JPS6245561B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a circuit that automatically corrects errors caused by the length of a remote control wire that transmits electrical signals when performing closed-loop control of equipment using a remote control.

When performing remote control control, a single wire is often used to transmit various signals in order to reduce the number of remote control wires that connect the device and the controller and transmit signals. In particular, various feedback currents are often passed through the ground line wires of electrical circuits, and when this and the status detection signal line are shared, the detected value and set value may deviate due to the voltage drop caused by the current flowing through the wire. I had something to put away. The present invention relates to a circuit for correcting errors caused by the length of the wire.

The present invention will be explained below using an example in which the present invention is applied to controlling the outlet temperature of a gas instantaneous water heater.

FIG. 1 shows a conventional control system in which the temperature of a water heater is controlled by a remote control.

A indicates the water heater body, B indicates the remote control cable, and C indicates the remote control box. The water heater A has a water supply port 1 and a hot water supply faucet 2, and a heat exchanger 3 is provided in the middle thereof. The gas passes through the main valve 5 and the control valve 6 from the gas inlet 4 and is burned in the burner 7 to heat the heat exchanger 3. Reference numeral 8 indicates a pilot burner, and reference numeral 9 indicates a flow rate switch that detects water flow and turns on and off the contacts. Further, a hot water temperature detector 10 is provided at the outlet of the heat exchanger 3.

The remote control box C has a built-in control circuit connected to a power source 11 and a power switch 12.

If the power switch 12 is turned on now, the main valve 5
is energized and sends gas to the pilot burner. At the same time, an ignition circuit (not shown) operates to ignite the pilot flame. Here, when the faucet 2 is not open, the flow rate switch 9 is open, so the resistors 13 and 14
The midpoint, that is, the base potential of the transistor 15 becomes the potential of the power supply 11, and the retransistor 15 is cut off. Therefore, the control valve 6 is closed because there is no power supply.

Next, when the faucet 2 is opened, the flow rate switch 9 becomes conductive. Therefore, since the resistor 14 is connected to the ground line of the power source 11, the base potential of the transistor 15 becomes the divided potential of the resistors 13 and 14, and the transistor 15 becomes conductive. This supplies power to the operational amplifier 16 and the detection bridges 17, 18, 19, and 20.

Resistors 19 and 20 are connected to the input terminal of the operational amplifier 16.
divided potential a, resistor 17 and temperature setting volume 1
The divided potentials b of 8 and sensor 10 are compared, and the difference is amplified by the ratio of resistors 21 and 22 and output.
The output of the operational amplifier 16 is divided by resistors 23 and 24 and connected to the base of a transistor 25.

Now, when the water temperature is low, the resistance of the sensor 10 increases (an example in which the sensor 10 uses a negative temperature-sensitive resistance element), so the potential b>a and the operational amplifier 1
Since the output potential of transistor 25 increases by the gain times (ba), the base potential of transistor 25 increases,
Collector current increases.

A control valve 6 is connected to the collector of the transistor 25. The control valve 6 is an electromagnetic gas proportional control valve that varies the amount of gas in proportion to the current flowing through the electromagnetic coil.As the current increases, the amount of gas also increases, the amount of combustion increases, and the temperature of the water increases. .

Here, the cable 26 connecting the line of the power source 11 includes the main valve 5, the control valve 6, and the sensor 1.
A feedback current I of 0 flows. Therefore, the cable 26
, a voltage drop of e=I·R occurs due to I.
(R is the cable resistance) As a result, the temperature sensing bridge section becomes an equivalent circuit as shown in FIG.

In FIG. 2, if there is a voltage drop e, the resistance value of the sensor 10 needs to be smaller than when there is no e, in order for the potential b to be equal to a. In other words, the set temperature becomes higher. This is proportional to the magnitude of the voltage drop e. Further, the voltage drop e changes depending on the resistance R of the cable, that is, the length of the cable. Temperature control volume 18 because the longer the cable, the higher the set temperature.
There was a problem where the desired water temperature could not be obtained even after adjusting the water temperature.

27 is a resistor for compensating the input current of the operational amplifier;
8 indicates the emitter resistance of the transistor 25.

Therefore, FIG. 3 shows an embodiment of the present invention, and FIG. 4 shows its equivalent circuit.

In the equivalent circuit shown in FIG. 4, changes in voltage drop e are detected by operational amplifier 29 and potential a is corrected.

In other words, operational amplifier 29 and resistors 30, 31, 32
constitutes a non-inverting amplifier, and the input potential e
is amplified by the ratio of resistors 30 and 32 and output. The output of the operational amplifier 29 is connected through a resistor 33 to a point φ obtained by dividing the potential a by resistors 34 and 35.
Resistor 30, so that the potential e is generated at c as it is,
Values of 32, 33, and 35 are designed.

As a result of the above, the potential a is also pushed up by the amount that the potential b is pushed up by the potential e, and even if the potential e changes, the resistance value of the sensor 10 where the potential a=b is the same as when the potential e is not present. Become. In other words, even if a voltage drop e occurs due to the cable, the set temperature does not change at all.

The actual circuit diagram is shown in FIG.

Here, the positive side f of the potential e (earth potential on the device side) is obtained from the cable 36.

The current I' flowing through the cable 36 is the resistance 13, 14.
Since the current passes through the cable 2, by making the resistors 13 and 14 sufficiently large, I' becomes very small.
Since it is considered that there is almost no voltage drop across the cable 26, the potential on the main body f side of the cable 26 can be detected by f' on the controller C side. Therefore, even if the cable length changes as explained in FIG. 4, the set temperature remains the same as when the cable length is zero.

Although the above description has been made using remote control of a water heater as an example, the present invention can be widely applied to other devices in which various processes are controlled using a remote control.
In FIG. 3, D is a control circuit that drives and controls the control valve 6, and E is a circuit that automatically corrects the set value according to the length of the remote control wire B.

As explained above, the remote control correction circuit of the present invention has the following effects.

(1) A correction circuit installed in the control circuit built into the remote control box detects the voltage drop due to the length and current of the ground wire that connects one side of the sensor and one of the power supply lines to other loads, and Since the configuration corrects the set value of , the detection conditions of the sensor do not change even if the distance between the main body and the remote control, that is, the length of the remote control wire, changes depending on the installation conditions.

(2) Similarly, a correction circuit works to respond to changes in the load current flowing through the common ground wire, always maintaining a constant detection condition.

(3) Furthermore, since one wire of the sensor and the common ground wire can be shared, the number of remote control wires can be reduced and construction work can be simplified.

[Brief explanation of the drawing]

Figure 1 is a conventional water heater control system circuit diagram.
FIG. 2 is an equivalent circuit diagram illustrating the effect of voltage drop due to the conventional remote control wire in FIG. This figure is an equivalent circuit diagram explaining the operation of the present invention in FIG. 3. 6... Control valve (actuator), 10... Water temperature detector (sensor), 26... Common ground wire, 3
6...Wire for detecting the ground potential on the equipment side, A...
Water heater body, B...Remote control wire, C...Remote control box, D...Control circuit, E...Automatic correction circuit.

Claims (1)

[Claims] 1. A sensor that detects the state of a device and converts it into an electrical quantity, an actuator that changes the state of the device using an electric signal provided in the device, and a control that drives the actuator by comparing the signal of the sensor with a set value. The control circuit is built in a remote control box located away from the device, the control circuit and the actuator and sensor are electrically coupled by a plurality of remote control wires, and the remote control wire has a , a ground wire that shares one lead wire of the sensor and one of the power supply lines to the other load, and a wire that detects the ground potential on the equipment side of the ground wire, and A remote control correction circuit configured to include a circuit that automatically corrects the set value according to a potential difference.