JPS63140931A - Variable resistance switch driving circuit - Google Patents

Abstract

PURPOSE:To reduce the consumption of a battery by turning off a switch circuit when a resistance variation factor does not operate. CONSTITUTION:A tactile sensor 1 and a 2nd resistance body 2' are connected in series and a 1st resistance body connected in parallel to the tactile sensor 1 constitutes a detecting circuit by interposing a switch 5. A voltage comparator formed by connecting resistance bodies 6 and 7 in series is provided in parallel to the series circuit of the tactile sensor 1 and 2nd resistance body 2 and a comparator 8 which compares their divided voltages with each other is connected to constitute a bridge circuit. The switch 5 is driven with a signal outputted by the comparator 8. The comparator 8 operates only when a pressing force is applied to the tactile sensor 1 and the resistance 4 is connected in parallel to the tactile sensor 1.

Description

[Detailed Description of the Invention] [Industrial Application Field] The present invention relates to a circuit for driving a switch in a circuit in which a pressure-sensitive conductive rubber is inserted in parallel with an element whose resistance decreases exponentially with respect to a pressing force. It is related to.

[Prior art]

Pressure-sensitive conductive rubber has long been known to act as an insulator when no force is applied, and its resistance rapidly decreases when pressure is applied, and this pressure-sensitive conductive rubber has been used as a tactile sensor. Various technological developments are underway. For example, by attaching this tactile sensor to a robot hand, the robot itself can recognize the gripping force when holding an object to be handled, and
BACKGROUND OF THE INVENTION Development is underway to equip robots with functions similar to those that humans have when determining soft objects, etc., and to develop devices that can recognize the shape of objects through the sense of touch.

By the way, the resistance value R of this pressure-sensitive conductive rubber and the force F that presses the rubber have a relationship of approximately log R+a -F-'°9, so the relationship between force and resistance value does not change linearly. There is a characteristic, which is illustrated in Figure 3. Note that a in the above formula is a constant.

Now, with reference to the circuit shown in FIG. 4, the characteristics of a tactile sensor using pressure-sensitive conductive rubber whose resistance changes will be explained.

The tactile sensor L shown in the figure has a configuration in which a pressure-sensitive conductive rubber R is sandwiched between a pair of electrodes E. For example, two horizontal electrodes are arranged so as to engage with each other using printed wiring, and a sensor is placed on top of the two horizontal electrodes. A tactile sensor 1, such as one on which a piezoconductive rubber is mounted and a conductive film is preferably arranged on the opposite side.
The electrode structure can be constructed in various ways.

Now, a resistor 2 is connected in series with this tactile sensor 1, and the voltage generated at the voltage dividing point A is applied to an amplifier 3.
The relationship between the pressing force F applied to the pressure-sensitive conductive rubber R and the resistance change of the pressure-sensitive conductive rubber R is shown in FIG.

That is, when the force F is zero, the resistance value of the pressure-sensitive conductive rubber R has the resistance value of an insulator, so no current flows and the voltage at point A is V.
is zero. Next, as the force F increases, the resistance decreases rapidly, so the voltage (2) becomes an exponential curve toward the power supply voltage VD. Therefore, when using this pressure-sensitive conductive rubber as a sensor to detect force or control a robot, etc., the sensitivity changes greatly depending on the value of force F, making it difficult to perform stable control. A fixed resistor is connected in parallel with the conductive rubber to make the voltage change more linear.

This circuit will be explained with reference to FIG. In the figure, a first resistor 4 that makes the detected voltage change of the tactile sensor 1 more linear is connected in parallel with the tactile sensor 1, and a second resistor 2' for voltage division is connected in series with this parallel circuit. The voltage generated at the voltage dividing point A is applied to the amplifier 3.

In this case, as shown in FIG.
Since a current flows through the voltage divider point A, a voltage 1 is generated from the beginning at the voltage dividing point A, and when the force F becomes sufficiently large, the resistance value of the pressure-sensitive conductive rubber R approaches zero, and the first resistor 4 is short-circuited. The diagonal divided voltage is the power supply voltage ■ as in Figure 5.

Since the voltage curve approaches , the voltage curve becomes a gentler curve than that shown in FIG.

However, if such a circuit is installed in a battery-powered robot, current will flow through the circuit even when no force is acting on the tactile sensor, so if the power supply is limited, such as with a battery, is where the problem lies. Therefore, if the power of the tactile sensor is turned off when the force F is not acting on the tactile sensor, the problem arises that it cannot be detected when the force F is acting on the tactile sensor, which is not preferable.

[Purpose of the invention]

The present invention has been made to solve the above problems, and is a method for linearizing resistance changes of elements such as pressure-sensitive conductive rubber and thermistors whose resistance decreases cumulatively. It is an object of the present invention to provide a switch drive circuit that uses a resistor in a circuit that uses the resistor, detects the effect of a factor that changes the resistance of the resistor, and causes current to flow through the parallel resistor.

[Structure of the invention]

In order to achieve the above object, the variable resistance switch drive circuit of the present invention includes a second resistor in a circuit in which a first resistor and an element whose resistance decreases cumulatively in response to resistance fluctuation factors are connected in parallel. In a circuit that is connected in series and detects a voltage applied to the second resistor to detect a change in resistance of the element, a switch is interposed in the parallel connected resistor circuit, and the voltage applied to the second resistor is The present invention is characterized in that a switching circuit is provided that opens the switch when a predetermined value is reached.

Examples of elements to which the present invention applies include pressure-sensitive conductive rubber, thermistors, etc., and the resistance fluctuation factors are the force of pressing the pressure-sensitive conductive rubber for the former, and the temperature for the latter.

The switch interposed in the first resistor circuit of the present invention may include a contact switch such as a relay, a transistor,
The present invention is not limited thereto, although the present invention is not limited thereto.

The switching circuit of the present invention includes a bridge circuit whose sides include the element according to the present invention and the second resistor, and the bridge circuit detects a voltage change applied to the second resistor, thereby switching the switch. This can be realized by a driving switching circuit or the like.

〔Example〕

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS The present invention will be specifically described below with reference to an embodiment using pressure-sensitive conductive rubber with reference to the accompanying drawings.

FIG. 1-a shows the switch circuit of this embodiment, in which the tactile sensor 1 and the second resistor 2' are connected in series as described above, and the first resistor 2' is connected in parallel with the tactile sensor 1. A switch 5 is interposed in the resistor 4 to constitute a detection circuit similar to that shown in FIG. The switching circuit for driving this switch 5 includes a voltage comparison circuit in which resistors 6 and 7 are connected in series in parallel to the series circuit made up of the tactile sensor 1 and the second resistor 2. A comparator 8 for comparing piezoelectric voltages is connected to form a Brifuji circuit,
The switch 5 is driven by the signal output from the comparator 8.

By setting the resistance values of the resistors 6 and 7 to a predetermined value, the pressing force F becomes a constant value, and the comparator continues until a predetermined voltage (the same value as the voltage generated at point A) is generated at point B. 8 can be disabled.

Therefore, when the voltage ■ at point B (and at the same time point A) reaches the predetermined voltage ■3, it becomes higher than the voltage generated at point 0, and a high signal is given from the comparator 8 to the switch 5, and the first resistor 4 The circuit shown in FIG. 6 is closed to form a circuit similar to that shown in FIG. Therefore, the voltage generated at point A has a curve as shown in FIG. 2-a. This curve and the curve in FIG. 7 are similar curves (assuming the circuit constants are the same) except until the switch 5 is closed, and provide desirable pressing force detection characteristics as a tactile sensor when operating a robot, etc. be able to.

Since the voltage generated at voltage dividing point C of the comparison circuit is simply compared with the voltage at point B, the resistance values of the resistors 6 and 7 can be set to high values. Therefore, while the force F applied to the tactile sensor 1 is small, the current flowing through the detection circuit is extremely weak, so the power source is not consumed while the pressing force F is zero or very small. Therefore, it can be advantageously used in battery-powered robots, portable tactile sensors, and the like.

Next, a modified embodiment of the circuit diagram of FIG. 1-a is shown in FIG. 1-S. That is, in FIG. 1-b, the polarity of voltage application is reversed from that in FIG. 1-a.

When the circuit is configured in this way, the voltage generated at point A when no pressing force is applied to the tactile sensor 1 is the pressure-sensitive conductive rubber R.
■Power supply voltage due to high resistance.

The voltage is equal to

Next, when a pressing force F is applied, the resistance of the pressure-sensitive conductive rubber R decreases accordingly, so that the partial pressure value V3 generated at point A and point B decreases. Therefore, when the voltage drops to a predetermined level, similar to the circuit shown in FIG. -b voltage changes in a curve of 2.

In this manner, the variable resistance switch drive circuit of the present invention is capable of gradually increasing the pressing force or decreasing it by 7fi.

〔Effect of the invention〕

As explained above, in the variable resistance switch drive circuit of the present invention, a second resistor is connected in series to a circuit in which an element whose resistance decreases cumulatively in response to resistance fluctuation factors and a first resistor are connected in parallel. In the circuit for detecting a change in resistance of the element by detecting the voltage applied to the second resistor, a switch is interposed in the parallel-connected resistor circuit, and the voltage applied to the second resistor is set to a predetermined value. By providing a switching circuit that opens the switch when the resistance change factor reaches , no substantial current flows through the switch circuit when the resistance variation factor does not act.
Furthermore, the element can be kept in an operating state at all times.

Therefore, it can be advantageously applied to a circuit where the power supply capacity of a power source is limited, using elements such as pressure-sensitive conductive rubber and thermistors whose resistance decreases cumulatively in response to the above-mentioned resistance fluctuation factors.

[Brief explanation of the drawing]

FIG. 1-a is a circuit diagram of one embodiment, FIG. 1-a is a circuit diagram of another embodiment, and FIG. Fig. 2-b is a graph showing the relationship between the pressure force acting on the tactile sensor of Fig. 1 and the detected voltage, and Fig. 3 is a graph showing the relationship between the pressure sensitive conductive rubber and the resistance. A graph showing the relationship with the pressing force, Figure 4 is a circuit diagram showing the principle for detecting the force applied to the tactile sensor using pressure-sensitive conductive rubber as a voltage, and Figure 5 shows the relationship between the tactile sensor shown in Figure 4. A graph showing the relationship between the applied pressing force and the detected voltage, FIG. 6 is a circuit diagram using conventional means to make the voltage-pressing force relationship shown in FIG. 5 more linear, and FIG. 7 is a circuit diagram shown in FIG. FIG. 3 is a graph diagram showing the relationship between the pressing force acting on the tactile sensor and the detected voltage. DESCRIPTION OF SYMBOLS 1... Tactile sensor, 2... Second resistor, 4... First resistor, 5... Switch, 6.7... Resistor, 8
...Comparator, R...Pressure-sensitive conductive rubber, E...
electrode.

Claims (1)

[Claims] A second resistor is connected in series to a circuit in which a first resistor and an element whose resistance decreases cumulatively in response to a resistance variation factor are connected in parallel, and the voltage applied to the second resistor is detected. In the circuit for detecting a change in resistance of an element, a switch is interposed in the parallel-connected resistor circuit, and a switching circuit is provided that opens the switch when the voltage applied to the second resistor reaches a predetermined value. Features a variable resistance switch drive circuit.