JPH11110049A - Water level controller - Google Patents

Abstract

PROBLEM TO BE SOLVED: To prevent the erroneous detection of a water level with a simple circuit constitution by adding a half-wave rectifier circuit to the input side of a water level detector to supply a current to a current detection circuit only when the AC power supply connection side of the water level detection circuit is set at a negative voltage level and accordingly actuating only the circuit that detected the water. SOLUTION: If a terminal 31 of an AC power supply 3 is set at a negative voltage level when the water 10 is set at a level 12, a current successively flows to an AC power supply terminal 32, a water level detection electrode 21, the water 10, a water level detection electrode 22, a diode 41 and then a capacitor 43 and also flows to a resistance 44 and then to an AC power supply terminal 31 respectively. Thus, an FET 47 is turned on via a resistance 46. If the terminal 31 of the power supply 3 is set at a positive voltage level, the current successively flows to the terminal 31, a resistance 45, a diode 42, the electrode 22, the water 10, the electrode 21 and then the terminal 32. Thus, the FET 47 is not turned on. As a result, a water detection circuit 4 operates only when the terminal 31 is set at a negative voltage level. Meanwhile, a water level detection circuit 5 does not operate.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a water level control device provided with a plurality of water level detecting electrodes for detecting the water level of a water tank in stages.

[0002]

2. Description of the Related Art When a water level control device having two or more water level detection points is used, in order to drive the detection circuits as many as the number of the detection points, it is necessary to prevent malfunction.
A completely separate power supply must be used for each detection circuit. This will be described below with reference to the conventional water level detection circuit shown in FIG. In this description, for simplicity, the case where the number of water level detection points is two is exemplified. Further, the target object to be detected is water, but the principle is not limited to water, and the same principle can be applied to a conductive substance. Also, as a current detection circuit,
Although a circuit in which a photocoupler is driven by an FET is taken as an example, the circuit is not limited to this as long as it can detect a current.
In this circuit, it is assumed that the power supplies 49 and 59 for the water level detection circuit are completely separated.

[0003] First, a case where water 10 is contained in water tank 1 by water level 12 will be described. When the terminal 31 of the AC power supply 3 has a positive voltage, the detected current is the AC power supply terminal 31 → the diode bridge 61 → the diode bridge positive terminal 611 → the capacitor 43 and the resistor 44 → the diode bridge negative terminal 612.
→ water level detection electrode 22 → water 10 → water level detection electrode 21 →
The current flows in the order of the AC power supply terminals 32. When the terminal 31 of the AC power supply 3 has a negative voltage, the order in which the current flows to the diode bridge 61 is reverse to the order of the AC power supply terminal 32 → water level detection electrode 21 → water 10 → water level detection electrode 22 → diode bridge 61. The rest is the same.

That is, when the water 10 is at the water level 12, a current flows between the water level detecting electrodes 21 to 22, and a potential difference generated when the current passes through the capacitor 43 and the resistor 44 is applied to the gate of the FET 47 via the resistor 46. Give voltage, FET
Is turned ON, and the L of the photocoupler 48 is
A current flows to the ED, the photocoupler 48 turns on, and the water level detection circuit 6 operates. At this time, the water level detection circuit 7 does not operate because there is no water between the water level detection electrodes 21 to 23 and no current flows, so that the water level 12 can be detected. When the water 10 reaches the water level 13, a current also flows between the water level detection electrodes 21 to 23, and both the water level detection circuits 6 and 7 operate, so that the water level 13 can be detected. When the water 10 reaches the water level 11, no current flows between the water level detection electrodes 21 to 22 and 21 to 23, so that the water level detection circuits 6 and 7 do not operate and the water level 11 can be detected. As described above, if the power supply of the water level detection circuit is completely independent, the water level detection circuit operates without any problem. However, preparing a completely independent power supply requires a complicated circuit configuration.

Next, in order to simplify the circuit configuration, a case where the power supply 49 and the power supply 59 are integrated without being completely separated will be described with reference to FIG. In this circuit, the power supply is 49
And only one. When the water 10 in the aquarium 1 is only at the water level 12, the water level detection circuit 8 operates on the same principle as described above. However, especially the terminal 3 of the AC power supply 3
Only when 1 is a positive voltage, the current is
→ Diode bridge 71 of water level detection circuit 9 → Diode bridge positive terminal 711 → Capacitor 53 and resistor 54
→ Negative terminal 612 of diode bridge of water level detection circuit 8
→ Diode bridge 61 → Water level detection electrode 22 → Water 1
It flows in a detour path of 0 → water level detection electrode 21 → AC power supply terminal 32. This turns on FET57
Then, a current flows from the power supply 49 to the LED of the photocoupler 58, the photocoupler 58 is turned on, the water level detection circuit 9 is also activated, and the water 10 is recognized as having the water level 13 and is erroneously detected. .

[0006]

As described above, as described above,
In the case where there are two or more water level detection points, if the power supplies of the water level detection circuits are not completely separated, the current flows through the detour path, and the water level detection circuit that should not detect water will erroneously detect. For this reason, a completely separate power supply must be made for each detection circuit, which complicates the circuit. SUMMARY OF THE INVENTION The present invention has been made in view of the above points, and has as its object to provide a water level control device which solves these drawbacks, has no erroneous detection, and has a simple circuit configuration. .

[0007]

Means for achieving the object are as follows: 1) In claim 1, the water tank is provided with a plurality of water level detecting electrodes for detecting the water level of the water tank in stages. In a water level control device including a water level detection circuit having a power supply for each water level detection electrode other than the common water level detection electrode located at the lowest position of the water tank, one of the AC power supplies is at the lowest position of the water tank. Connect to a common water level detection electrode located.
The other side of the AC power supply is connected to a common negative side of each water level detection circuit controlled by each water level detection electrode other than the lowest water level detection electrode. The positive side of each of the water level detection circuits is connected to the cathode end of two diodes connected in series in the same direction, and the anode end of the two diodes connected in series in the same direction is connected to the negative end of the water level detection circuit. Side, and a water level detection electrode other than the lowest water level detection electrode is connected to a cathode-anode connection point of a diode connected in series to form a half-wave rectifier circuit, and the respective water level detection circuits are connected. Power supply is common.

[0008] In the second aspect, in the current path changed by the polarity of the AC power supply, the impedance of both paths is equalized to equalize the current value in both directions, thereby preventing a chemical change of the electrode. belongs to. That is, this problem is caused by the fact that the input side of the water level detection circuit is constituted by a full-wave rectifier circuit, so that when the power supply for the water level detection circuit is shared, the AC power connection side of the water level detection circuit input becomes a positive voltage. This is a problem that occurs because of a circuit configuration in which both the water level detection circuits operate.
This can be solved by using a half-wave rectifier circuit on the input side of the water level detection circuit.

The function is as follows. A half-wave rectifier circuit is provided on the input side of the water level detection circuit, in which a current flows through the current detection circuit only when the AC power supply connection side of the water level detection circuit has a negative voltage.
If current is not allowed to flow to the current detection circuit when the AC power supply connection side is a positive voltage, the water level detection circuit will operate only the circuit that detected water, and the water level detection circuit can operate without malfunction. Becomes However, half-wave rectification causes a current to flow in only one direction and adversely affects the water level detection electrode. Therefore, it is necessary to devise a circuit so that current flows in the water level detection electrode in both directions.

Hereinafter, an embodiment of the present invention will be described in detail with reference to the drawings.

FIG. 1 is a circuit diagram showing an embodiment of the present invention. In FIG. 1, the same reference numerals as in FIG. 2 denote portions having the same configuration and function. In FIG. 1, a description will be given of a case where the water 10 has a water level of up to a water level 12 in the water tank 1 which has become a problem as described above. When the terminal 31 of the AC power supply 3 has a negative voltage, the current is supplied to the AC power supply terminal 32 → water level detection electrode 21 → water 10 → water level detection electrode 22 → diode 41 → capacitor 43 and resistor 4
4 → AC power supply terminal 31 flows in this order, and F
ET47 is turned on, and the power of the photocoupler 48 is
A current flows through the ED to turn on the photocoupler 48, and the water level detection circuit 4 operates.

When the terminal 31 of the AC power supply 3 has a positive voltage,
The current is the AC power supply terminal 31 → resistor 45 → diode 42 →
The water flows from the water level detection electrode 22 → water 10 → water level detection electrode 21 → AC power supply terminal 32, and the FET 47 is not turned on. Therefore, when the water 10 is at the water level 12, the terminal 31 of the AC power supply 3
Only when the voltage is negative, the FET 47 is turned on and the water level detection circuit 4 operates. At this time, the water level detection circuit 5
Does not flow at all, the water level detection circuit 5 does not operate, and thus the water level 12 can be detected. The above is the description of the first embodiment.

Regardless of the polarity of the AC power supply 3 described above, the resistance 4
If a value of 5 is set, the same current in both directions flows through the water level detection electrode, so that a chemical change of the electrode can be prevented. The above is the description of the second embodiment.

[0013]

As described above, according to the present invention, even when there are two or more water level detection points, only one power supply for the water level detection circuit is required, and the circuit configuration can be simplified. It is highly useful.

[Brief description of the drawings]

FIG. 1 is a circuit diagram showing one embodiment of the present invention.

FIG. 2 is a road diagram showing an example of the related art.

FIG. 3 is a circuit diagram showing two conventional examples.

[Explanation of symbols]

 Reference Signs List 1 water tank 10 water 11 water level 12 water level 13 water level 21 water level detection electrode 22 water level detection electrode 23 water level detection electrode 3 AC power supply 31 AC power supply terminal 32 AC power supply terminal 4 Water level detection circuit 41 Diode 42 Diode 43 Capacitor 44 Resistor 45 Resistor 46 Resistor 47 FET 48 Photocoupler 49 Power supply for water level detection circuit 5 Water level detection circuit 51 Diode 52 Diode 53 Capacitor 54 Resistor 55 Resistor 56 Resistor 57 FET 58 Photocoupler 59 Power supply for water level detection circuit 6 Water level detection circuit 61 Diode Bridge 61 Diode Bridge Positive Terminal 61 Diode Bridge Negative Terminal 7 Water Level Detection Circuit 71 Diode Bridge 71 Diode Bridge Positive Terminal 71 Diode Bridge Negative Terminal 8 Water Level Detection Circuit 9 Water Level Out circuit

Claims (2)

[Claims] A plurality of water level detection electrodes for detecting the water level of a water tank in stages are provided in a water tank, and each of the water level detection electrodes other than a common water level detection electrode located at the lowest position of the water tank is provided. In a water level control device provided with a water level detection circuit having a power supply, one of the AC power supplies is connected to a common water level detection electrode located at the lowest position of the water tank, and the other of the AC power supplies is connected to the lowest level. The water level detection circuits controlled by the respective water level detection electrodes other than the water level detection electrodes are connected to a common negative side of the respective water level detection circuits, and two positive sides of the respective water level detection circuits are connected in series in the same direction. An anode end of two diodes connected in series in the same direction, connected to a cathode end of the diode, is connected to a negative side of the water level detection circuit, and a water level detection electrode other than the lowest water level detection electrode is connected. ,
A water level control device, wherein a half-wave rectifier circuit is formed by connecting each of the series-connected diodes to a cathode / anode connection point, and a power source of each of the water level detection circuits is common. 2. The water level control device according to claim 1, wherein in a current path changed by the polarity of the AC power supply, the impedance of both paths is made equal to make the current values in both directions equal, thereby preventing a chemical change of the electrode.