ES2579489B1 - Remote control system of the electric position of a potentiometer - Google Patents

Abstract

Remote control system of the electrical position of a potentiometer that, inserted at the connections of its ends to the original control system, offers control inputs that allow a secondary or remote control system to eventually modify the resistance balance on both sides of the Cursor of the potentiometer, and with it its electrical position, keeping the resistance seen by the original control system invariably when its control inputs are activated, thanks to a base circuit that makes the insertion of a resistor in series with one of the ends of the potentiometer, and connects a parallel resistor that compensates for equivalent resistance variation, and with calculation algorithms that allow you to easily obtain and adjust the appropriate values of the components for a wide range of applications, potentiometer values and control margins .

Description

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D E S C R I P C I O N

REMOTE CONTROL SYSTEM OF THE ELECTRICAL POSITION OF A

POTENTIOMETER

TECHNICAL SECTOR

The present invention falls within the field of control systems, remote control, and remote control technology.

BACKGROUND OF THE INVENTION

The potentiometer is a device widely used as a position sensor in command and control devices. As an example we will mention the volume control of a radio receiver, the temperature setpoint selector of an oven, or its use in the automotive sector, as is the case with some marine engine control levers, which incorporate a potentiometer that allows to govern the motor regime and / or the drive of the gear inverter.

In any of the examples cited, and in many others, it is sometimes desirable to be able to operate the existing control potentiometer from an alternative command post, in a location different from that of the original command, or to have a remote control system that allows certain mobility Some control systems incorporate, as part of the system, or as an option, the possibility of having a second command post or a remote control. In some cases the simultaneous use of the remote control and the main control is allowed; as in some audio equipment, which incorporates a motorized volume potentiometer, which can be adjusted from a wireless remote control, but which can also be operated manually. In other cases, it is allowed to choose which command post is the one that you want to use at any time, a very frequent case in the case of the double command posts of some motor boats.

However, the existing control system does not always include, nor as an option, the ease of having a second command post, or remote control, or it is desired to incorporate additional features or features not provided by the remote or secondary control post. The original system. Then the need arises to solve the

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interconnection of an external remote control system with the main control system. In some cases, the remote control system does not need to offer the full functionality of the main command system, but it is sufficient to offer a discrete set of operation points. This is the case of some remote control systems for motor boats, used in low-speed maneuvers, in which it is only necessary to engage the gear inverter in forward or backward, modifying little or nothing the engine rotation regime in idle

To address this design problem, different approaches are known. A first approach would be to design a custom solution, integrated into the original control system. But this forces it to design specific solutions and to have design details for each specific control system, which is not always possible. This approach also includes the case in which the existing control system includes some communications bus, through which the control elements transmit the different parameters of government to the controlled elements, and it is intended to offer an alternative command post solution emulating or supplanting the messages of some element of command, such as the levers of government in the case of marine engines.

Another approach to the problem is to interact directly with the control potentiometer of the existing control system, considering that this potentiometer is usually an accessible and separate or detachable part of the control system, which facilitates access to the potentiometer connections or cables or buses that bind it to the control electronics.

In US Patent 7,104,212B2 a remote control system for motor boats is mentioned which is connected in parallel with the control levers of existing engines. By eventually connecting a resistance between the cursor of a potentiometer and one of its ends, it is possible to achieve a discrete variation of the cursor voltage, thereby modifying the working point of the controlled system; This can be used to facilitate remote control of the system's operating point. This concept is applicable to remote control systems for boat docking, such as the one described in the cited patent, in which it is sufficient for the remote control to activate the engine control lever in a few specific positions; back-neutral-avant, in that particular case.

But the parallel connection of a resistive load between the potentiometer cursor and one of its ends has important disadvantages. First, a path is established

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of current circulation through the potentiometer cursor, with the risk of exceeding its operating limits and damaging it, considering that the potentiometers used as position sensors usually support very small cursor currents, since they are designed to function as voltage dividers, with cursor currents much smaller than the current between the ends of the potentiometer.

Another important drawback of the parallel connection mentioned above is that the equivalent resistance seen by the control electronics decreases, which can trigger the systems for detecting faults or errors in the potentiometer and wiring that the control electronics sometimes incorporates. The alteration of the potentiometer's working point could, on the other hand, cause the control system to not work according to plan.

On the other hand, the cited parallel connection system is not suitable so that the remote control system and the main control can be used simultaneously, since, if the position of the potentiometer cursor is changed while the parallel resistor remains connected, the equivalent resistance of the set, modifying the working point of the potentiometer; in addition, the current through the cursor could also be increased, if the movement is towards the opposite end to that to which the parallel resistance has been connected, the maximum current allowed through the cursor may be exceeded.

An additional design problem is to achieve galvanic isolation between the remote control system and the potentiometer and its control electronics, so that the system is easily coupled to existing installations. It is also very important to ensure that the remote control interface system is robust and reliable, and that, when not operational, does not alter the operation of the original system.

The system we propose satisfactorily solves all the indicated problems. We do not know the existence of a system such as the one that is the subject of this patent, which solves in a simple way all the problems raised, allowing to have a general purpose system to remotely modify the electric position of the cursor of a potentiometer .

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DESCRIPTION OF THE INVENTION

The present invention relates to a system that allows the electric position of the cursor of a potentiometer to be modified, solving all the drawbacks indicated above. With the term electric position of a potentiometer we refer to the ratio between the resistance value between the potentiometer cursor and the end of the potentiometer that is established as a reference, and the value of the potentiometer resistance between its two ends.

The system we propose, which is represented conceptually in Figure 1, includes a circuit (102) intended to be inserted between the ends of the potentiometer (101) and its connection points in the original control system (103). This circuit includes control inputs (105) that allow the electric position of the potentiometer to be modified, when activated from the remote or secondary control system (105). The potentiometer cursor connection (107) to the original control system (104) is not altered. Neither the potentiometer (107), nor the control system to which it was connected (104), nor the remote or secondary control system itself form part of this invention.

The basic circuit, essential in this invention, is the one represented in figure 2. The objective of this circuit is to achieve, by means of a control signal activated at will from a secondary control system or remote control, the insertion of a series resistor with one of the ends of the potentiometer, altering the balance of resistances on both sides of the cursor, and with it the electrical position thereof; and at the same time connect a parallel resistor that makes it possible to compensate for the variation in resistance between ends derived from the insertion of the series resistor.

Terminals (201) and (209) represent the circuit inputs, which will be connected respectively to each of the ends of the control potentiometer. Terminals (204) and (207) are the outputs of the circuit, and will be connected to the original control system. For this it would have been necessary to disconnect the ends of the potentiometer. The potentiometer cursor connection is not affected.

The circuit includes a controlled switch closed at rest (203) and a controlled switch open at rest (205). If both switches are at rest, the series resistor, which we will call Ra (202) is bridged, and the parallel resistance, which we will call Rb (206) disconnected, so that the terminals (201) and (204), and the

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terminals (207) and (209) are directly connected. But, if we activate both switches, applying the appropriate control signal at its control inputs (208), the resistance Ra (202) will be inserted, or interleaved, in series between terminals (201) and (204), and the resistance Rb (206) will be connected in parallel between terminals (204) and (207).

If we take as a reference terminal, for the purpose of defining the electrical position of the potentiometer, the terminal (209), electrically equivalent to (207), and we call:

• Rc = value of the resistance of the potentiometer between its ends

• Rc ’= Resistance value between terminals (204) and (207), which will be the resistance seen by the original control system.

• P = Electric position of the potentiometer, referred to the reference terminal, obtained with the terminal (201) disconnected from the circuit, equivalent to the quotient between the current resistance between its cursor and the reference terminal, divided by the resistance of the potentiometer, Rc.

• P ’= Electrical position equivalent to the circuit output, obtained as the resistance between the potentiometer cursor and the reference terminal, divided by the resistance Rc’, with terminals (204) and (205) disconnected,

We will obtain that, if the switches are both at rest, Rc '= Rc, and P' = P, making the circuit a direct connection of the potentiometer to its original control system, and keeping this the same control functionality that it had when it was connected directly to the control system.

When both switches are activated, the insertion of Ra and connection of Rb occurs. From the analysis of the circuit in these conditions it follows that:

(P ’/ P) = Rc / (Ra + Rc) and

Ra = Rc (P-P ’) / P’

Therefore, we can achieve a relative variation of the electric position of the potentiometer cursor by activating both switches, relative variation that depends only on the value of the resistance Ra and the value of the potentiometer itself. This relative variation will be

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less than or equal to unity; that is, the new electric position will be less than or equal to the electric position with both switches at rest, and is constant and independent of P, once the resistance Ra is chosen.

If we now establish the condition that the equivalent resistance Rc ’must be equal to that of the potentiometer, we will obtain that:

Rb = Rc (1 + Rc / Ra)

That is, for any real Ra there is a value of Rb that will cause, when activating both switches, the equivalent resistance of the set seen from the original control system is the same as that of the potentiometer between its ends.

As we have seen, a P 'is thus achieved that will be less than or equal to P. If we want the electrical position to increase, instead of decreasing, there is nothing more than to exchange between each other the connections of the ends of the potentiometer at the entrance of the circuit (201 and 209), and also exchange the output connections to the control system (204 and 207), so that the resistance Ra can be inserted at the other end of the potentiometer.

The circuit described is also reversible in the sense that we can exchange the input connections with the output connections: (201) for (204), and (209) for (207), resulting in a circuit like the one in Figure 3. In that case, when the switches are both at rest, the result of the previous case is maintained: P '= P and Rc' = Rc. However, when both switches are activated, when performing a new circuit analysis, we get:

P ’/ P = RbRc / (Ra (Rb + Rc) + RbRc)

If we apply the restriction that the equivalent resistance Rc ’be equal to that of the potentiometer, (both switches being activated), we will obtain the following equations:

P ’/ P = (1-Ra / Rc)

Ra = Rc (1-P ’/ P)

Rb = Rc (Rc / Ra - 1)

We can, as in the previous case, obtain pairs of values for Ra and Rb, for an Rc

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given, that they fulfill that the resistance of the set with the activated switches is equal to Rc, also achieving the desired relative decrease of the value of the electric position of the potentiometer. However, this configuration does not have the advantage that the relative variation of the electrical position is independent of the resistance value Rb.

Controlled switches must offer galvanic isolation between their control inputs and switch contacts, low contact resistance and high switching speed; They are not subject to this patent, there are commercial models suitable for this use.

The resistors Ra and Rb can be fixed value resistors, calculated for a specific application, or variable resistors, or potentiometers, or combinations of them, which will allow to adjust in situ the desired electric position variation when the switches are activated. From this we can obtain a discrete variation of the electric position of the control potentiometer cursor. By adding in series new series resistance-parallel resistance assemblies with their controlled switches, we can add new discrete control points, and also combine them to produce variations in different directions, according to which end of the potentiometer the corresponding Ra series resistance insertion is made . An example with two basic circuits connected to allow variations of the electrical position in both directions is shown in Figure 4.

The series and parallel resistors could also be, or include, resistors or potentiometers of controlled value, of which there are many types and models in the market. Thus we could achieve a remote control system with quasi-continuous variation of the relative electrical position of the cursor, if we add a calculation module, which, based on the mathematical relationships described, obtain the values of the appropriate control signals to adjust the resistances series and parallel Ra and Rb, to then activate the controlled switches and thus obtain the desired setpoint value variation, maintaining the equivalent resistance of the set equal to that of the original potentiometer.

There are many advantages of the system described. In the first place, it is a minimally invasive system, since the connections of the control potentiometer to its controlled system are only modified when the control inputs are activated, maintaining the rest of the time a connection practically equal to the original, of which only it differs in that the signals from the ends of the potentiometer must pass through the closed contacts at rest of the controlled switches. That is, in case the system

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If the remote control or the interface described is inactive or even switched off, the set is practically equivalent to the system in its original configuration, given the passive nature of the switching elements and the resistors. This results in the robustness and reliability of the system.

The proposed system is also inherently independent of the type, polarity and levels of the electrical signals that the controlled system applies to the control potentiometer (provided that the design limits of the components used are not exceeded), thanks to the galvanic isolation between signals of control and controlled elements, such as resistors and switches, and the passive nature of these components.

The risk problems of exceeding the maximum current through the potentiometer cursor inherent to the parallel connection of a resistive element between the potentiometer cursor and one of its ends are also resolved, since the solution described does not include any connection that can increase said stream. In addition, the original potentiometer cursor connection is not intercepted, nor is any direct connection made on it.

The aforementioned problem of controlled systems incorporating monitoring and fault detection techniques of the potentiometer is also resolved: by keeping the equivalent resistance of the assembly constant, it is avoided that the controlled system can interpret the activation of the remote control as a fault; however, all the fault detection capabilities of the original system are maintained, both with the remote control activated and at rest.

On the other hand, the described solution allows both the remote control and the control potentiometer to be used simultaneously, combining its effects, without modifying the equivalent resistance of the set, nor increasing the current through the cursor of the potentiometer.

This system is a universal solution, of general purpose, because it can be easily adapted to the specific value of the control potentiometer, and be independent of the type and value of the voltages used by the original potentiometer, and provide galvanic isolation between the control lines and the potentiometer and controlled system.

The simplest realization includes a series resistance set, parallel resistance, and controlled switches open at rest and closed at rest, and a control line

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common to both. With this we will achieve a discrete increase or decrease in the setpoint value, depending on which end of the potentiometer the series resistance has been inserted.

Another realization, applicable to the remote control of motors of motor vessels that use motor control levers with potentiometers, includes two series-parallel sets, operating each of the sets on one of the ends of the potentiometer, so that we could increase or decrease the setpoint value by operating the corresponding control line from the remote control system. It is also possible to increase the number of discrete setpoint values by adding more control sets as indicated, connecting them in series, or in a collapsed configuration similar to that shown in Figure 4, for only two control points, and with different acting senses.

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BRIEF DESCRIPTION OF THE DRAWINGS

To complement the description that is being made and in order to help a better understanding of the characteristics of the invention, an set of drawings is attached as an integral part of said description in which, with an illustrative and non-limiting nature, it has been represented the next:

Figure 1.- Shows a block diagram of the interconnection of the invention with the other elements of the control system.

101: Potentiometer end connections

102: Device object of the invention, inserted between the ends of the potentiometer and the original control system.

103: Terminals of the original control system for potentiometer connection.

104: Original control system.

105: Device control lines 106: Remote or secondary control unit

Figure 2.- Shows a basic circuit model.

201: Upper input terminal.

202: Series insert resistor, Ra 203: Control switch closed at rest 204: Upper output terminal 205: Control switch open at rest 206: Resistance connected in parallel, Rb 207: Lower output terminal.

208: Switch control signal input.

209: Lower input terminal.

Figure 3.- Shows an alternative basic circuit model.

301: Upper input terminal.

302: Series insertable resistor, Ra 303: Control switch closed at rest 304: Upper output terminal 305: Control switch open at rest 306: Resistance connected in parallel, Rb 307: Lower output terminal.

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308: Switch control signal input.

309: Lower input terminal.

Figure 4.- Shows an example, not limitative, of preferred realization.

401: Upper input terminal.

402: Relay contacts (418), closed at rest.

403: Adjustable resistance potentiometer or Ras.

404: Relay contacts (418), open at rest.

405: Upper output terminal

406: Adjustable potentiometer or resistance Rbi1.

407: Rbs2 resistor 408: Rbi2 resistor

409: Adjustable potentiometer or resistance Rbs1.

410: Relay contacts (416), open at rest 411: Lower output terminal.

412: Relay contacts (416), closed at rest 413: Adjustable potentiometer or resistance Rai 414: Lower input terminal.

415: Relay activation input terminal (416)

416: Relay with normally closed (412) and normally open (410) contacts 417: Common terminal of relay inputs.

418: Relay with normally closed (402) and normally open contacts (404) 419: Relay activation input (418)

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PREFERRED EMBODIMENT OF THE INVENTION

For illustrative and non-limiting purposes, we detail a preferred embodiment of the invention, according to Figure 4. The system described allows two discrete control points, one in increase and one in decrease in the electric position of the cursor of a potentiometer The use of adjustable resistors allows to modify in situ the values of relative variation of the position of the potentiometer, as well as to adjust the equivalent resistance of the set to adapt to different values of potentiometers.

The end terminals of the potentiometer will be connected to the input terminals of the circuit, (401) and (414). The output terminals (405) and (411) will be connected to the points of the original control system where the end terminals of the potentiometer were inserted. The potentiometer cursor connection is not modified.

The circuit of Figure 4 includes two relays (416) and (418), with windings of adequate voltage to the specific application; typically 5V, 12V, 24V or 48V. They can be signal relays, given the low switching power required. The relay (418), which will have NC (402) and NA (404) contacts allows the insertion of the adjustable resistance Ras (403), and the parallel connection between the output terminals (405) and (411) of the group of resistors Rbs2 (407) and Rsb1 (409). The relay (416), which will have NC (412) and NA (410) contacts allows the insertion of the Rai resistor (413), and the parallel connection between the output terminals (405) and (411) of the group of resistors Rbi2 (408) and Rib1 (406).

If both relays are at rest, the parallel branches will be disconnected and the series resistors will be bridged, so that the circuit will represent a bridge for the signals at the ends of the potentiometer. If the relay (418) is activated, by applying the signal of the appropriate level between terminals (419) and (417), the adjustable series resistor Ras (403) will be inserted and the branch consisting of the fixed resistance connected in parallel Rbs2 (407) and the adjustable Rbs1 (409). The behavior of the circuit will be as described above for the basic circuit, considering that Ra = Ras, and that Rb = Rbs1 + Rbs2, producing a displacement of the electrical position of the potentiometer equivalent to moving the cursor of the same towards the end connected to the terminal (413).

Likewise, if the relay (416) is activated, by applying the signal of the appropriate level between the terminals (415) and (417), the adjustable series resistor Rai (413) will be inserted and the composite branch connected in parallel by the fixed resistance Rbi2 (408) and the

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Adjustable Rbi1 (406). The behavior of the circuit will be as described above for the basic circuit when the insertion is done in the lower branch, considering that Ra = Rai, and that Rb = Rbi1 + Rbi2, producing a shift in the electric position of the potentiometer equivalent to moving the its cursor towards the end connected to the terminal (401).

The mission of the resistors (407) and (408) is to limit the minimum resistance of the parallel branches, to prevent the resistance of said branches from being zero, thus avoiding the risk of short-circuiting the output terminals (405) and ( 411).

If both control inputs are activated simultaneously, the electrical position would be intermediate between those dictated by the values of Ras and Rai, but the equivalent resistance of the set between ends would be below the nominal potentiometer, when connecting both branches parallel at once. This situation must be avoided by the control logic of the remote or secondary control system, preventing both control inputs from being activated simultaneously. You can also implement securities that avoid it in the circuit of the invention, but they are common techniques, and have not been included to facilitate the understanding of the above.

The values of the components can be obtained from the previously stated formulas, establishing the desired maximum and minimum adjustment values for the relative variation of the electrical position, and the range of potentiometer values that you want to be able to adjust, solving the equations to find the maximum and minimum values of the components.

The example described as preferred realization is directly applicable to the remote control in docking maneuvers of motor boats equipped with control levers with potentiometer, facilitating the operation of motors and reducers from a simple remote control provided with digital outputs capable of operating the relays ( 418) and (416).

Claims (5)

5 10 fifteen twenty 25 30 35 1. System for modifying the electrical position of a potentiometer, characterized by including at least one controlled switch closed at rest (203), a controlled switch open at rest (205), and at least two fixed, variable and / or value resistors controlled, (202) and (206), connected so that, when both switches are activated, a resistance (202) is inserted in series with one of the ends of the potentiometer, modifying the resistance balance on both sides of the cursor of the potentiometer and thereby displacing the electric position of the potentiometer cursor towards the opposite end (209), and the parallel connection of another resistor (206) between the output terminals (204) and (207) occurs, allowing the resistance to be modified equivalent of the set between the ends (204) and (207), and because, with both switches inactive, the parallel resistor is disconnected, and the bridged series resistor, so that the terminals enter da are directly connected to the output, (201) with (204) and (209) with (207). 2. System according to revindication 1, characterized in that the relative variation (P '/ P) of the electric position of the potentiometer when both switches (203) and (205) are activated, taking as reference the end of the potentiometer (209) opposite to the one in which the series resistance is inserted, depends only on the value of the series resistance (Ra) and the value of the potentiometer between ends (Rc), according to the expression: (P '/ P) = Rc / (Ra + Rc ), a parallel resistance value Rb = Rc (1 + Rc / Ra) can be found, such that the equivalent resistance between output terminals (204) and (207) is the same as the potentiometer (Rc), when both are activated switches 3. System for modifying the electric position of the cursor of a potentiometer, characterized by including at least one controlled switch closed at rest (303), a controlled switch open at rest (305), and at least two fixed resistors, variable and / or of controlled value, (302) and (306), connected so that, when both switches are activated, a resistance (302) is inserted in series with one of the ends of the potentiometer, modifying the resistance balance on both sides of the potentiometer cursor and thereby moving the electrical position of the potentiometer cursor to the opposite end (309), and the parallel connection of another resistor between the input terminals (301) and (309) occurs, allowing the equivalent resistance to be modified of the assembly between the ends (304) and (307), and because, with both inactive switches, the parallel resistor is disconnected, and the bridged series resistor, of 5 10 fifteen twenty 25 30 35 so that the input terminals are directly connected to the output terminals, (301) with (304) and (309) with (307). 4. System according to any of the preceding claims, characterized in that the series and / or parallel resistors are each formed by a group of fixed and / or variable resistors and / or of controlled value, so that it is possible to establish for each group its minimum and / or maximum value, and / or modify the value of each group by adjusting and / or modifying the physical parameter that controls the value of any of its integral elements. 5. System for modifying the electric position of the cursor of a potentiometer, characterized by including two or more systems according to any of the preceding claims, which are connected in series: one following the other, and / or collapsed series: connecting the branches series in series, and grouping at least two of the parallel branches so that they are connected between the same points, to obtain multiple values of modification of the electric position of the cursor of a potentiometer, as well as the possibility of achieving modifications of the electrical position of the cursor in both directions of its movement, according to which end of the potentiometer the series resistance is inserted.