GB2243911A

GB2243911A - Rotary control devices

Info

Publication number: GB2243911A
Application number: GB9010355A
Authority: GB
Inventors: John William East
Original assignee: Sony Corp
Current assignee: Sony Corp
Priority date: 1990-05-09
Filing date: 1990-05-09
Publication date: 1991-11-13
Anticipated expiration: 2010-05-09
Also published as: GB9010355D0; GB2243911B

Abstract

A rotary control device, such as an endless dual potentiometer arrangement 10, is provided with a knob 12 which can indicate the value of the parameter controlled by the device. The knob 12 has an array of transparent windows through which LEDs 20 can be illuminated, and a selected one is illuminated and remains illuminated during knob rotation, on the basis of control signals supplied via a slip ring/contact arrangement 24 and a serial input LED driver integrated circuit mounted on a printed circuit board 22. The illuminated LED thus acts as a pointer for the knob 12. In the case that the control device is used to control a selected one of a number of values, the appropriate LED will illuminate to indicate the corresponding value in response to selection of that value. <IMAGE>

Description

ROTARY CONTROL DEVICES This invention relates to rotary control devices, for example potentiometers.

Rotary control devices have conventionally been provided with a knob for adjustment of the control device and a pointer attached to or integral with the knob for indicating to the-user the position of the knob and thus the setting of the control device. In the case of a potentiometer used in audio equipment, for example to adjust the sound volume, the position of the knob as indicated by the pointer provides an initial indication of the degree of attenuation and thus the likely sound volume.

It is known to use rotary control devices of so-called "endless" type which, unlike conventional rotary potentiometers having a limited arc of rotation less than 3600, have no limitation on the extent of rotation. One application for such endless control devices arises in certain types of audio equipment such as audio mixing desks in which the control devices are used to control parameters such as volume or frequency characteristics. The number of separate audio channels handled by such mixing desks can nowadays be very high, and a mixing desk having a discrete set of controls for each channel would then be very large in size, cumbersome to use and expensive. It is therefore known for a number of channels to share a single set of controls so that the number of sets of controls can be reduced to the total number of channels divided by the number of channels sharing a set of controls.A channel selector is provided so that, at any one time, the controls of a set operate to adjust the corresponding parameters of only the selected channel. When the parameters for the selected channel have been set, they are stored, generally as digital values, so that those parameters continue to operate on the channel even after the channel selector has been used to render the controls effective to adjust the parameters of a different channel. In such a situation, where a control device is selectable or assignable so that it controls more than one parameter, or more than one range of values of a parameter, it is necessary that as these assignments are changed to previous settings or different parameters, the pointer of the control device should also change position accordingly.Otherwise, there would be no correspondence between the position of the pointer and the actual parameter value following an assignment change.

One way of achieving the required change of position has involved the use of motorised control devices in which, for example, each potentiometer is provided with a motor drive which changes the position to the stored previously-selected setting as soon as the potentiometer is re-assigned such as by channel selection.

Since motorised potentiometers are cumbersome, expensive and tend to be unreliable, another proposal has involved the use of control devices of endless type, which have the advantage that the knob of each control device does not need to be physically reset to a specific position on re-assignment. The pointer in this proposal is replaced by a stationary array of light emitting elements such as light emitting diodes (LEDs) set in the control panel in a line or circle around the knob of the control device. The arrangement is that, upon change of assignment of the control device, the LED closest to the previouslyset position of that assignment is illuminated. As the knob is rotated, the LEDs are individually selectively illuminated so as to "follow" the movement of the knob and thereby simulate the action of a pointer.A problem with this arrangement is that it necessarily involves a stepping effect being perceived as one LED goes off and the adjoining LED is illuminated. Thus the full resolution of the control device is not readily indicated since the perception is of a switched effect. This is a particular problem with very slight adjustments, since the operator will be unsure as to whether the adjustment has been registered unless he sees a change in LED illumination, by which time the control device may have been moved further than required.

According to the present invention there is provided a rotary control device for adjusting and indicating the value of a parameter, the control device comprising a knob mounted for rotation with respect to a mounting structure, a plurality of light emitting elements coaxially disposed about the knob for rotation with the knob, and means for illuminating a selected one of the light emitting elements depending on the value of the parameter such that the selected light emitting element remains illuminated with rotation of the knob.

In a preferred embodiment of the invention described in greater detail below, the light emitting elements are constituted by an LED array provided on the knob itself. Upon change of assignment, the nearest LED to the previously-set position of that assignment is illuminated as in the previously-proposed arrangement but, in contrast to that arrangement, when the knob is rotated to change the setting, that LED remains on constituting an illuminated pointer which moves with the full resolution of the knob, thereby completely overcoming the stepping effect apparent in the previously-proposed arrangement.

The invention will now be described by way of example with reference to the accompanying drawings, throughout which like parts are referred to by like references, and in which: Figure 1 shows a partially schematic, part sectional side view of a control device according to an embodiment of the invention; Figure 2 shows a plan view of the knob of the control device shown in Figure 1; and Figure 3 is a schematic block diagram of a circuit which can be used with the control device of Figure 1.

Referring to Figures 1 and 2, a control device is shown in the form of an endless dual potentiometer arrangement 10 which comprises a control knob 12 attached via an insulated shaft 14 to two separate potentiometers 16,18 which, in known manner for an endless device, are ganged together so as to allow continuous rotation. The potentiometers 16,18 are arranged so that, when the slider of one potentiometer is out of contact with its track, the slider of the other potentiometer will always be in contact with its track; typically, this can be achieved by rotationally displacing the two potentiometers 16,18 by an angle of 1800. As a result, the slider of at least one potentiometer will always be in contact with its track, and known processing circuitry can be provided to convert the resistance readings from the two potentiometers 16,18 into an indication of the position and/or extent of movement of the knob 12.

As shown in Figure 2, the knob 12 is preferably formed by a two shot moulded plastics housing having an opaque body with a transparent window for each of a number of (typically forty) illumination devices such as LEDs 20 preferably in the form of wire bonded LED chips which are connected to a serial input LED driver integrated circuit chip (not shown) located within the knob 12. The driver chip and the LEDs 20 are mounted on a printed circuit board 22 attached to and co-axial with the knob 12 (Figure 1), such that connection between the LEDs 20 and the driver chip is made by the conductive tracks on the printed circuit board 22.

Connections (not shown) are provided between the printed circuit board 22 and a slip ring arrangement 24 provided on the insulated shaft 14, these connections preferably running within the insulated shaft 14.

The slip ring arrangement 24 comprises the required number of (four, as shown) slip rings 26 with a corresponding number of stationary contacts 28 bearing on the slip rings 26. Connection terminals 30 are provided for the respective stationary contacts 28 for +5V, DATA, CLK (clock) and OV. The slip ring arrangement 24 allows electrical connection to be made to the knob 12 even when this is rotated.

The operation of the potentiometer arrangement 10 shown in Figures 1 and 2 is as follows. When an assigned control task is set for the potentiometer, a selected LED 20A is to be illuminated to act as a pointer. Data indicative of which LED is to be illuminated is supplied in serial form to the DATA and CLK terminals 30. The serial data is supplied via the slip ring arrangement 24 to the driver chip, in which the serial data identifies the LED to be illuminated. Power supplied via the +5V and OV terminals 30 and the slip ring arrangement 24 is accordingly switched by the driver chip to the selected LED 20A which is therefore illuminated. Even if the potentiometer knob 12 is now rotated, the same selected LED 20A will remain illuminated as long as the serial data identifying the LED to be illuminated remains the same.

Figure 3 shows a schematic block diagram of a circuit which can be used to provide the serial data for the control device of Figures 1 and 2. Referring to Figure 3, the dual potentiometer arrangement 16,18 is connected to a rotational extent calculator 32 which, in known manner, calculates the extent of rotation of the potentiometer. An output of the rotational extent calculator 32 is connected via a data selector 34 under the control of a channel selector switch 36 to a selected one of three accumulating stores ("A" to "C") 38,40,42. The outputs of the stores 38,40,42 are supplied via another data selector 44 also under the control of the channel selector switch 36 and via a data adder 46 to a serial data converter circuit 50. DATA and CLK outputs of the serial data converter circuit 50 provide the serial data to the slip ring arrangement 24 of the potentiometer arrangement 10.

Another output of the data adder 46 is connected to an input of an actual position determining circuit 48 which also receives the output from the rotational extent calculator 32. As explained below, the actual position determining circuit 48 determines the actual position of the knob 12 relative to the panel. The output of the actual position determining circuit 48 is supplied to another input of the data adder 46.

Although three accumulating stores 38,40,42 are shown by way of example, any other number of stores can be provided, depending on the number of channels to be handled by the control device. The circuit shown in Figure 3 may for example be used in an audio mixing desk, in which the channel selector switch 36 is used to select a particular channel, and the potentiometer arrangement is used to control a parameter, such as the volume or a frequency characteristic, of the selected audio channel. In practice, a single channel selector may be used to control any number of arrangements as otherwise shown in Figure 3 so that the channel selector will allow a number of control devices to be brought into effect on the selected channel.For example, in an audio mixing desk, a set of controls may include a volume control and a number of tone controls for different frequency bands, and this set would be brought into effect for a given channel by the corresponding channel selector.

The operation of the circuit shown in Figure 3 is as follows. A channel is selected by the channel selector switch 36 and the data selectors 34,44 are set correspondingly. For example, if a channel "A" is selected, the store "A" 38 is connected in circuit by the data selectors 34,44. The store "A" 38 contains data indicative of the previous setting of the control device with respect to the channel "A", and this data is supplied by the data selector 44 to the data adder 46.

The data adder 46 also receives a value from the actual position determining circuit 48, this value indicating the actual present position of the knob 12, and hence of the array of LEDs 20, relative to the panel. The output of the data adder 46 is therefore indicative of which particular LED 20 is to be illuminated, since the output is the sum of the signal from the data selector 44 (indicating the position of desired illumination with respect to the panel) and the value from the actual position determining circuit 48 (indicating the position of the knob relative to the panel). The output of the data adder 46 is converted by the serial data converter 50 into serial data form, typically (as shown) by respective signals on DATA and CLK lines.

These are then supplied via the slip ring arrangement 24 to the LED driver chip and, as previously described, the appropriate LED 20A is illuminated.

Upon rotation of the control device, outputs from the dual potentiometer arrangement 16,18 are processed in known manner by the rotational extent calculator 32 which provides an indication of the extent of rotation of the control device. This indication is supplied both to the selected store "A" 38 and to the actual position determining circuit 48. The accumulating value in the store is changed in accordance with the extent of rotation of the control device. Also, the indication of the position of the knob 12 provided by the actual position determining circuit 48 is changed in accordance with the calculated extent of rotation.Since both inputs to the data adder 46 are changing by a similar magnitude but which is arranged to be of opposite polarity, the data supplied to the serial data converter 50 and thence to the LED array remains the same and there is no change to the LED 20A which is illuminated.

When the channel selector switch 36 selects a different channel, such as channel 2'B" or channel "C", the operation will be similar to that described above, an LED being initially selected on the basis of the stored parameter value for that channel and the relative position of the knob.

The circuit in Figure 3 has been given only by way of example, and many other configurations are possible. In particular, modifications of those previously-proposed (as described above) with respect to the arrangement in which LEDs are disposed in a stationary array in the control panel are possible, as long as the appropriate circuit receives an indication of the actual position of the knob relative to the panel so that the appropriate LED in the knob can be illuminated.

It should be appreciated that the circuit of Figure 3 shows only those parts relevant to the control device selective illumination operation. Naturally, once appropriate parameter values have been set in the various stores 38,40,42, these will be effective by means of appropriate connections (not shown) to modify the actual values of the parameters in the equipment being controlled.

The invention has been described in connection with potentiometers of endless type. However, it has equal application to other control devices of this kind, particularly when each control device has multiple functions.

Claims

1. A rotary control device for adjusting and indicating the value of a parameter, the control device comprising a knob mounted for rotation with respect to a mounting structure, a plurality of light emitting elements coaxially disposed about the knob for rotation with the knob, and means for illuminating a selected one of the light emitting elements depending on the value of the parameter such that the selected light emitting element remains illuminated with rotation of the knob.

2. A control device according to claim 1, including means for making electrical contact between the rotatable knob and the mounting structure.

3. A control device according to claim 2, wherein the means for making electrical contact comprises slip rings mounted about a shaft attached to the knob, and contacts attached to the mounting structure and bearing on the slip rings.

4. A control device according to claim 1, claim 2 or claim 3, wherein the means for illuminating a selected one of the light emitting elements comprises a decoder arranged to receive serial data signals indicative of the present value of the parameter and operable to decode the serial data signals to generate an illumination signal for the light emitting element selected on the basis of the value of the parameter.

5. A control device according to claim 4, wherein the decoder is arranged to receive data and clock signals as the serial data signals.

6. A control device according to any one of the preceding claims, including storage means for storing the value of the parameter.

7. A control device according to claim 6, for use in a system having a plurality of channels, including a corresponding plurality of storage means for storing respective values of the parameter, and a channel selector for selecting one of the channels wherein the respective value stored in the corresponding storage means is supplied to the means for illuminating the selected light emitting element.

8. A control device according to any one of the preceding claims, wherein the control device is a potentiometer and the parameter is a voltage or a digital value representing a voltage.

9. A control device according to claim 8, wherein the potentiometer is of endless dual potentiometer type.

10. A control device according to claim 8 or claim 9, wherein the voltage or digital value representing a voltage is operable to control an audio function.

11. A control device according to any one of the preceding claims, wherein the light emitting elements are light emitting diodes.

12. A rotary control device substantially as hereinbefore described with reference to and as illustrated in Figures 1 and 2 or Figures 1 to 3 of the accompanying drawings.