EP2175713B1

EP2175713B1 - Driver circuitry for an electronic control unit for irrigation systems, adapted to control ac solenoid electrovalves and dc bistable solenoid electrovalves

Info

Publication number: EP2175713B1
Application number: EP08774771A
Authority: EP
Inventors: Andrea Brundisini; Franco Milan
Original assignee: Claber SpA
Current assignee: Claber SpA
Priority date: 2007-07-10
Filing date: 2008-07-04
Publication date: 2010-12-22
Anticipated expiration: 2028-07-04
Also published as: ATE492155T1; ITMI20071371A1; DK2175713T3; EP2175713A1; ES2357919T3; DE602008004161D1; PT2175713E; WO2009007317A1; PL2175713T3

Abstract

An electronic control unit for irrigation systems, adapted to control AC solenoid electrovalves and DC bistable solenoid electrovalves, includes a driver circuitry for the solenoid which consists of a first circuit (CT1) for the power supply of an AC solenoid (L) and a second circuit (CT2) for the reversible polarity power supply of a DC bistable solenoid (L). An AC voltage is applied to an input terminal (1) of the first circuit (CT1), whereas a DC voltage is applied to an input terminal (2) of the second circuit (CT2). A common terminal of the solenoid (L) is connected to the output terminal of one or the other circuit depending on whether the solenoid itself is of the AC or DC type. The other terminal of the solenoid is grounded by means of a control device (T), specifically a triac (T), in turn controlled by a microprocessor (M).

Description

The present invention relates to a driver circuitry for an electronic control unit for irrigation systems, which is adapted to control AC solenoid electrovalves and DC bistable solenoid electrovalves.
Irrigation systems for broad areas such as gardens, parks, golf courses etc., as known, include a plurality of electrovalves intended to start and interrupt the supply of water to a plurality of irrigation devices distributed at appropriate positions in the areas to be irrigated.
The control of the electrovalves relies on electronic control units, commonly designated as "control units", which may be one or more for each irrigation system and may be distributed at different positions, even far from one another, each being dedicated to the control of a respective plurality of electrovalves. In case of multiple control units, the remote programming thereof is usually provided by means of a single PC which may be connected in different manners.
The electrovalves used in irrigation systems may include AC solenoids or DC solenoids, in this case of the bistable type.
Each type has its advantages and drawbacks and it is usually the installer who decides which one is to be used depending on the cost, on the electric power available, on the operation safety and so on.
Usually, the control units are selected depending on the type of solenoid employed, even if control units are known which allow to switch from one to the other of two different operating conditions, for AC solenoids and for DC bistable solenoids.
To exploit such a switching possibility, a certain circuit complexity is required, which is hardly combined with the need to use many control units at limited costs and size, which do not require frequent maintenance operations.
It is the object of the present invention to provide, instead, an electronic control unit, which may readily be used for the control both of AC solenoid electrovalves and DC bistable solenoid electrovalves as desired by the installer, while limiting costs, size and the need for maintenance.
According to the present invention such an object is achieved by means of a driver circuitry for an electronic control unit, characterised in that it includes a first circuit for the power supply of an AC solenoid, a second circuit for the reversible polarity power supply of a DC bistable solenoid, an input terminal for said first circuit which may be connected to an AC voltage source, an output terminal for said first circuit to which a common terminal of the solenoid may be connected, an input terminal for said second circuit which may be connected to a DC voltage source as an alternative to said first circuit input terminal, an output terminal for said second circuit to which said common terminal of the solenoid may be connected as an alternative, a control device for the driver current of the solenoid interposed between a second terminal of the solenoid and ground and a microprocessor dedicated to the control of said control device depending on the AC or DC voltage that may be detected at said input terminals.
Thereby, without the need for complicated, expensive and cumbersome switching means between an AC mode and a DC mode, the same control unit is allowed to drive an AC solenoid or a DC bistable solenoid by simply connecting the common terminal of the solenoid to the output terminal of the first or second power supply circuit.
It is then the microprocessor which detects the type of voltage applied and accordingly controls the driving of the control device of the solenoid. As an alternative, a selector may be included providing the microprocessor with information about the operating mode.
The features and advantages of the present invention will become apparent from the following detailed description of an embodiment thereof, shown by way of non-limitative example in the accompanying drawings, in which:

Figure 1 shows a diagrammatic representation of the control circuitry for the control unit according to the present invention;
Figure 2 shows a specific example of control circuitry for the control unit according to the present invention.
Figure 1 diagrammatically shows a control circuitry for a solenoid L, which may be of the AC type or of the DC bistable type.

To allow the driving both of a solenoid of the first type and of a solenoid of the second type, the above said circuitry includes a first circuit CT1 adapted to supply AC current and a second circuit CT2 adapted to supply reversible polarity DC current.
An AC voltage Vac is applied to an input terminal 1 of the circuit CT1, the AC voltage Vac occurring again at an output terminal 3 of the same circuit, whereas a DC voltage +Vdc is applied to an input terminal 2 of the circuit CT2, the DC voltage +Vdc occurring again with the same polarity or with an inverted polarity at an output terminal 4 of the circuit CT2.
The circuitry in Figure 1 also includes a driver device for the solenoid L, which consists of a triac T provided with a control gate G in turn controlled by an appropriately programmed microprocessor.
The solenoid L has a first terminal or common terminal 5 and a second terminal or output terminal 6, the first of which may be connected to the output terminal 3 of the circuit CT1 if the solenoid L is of the AC type and to the output terminal 4 of the circuit CT2 if the solenoid L is of the DC bistable type, whereas the second terminal is connected in any case to the input terminal 7 of the triac T, the output terminal 8 of which is grounded.
Therefore, the control unit always has the possibility of driving the solenoid of the electrovalve to which it is connected, whether the solenoid employed is of the DC bistable type or of the AC type.
The microprocessor M may be allowed to detect the type of power supply (AC or DC current) and accordingly drive the gate of the triac T.
Figure 2 shows a more detailed example of the circuitry according to the present invention, in which the circuit CT1 consists of a simple lead powered by a voltage Vac.
The circuit CT2 instead includes a step-up voltage transformer TM, the secondary of which is provided with a central tap 30 to the ground potential.
The primary of the transformer M is connected to an inlet circuit which includes a Zener diode Z1, a transistor Q1, a resistor R1 and a capacitor C1 and is supplied to the clamp P with a variable duty-cycle, square wave voltage Vp, whereas the secondary provides the simultaneous charge of the capacitors Con and Coff through the diodes D1 and D2 connected to one another by means of a Zener diode Z2.
Two discharge circuits PCon and PCoff are provided, which are controlled by the clamps Pon and Poff, by the microprocessor M. The clamp Pon is connected through a resistor R4 to the base of a transistor Q2 of the NPN type, which has the source connected to ground, as well as to the base of the same transistor by means of a resistor R5, and the collector connected by means of the resistors R3 and R2 to the source of a transistor Q1 of the PNP type which is interposed between the capacitor Con and the terminal Vdc and has the base connected to an intermediate node between the resistors R2 and R3. The clamp Poff is in turn connected through a resistor R8 to the base of a transistor Q4 of the PNP type, which has the collector connected to ground, as well as to the base of the same transistor by means of a resistor R9, and the source connected by means of resistors R7 and R6 to the source of a transistor Q3 of the NPN type which is interposed between the capacitor Coff and the terminal Vdc and has the base connected to an intermediate node between the resistors R6 and R7.
By enabling Pon, the capacitor Con, charged with +Vdc, may discharge on the solenoid L at the same time as the enabling of the gate G of the triac T, thus activating the solenoid itself.
By enabling Poff, the capacitor Coff, charged with -Vdc, may discharge on the solenoid L at the same time as the enabling of the gate G of the triac T, thus deactivating the solenoid itself.
By charging the capacitors Con and Coff at the same time, the circuit with the transformer in figure 2 halves the time otherwise needed for the control of the solenoid with the inverter circuit.

Claims

A driver circuitry for an electronic control unit for irrigation systems, adapted to control AC solenoid electrovalves and DC bistable solenoid electrovalves, characterised in that it includes a first circuit (CT1) for the power supply of an AC solenoid (L), a second circuit (CT2) for the reversible polarity power supply of a DC bistable solenoid (L), an input terminal (1) for said first circuit (CT1) which may be connected to an AC voltage source, an output terminal (3) for said first circuit (CT1) to which a common terminal (5) for the solenoid may be connected, an input terminal (2) for said second circuit (CT2) which may be connected to a DC voltage source as an alternative to said first circuit (CT1) input terminal (1), an output terminal (4) for said second circuit (CT2) to which said common terminal (5) of the solenoid (L) may be connected as an alternative, a control device (T) of the driver current of solenoid (L) interposed between a second terminal (6) of the solenoid (L) and ground and a microprocessor (M) dedicated to the control of said control device (T) depending on the AC or DC voltage that may be detected at said input terminals (1, 2).
A driver circuit according to claim 1, characterised in that said control device (T) is a triac with a gate G which is controlled by said microprocessor (M).
A driver circuitry according to claim 1 or 2, characterised in that said second circuit (CT2) includes a step-up voltage transformer (TM), the secondary of which is provided with a central tap (30) to the ground potential and provides the simultaneous charge of two capacitors (Con, Coff), two discharge circuits (PCon, PCoff) being provided, which are controlled at respective clamps (Pon and Poff) by said microprocessor (M) so that, by enabling one of said clamps, one of said capacitors may be discharged on the solenoid (L) at the same time as the enabling of said control device (T), thus activating the solenoid itself, whereas the enabling of the other clamp at the same time as the enabling of said control device (T) induces the discharge of the other capacitor on said solenoid (L) for the deactivation of the same.