JPH0750204A - Digital control system variable resistor - Google Patents

Abstract

PURPOSE:To satisfy the continuity of the output resistance value of the title variable resistor and the speed of response of the variable resistor by a method wherein the variable resistor is constituted into such a structure that a binary code sent as a digital control signal is connected to each resistance value of resistors, which are kept series-connected to a group of weighted resistors, or a bias is performed conforming to a binary signal and the output resistance value is obtained. CONSTITUTION:Relays 2 are actuated on the basis of a binary code signal 1 of a binary number. For example, the relays of a bit No.1 and a bit No.3 are excited at a value of 10 in a decimal number, a switch on the side of a contact (a) to correspond to the relay of the bit No.1 is turned off, a switch on the side of a contact (b) to correspond to the relay of the bit No.3 is turned on and a combined resistance value of (255R-2R-8R=245R) excluded the resistance values of 2Rs and 8Rs is obtained between output terminals 4 and 4a. Similarly, a combined resistance value of 2R+8R=10R is obtained between the terminal 4 and an output terminal 4b and a constant combined resistance value of 255Rs is obtained between the terminals 4a and 4b. A control reference resistance value R is decided according to the whole resistance value, which is required for the title variable resistor, or a circuit which is used.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention is applied to a machine operation simulation in which a resistance value is fed back to a control panel as an element representing a position such as a pump blade angle and a valve opening, and
In terms of programming, the present invention relates to a digitally controlled variable resistor used together with digital control.

[0002]

2. Description of the Related Art Some variable resistors used for automatic control utilize angular displacement of a potentiometer caused by rotation of a linear motor via a servo amplifier as shown in FIG.

For those which do not require precise control, there is a method of obtaining a required resistance value by switching a switch as shown in FIG. In order to apply either method to digital control, both continuity and response speed cannot be satisfied, and in addition, adjustment work on the finished product is necessary to obtain the required accuracy. . Even if the required accuracy is obtained by the adjustment work, there remains a problem in terms of resolution.

Taking the variable resistor using the potentiometer of FIG. 6 which is considered to be a relatively high-grade product as an example, (1) it takes several seconds until the resistance value is saturated, which is caused by a moving part. The problem is that it is difficult to maintain accuracy due to deterioration over time. In order to make up for this problem, it is necessary to wait for a certain period of time before taking in data, to provide a dedicated protection circuit in preparation for contact failure, and to perform data averaging processing.

[0005]

However, the above-mentioned prior art cannot satisfy both the continuity of the output resistance value and the response speed. On the other hand, the control panel delivered to operate equipment such as pumping stations sends out control values based on feedback of the state position of the equipment, but when evaluating the control performance of this control panel, the conventional technology However, it has been impossible to give a controlled time delay or to give a feedback signal of a starting process of a plurality of devices that are simultaneously proceeding according to a planned program.

According to the present invention, by connecting or bypassing the resistor network weighted corresponding to the binary code by digital control, both the continuity of the output resistance value and the response speed are satisfied, and the plurality of feedback signals described above are satisfied. The problem is solved by programming and giving. In addition, the software program for digital control converts the control reference resistance value R to a power supply voltage to output a current signal and a voltage signal, and converts the shunt ratio (power supply) and the voltage division ratio (voltage). Directly output in decimal without doing.

[0007]

In order to solve the above object, binary codes sent as digital control signals are connected in series like weighted resistor groups R, 2R ,. Connect or bypass the resistance value according to the binary signal to obtain the output resistance value.

A relay contact may be used for connection or bypass of each resistance value, or a semiconductor circuit may be turned on and off by a signal insulated by a photocoupler.

In order to solve the problems of continuity and responsiveness of resistance value control, the binary code sent is controlled by a digital control software program, and continuity and resolution are practically acceptable. In order to make it, the number of bits of binary is decided to the required number.

When a three-terminal type variable resistor is made as in the case of taking out a voltage signal output, the above resistor groups are connected in series like back-to-back connection, and then the respective resistance values are connected.
Bypassing is performed by making one contact at the a contact and the other at the b contact, and pull out the three terminals from both ends and the midpoint (Fig. 1,
This example is described as an 8-bit type).

The resistor determines the required wattage from the circuit voltage used, and if the resistance value does not have a standard value, the standard value is combined as necessary.

[0012]

FIG. 1 shows an example of an 8-bit digitally controlled variable resistor. In the figure, the binary code signal 1 in binary number operates the relay 2. For example, a decimal value of 10 means that the relays of bit # 1 and bit # 3 are excited, so the corresponding a-contact side switch is closed and the b-contact side switch is open. As a result, between the output terminals 4-4a, the combined resistance value (255R-2R-8R = 245R) excluding the resistances of 2R and 8R is obtained.
Is obtained. Similarly, between 4-4b, 2R + 8R = 10
Since a resistance of R is obtained and a constant resistance of 255R is obtained between 4a and 4b, if an equivalent circuit is shown, it is expressed as shown in the right side figure.

As the binary number increases, the resistance value of the terminal 4-4a decreases to 0 ohm, and the resistance value between 4-4b becomes
It will increase up to 255R ohms. The value of the control reference resistance R is determined according to the required total resistance value or the circuit used. For example, when applied to a circuit for current output as shown in FIG. It is possible to simplify the software program by relating it as an integer multiple of.

Reason: Current I = (power supply voltage) / R × (digital number) ... Therefore, the value of R is an integer n of the power supply voltage.
If doubled, the current I is calculated as 1 / (digital number) × n.

Reference numeral 5 is a capacitor for smoothing fluctuations that occur when the switches are switched.

[0016]

EXAMPLE FIG. 2 shows a circuit for directly taking out a resistance output.
The software program for digital control is shown on the right. A control reference resistance value R = 10 ohms is set to obtain a 0-2550 ohm digitally controlled variable resistor. In this example, since the signal input is 8 bits, the resolution is 1/255, that is, 0.4%.

FIG. 3 shows a circuit for extracting the current output. R
By associating 12 ohms with the power supply voltage of 12 volts, the same output current value is output when the decimal current value is commanded by the software program on the right side. The current limiter in the figure is a circuit overcurrent protection.

FIG. 4 shows a circuit for extracting the voltage output. For the purpose of voltage output, a three-terminal variable resistor is used, and R = 80 ohms is set because the power supply voltage is 100 V, so the total resistance is limited by the power consumption. It is considered that about 80 ohms) × 255 = 20400 ohms are necessary. In the case of the example of this figure, the value of R need not be related to the power supply voltage or the output voltage.

(Vs = Vt × digital number × R / 255R ...
Because R is offset. )

[0020]

The digitally controlled variable resistor of the present invention is
In addition to the resistance value output, both current and voltage can be output as controlled signals in combination with a constant power supply voltage, so it has become possible to precisely verify the characteristics of control products for pumping stations.

Further, since the product of the present invention is highly functionalized by digital control using a network of a collection of inexpensive parts such as resistors and relay switches which are distributed as standard products, the number of control channels is increased. However, the price of the increase is
It is extremely cheap to make.

Further, a minute current peculiar to digital control
Since the resistance circuit of the present invention is insulated from the voltage control, it is possible to directly use the digital control in the power circuit, for example, by controlling the rotation speed by using the secondary resistor control of the wound-type induction motor. Become.

[Brief description of drawings]

FIG. 1 is an explanatory diagram of a digitally controlled variable resistor according to the present invention.

FIG. 2 is a circuit diagram of an embodiment of the present invention product.

FIG. 3 is a circuit diagram of an embodiment of the present invention product.

FIG. 4 is a circuit diagram of an embodiment of the present invention product.

FIG. 5 is an explanatory diagram of an example of a conventional technique.

FIG. 6 is an explanatory diagram of an example of a conventional technique.

[Explanation of symbols]

1 ... Binary code signal, 2 ... Relay coil, 3a ... Switch group a contact, 3b ... Switch group b contact, 4a ... Output terminal (decreasing side), 4c ... Output terminal (moving terminal), 4b ...
Output terminal (increasing side), 5 ... Smoothing capacitor.

Claims (1)

[Claims] 1. When a resistor group weighted corresponding to a binary code is adjusted in its overall resistance value by digital control of a corresponding switch group and the resistor group is weighted, the value of a control reference resistor R is A digitally controlled variable resistor characterized in that, when manufacturing a device for obtaining an output voltage or current in accordance with or related to a power supply voltage, a conversion program for dividing voltage and dividing current is simplified by software.