier U1 of the DC amplification circuit 11 becomes as shown in FIG. That is, the voltage VIN is 0 because the current from the constant current source CCS1 (0.8 mA) flows into the constant current source CCS2 (0.4 mA) on the terminal C side when a disconnection occurs between the terminals CP. If the output voltage is out of the measurement range due to overshooting below%, and if a wire breakage occurs between terminals L and P, the constant current from constant current source CCS1 (0.8 mA) is applied to the + input terminal side of differential amplifier U1. As it flows in, it will shake out to more than 100% and fall outside the measurement range.

Therefore, when a disconnection occurs between the terminals C-P 'and between the terminals L-P', the digital arithmetic circuit 12 causes the direction in which the voltage between the terminals C-L is cut off during normal sampling. Thus, it is possible to identify the disconnection point.

On the other hand, when a wire breakage occurs between the terminals U and P ', the voltage VIN varies depending on the position of the slider. That is, when the slider is located in the middle of the resistance, the constant current source CC S2 (0.4 mA) swings it to less than 0% and it is out of the measurement range, but when the slider is located at the terminal L, Since the resistance value on the terminal L side is 0Ω, the voltage VIN becomes 0V. Therefore, the disconnection between the terminals U-P 'cannot be detected.

Next, the operation of the disconnection detection circuit 10 when a disconnection occurs between the terminals U and P ′ will be described with reference to FIG. When the total resistance value of the potentiometer POT is, for example, 5 KΩ, the input / output voltage Va of the differential amplifier 11a and the voltage Vb at the connection point Y under normal conditions are Va = I × (R1 + R2 + RPOT) + VD. Here, if I = 0.8 mA, R1 = R2 = 2 KΩ, RPOT = 5 KΩ, and VD = 1.4 V, then Va = 8.6 V. Further, since the differential amplifier 11a is saturated at the time of disconnection, Va = 11V (saturation voltage), for example. When the input range of the A / D converter 12a of the digital arithmetic circuit 12 is -2.5 V to +2.5 V, the above 8.6 V to 11 V exceeds this input range, so R3 = 9.09 KΩ, R4 = 3.32KΩ is selected and the voltage Va is divided, Vb = 2.3V or less (normal) = 2.9V (broken). Therefore, it is possible to detect the disconnection between the terminals U and P'by switching the multiplexer a and fetching the divided voltage Vb at a constant cycle.

Next, the operation of the digital arithmetic circuit 12 will be described with reference to FIGS. 5 and 6.

First, the hardware (H / W) is initialized (step S 1), self-diagnosis of this initialization is performed (step S 2), and whether a sampling period for taking in the voltage between the terminals C and L has elapsed It is determined whether or not (step S3).

Then, the input calculation processing routine as detailed in steps S41 to S43 is executed for each sampling period (step S4), and the output calculation processing routine as detailed in steps S51 to S53 is executed ( In step S5), online self-diagnosis is executed (step S6).

In the input operation processing routine shown in step S4, a disconnection detection routine as detailed in steps S411 to S419 of FIG. 6 is executed (step S41). In this disconnection detection routine, first, the voltage between the terminals C and L is fetched through the multiplexer a, and it is determined whether the difference between the detected value and the previous detected value is 5% or more (step S411). When it is 5% or more, the multiplexer a is switched to capture the voltage Vb at the wire breakage detection point Y (step S412), and when the voltage Vb is 2.5 V or more, wire breakage occurs between the terminals UP and P '. (Step S413), the process proceeds to step S421.

If the difference is not 5% or more in step S411, and if the voltage Vb is not 2.5 V or more in step S412, it is determined whether or not the detected value has fallen below 0% (− side). Then, if it is shaken out (step S414), it is determined that a disconnection has occurred between the terminals CP '(step S415), and the process proceeds to step S421. In addition, it is determined whether or not the detected value is 100% (+ side) or more, and when the detected value is out of range (step S416), it is determined that a disconnection has occurred between the terminals LP '(step S417). ), And proceeds to step S421.

When the detected voltage has not been swung out in either direction, when the timer has elapsed for 2 seconds (step S418), after resetting the timer, the multiplexer a is switched to change the voltage Vb at the disconnection detection point Y. If this voltage Vb is detected twice and the burnout voltage is equal to or lower than -2.5 V (step S419), it is judged that a disconnection has occurred between the terminals UP and P '(step S420). Proceed to S421.

In step S421, the burnout flag is turned on, and in steps S42 and S43, the input data of the voltage between the terminals C and L is normalized, and the process proceeds to the output calculation processing routine shown in step 5. If the timer has not elapsed for 2 seconds in step S418 or if the voltage Vb is not below the burnout voltage twice in succession in step S419, the burnout flag is not turned on directly and steps S42 and S43 are performed. To the output calculation processing routine.

In the output calculation processing routine, it is determined whether or not the burnout flag is on, and if it is on, the input normalized data is swung in the predetermined direction above the upper limit value or below the preset lower limit value. The value is set (step S52) and output to the output circuit 13 shown in FIG. 1 (step S52). If the burnout flag is not on, the input normalized data is output as it is to the output circuit 13 (step S52).

Therefore, according to the above-described embodiment, even when the disconnection occurs at any place between the terminals UP and P ′, between the terminals CP ′ and between the terminals LP ′, the detected value becomes the upper limit. It is possible to detect the disconnection of the potentiometer by swinging in a predetermined direction above the value or below the lower limit.

[0023]

[Effect of device]

 As described above, according to the present invention, when the potentiometer is broken, the detection value of the potentiometer is set to the upper limit value or more or the lower limit value or less, so that the potentiometer disconnection can be detected.

[Brief description of drawings]

FIG. 1 is a circuit diagram showing an embodiment of a resistance value converter of a potentiometer according to the present invention.

FIG. 2 is a circuit diagram for explaining when the potentiometer is disconnected in the resistance value converter of the potentiometer shown in FIG.

FIG. 3 is an explanatory view showing a state at the time of each disconnection in FIG.

FIG. 4 is a circuit diagram for explaining the operation of the disconnection detection circuit of FIGS. 1 and 3.

5 is a flowchart for explaining the operation of the digital arithmetic circuit in FIG.

FIG. 6 is a flowchart for explaining a disconnection detection routine in FIG.

FIG. 7 is a circuit diagram showing a resistance value converter of a conventional potentiometer.

[Explanation of symbols]

POT ... Potentiometer, a ... Multiplexer, 10
... disconnection detection circuit, 11 ... DC operation circuit, 12 ... digital operation circuit, 13 ... output circuit.

Claims (1)

[Scope of utility model registration request] 1. A potentiometer resistance value converter for converting a resistance value according to the position of a slider of a potentiometer into a voltage output, wherein a first detection circuit for detecting the resistance value of the potentiometer by voltage and a disconnection of the potentiometer. A second detection circuit for detecting the voltage by a voltage, and selectively detecting the voltage detected by the first or second detection circuit and detecting the disconnection by the second detection circuit, the first detection circuit A potentiometer resistor converter having a disconnection detecting means for setting a value detected by a circuit to be equal to or higher than an upper limit value or lower than a lower limit value and outputting the value.