GB2406944A

GB2406944A - Keyboard switching devices

Info

Publication number: GB2406944A
Application number: GB0323614A
Authority: GB
Inventors: Yona Newman
Original assignee: Motorola Inc
Current assignee: Motorola Solutions Inc
Priority date: 2003-10-09
Filing date: 2003-10-09
Publication date: 2005-04-13
Also published as: GB0323614D0

Abstract

A switching device has a source of radiation 602,604; a button or key 601 operable by a user, and a sensor 606,607 operable to detect if the radiation has been blocked, or deflected, by operation of the button 601. In one form the device may include a matrix array of such keys or buttons and one or more rows of light sources and corresponding detectors.

Description

1 2406944 TITLE: SWITCHING DEVICES r

Field of the Invention

The present invention relates to switching devices.

In particular, it relates to switching devices for use in handsets such as mobile wireless communications terminals having an interface for accepting user entered messages or instructions.

Background of the Invention

Keypads or keyboards used in battery operated handsets such as Portable Data Terminals (PDTs) and Personal Digital Assistants (PDAs) and mobile telephones and radios normally include a plurality of user operated switches to allow user operated information and instructions to be entered in the handset. Such switches conventionally include a button or key, e.g. made of a moulded plastics material, which when depressed causes electrical contact to be made between two conducting members thereby closing a switch in a circuit. In some cases, one of the conducting members is one of a series of conducting lines or strips in a matrix of lines or strips. The matrix is scanned by applying a logic signal sequentially to each of the lines along one axis of the matrix while inputting simultaneously all the states of the lines on the other axis of the scan matrix as determined by whether a button or key on that line is operated.

The present inventor has appreciated that switching devices made in a known manner as described above have a number of disadvantages. Electromechanical switches of the kind described, e.g. when used in a keypad or keyboard, occupy discrete space which can only be used for this function and the space is not available for any other function.

Also, since the contacts close circuits to produce electrical signals, making an intrinsically safe key assembly for use in a hazardous environment, e.g. an atmosphere in which an explosion can be caused by an electrical signal, is very difficult.

Also, since the contacts must make an electrically conductive circuit when operated, effects such as oxidization, erosion, and dirt and dust ingress cause the known switch to have a high resistance over a period of time and therefore to fail.

Summary of the Invention

In accordance the present invention, there is provided a switching device according to claim l of the accompanying claims. The switching device may have the features of any one or more of accompanying claims l 16.

The invention shows the following benefits compared

with the prior art. Radiation beams such as light

(laser) beams can be transmitted through air, water or solids so the switching device can be fully environmentally sealed and operational in any medium, e.g. under water. No exposed electrical contacts are required so the invention is intrinsically safe for use in hazardous environments such as explosive atmospheres. Styling, size, length of travel and pressure of the key button are independent of the switching mechanism so can be freely varied by the equipment designer without any undue constraints. Some of the surface area under key buttons is not necessarily used and so is available for other functions.

Embodiments of the present invention will now be described by way of example with reference to the accompanying drawings, in which:

Brief description of the drawings

FIG. l is a somewhat schematic prior art keyboard

arrangement included in a communications handset.

FIG. 2 is a schematic top view and FIG. 3 is a schematic sectional side view of a switching device embodying the invention.

FIG. 4 is a schematic top view and FIG. 5 is a schematic sectional side view of the device of FIGs. 2 and 3 in operation.

FIG 6 is an underside view of a button used in the switching device of FIGs. 2 to 5.

FIG 7 is a side perspective view of the button of FIG. 6.

FIG. 8 is a schematic top view of an alternative switching device embodying the invention.

FIG. 9 is a schematic top view of the device of FIG. 6 in operation.

FIG. lO is an underside view of a button used in the switching device of FIGs. 2 and 3.

FIG It is a side perspective view of the button of FIG. lO.

FIG. 12 is a somewhat schematic top view of a matrix switching device embodying the invention based on the device of FIGs. 8 to 11.

FIG. 13 is a schematic matrix switching arrangement S embodying the invention based on the device of FIGs. 2 to 7.

FIG. 14 is a schematic matrix switching arrangement embodying the invention based on the device of FIGs. 8 to 11.

FIG. 15 is a schematic self testing matrix arrangement embodying the invention based on the arrangement of FIG. 13.

Description of embodiments of the invention.

FIG. 1 shows a conventional form of keyboard arrangement 100 used in a communications handset, e.g. for wireless data communication. A series of buttons 102 (keys) is provided on a keyboard. Each button when depressed by a user provides electrical contact with a printed circuit board 101 in a region beneath the button. A circuit containing the selected button is therefore closed causing the selected button and closed circuit to be recognized by processing circuitry of the handset and for an appropriate function to be applied, e.g. entry of an alphanumeric character associated with the button to be made. The button therefore provides a user selected electro-mechanical switch which enables a function of the handset to be selected.

One way in which the processing circuitry may recognise that a selected button has been depressed is to arrange the buttons in a row and column matrix with contact conductors, on the printed circuit board 101 beneath the buttons, running along rows and columns whereby the row and column matrix position of the selected button may be detected. For example, the conductors may be scanned by outputting from control electronics 103 via a connection 105 a logic signal sequentially on each of a series of the conductors (not shown) running along one axis of the matrix (e.g. along rows) while inputting simultaneously all the states of the conductors (not shown) running along the other axis (e.g. columns) via a connection 104. The conventional arrangement shown in FIG. 1 shows the problems mentioned earlier.

FIGs. 2-7 show a simple form of switching device embodying the invention. As seen in top view in FIG. 2, the device includes a light source 201 such as a semiconductor pen junction laser diode of the kind commonly used in reading of information stored on compact discs. The source 201 generates and emits a light beam 202 which is directed toward a button 203. A light detector 204 in the same horizontal plane as the light source 1 and the button 203 is positioned on an axis passing also through the button 203 which axis is perpendicular to the beam 202.

FIG. 3 is a schematic sectional side view of a vertical plane passing through the beam 202. The printed circuit board 101 is also seen in FIG. 3. The light source 201 is electrically connected to the printed circuit board. When the button 203 is not depressed, the button 203 remains above the beam 201 and the beam 201 passes in a straight line beyond the button 203 and does not reach the detector 204 (shown dashed in FIG. 3 as it out of the plane of the drawing), so no light input is detected at the detector 204. The detector 204 produces a '0' electrical output.

When the button 203 is depressed by the finger of a S user, the beam 203 is reflected, as seen in FIGs. 4 and 5, by the button 203 toward the light detector 204 and a light input is therefore detected by the detector 204.

The detector 204 produces a '1' electrical output signal. As seen in FIG. 5, the reflection is caused by the beam 202 striking the button 203 when the button 202 is depressed. FIG. 6 and FIG. 7 show that the button 203 carries on its underside a prism 205 having a front reflecting surface 206 which the beam 202 IS strikes at an angle of 45 degrees providing the required reflection toward the detector 204.

FIGs. 8-11 show another simple form of switching device embodying the invention. As seen in schematic top view in FIG. 8, the device includes a button 601 and a light source 602 which generates and emits a light beam 603 which is directed toward the button 601 along a first axis (the horizontal axis as seen in the plane of FIG. 8). The device also includes a light source 604 which generates and emits a light beam 605 which is directed toward the button 603 along a second axis perpendicular to the first (i.e. the vertical axis as seen in the plane of FIG. 8). A light detector 606 in the same horizontal plane as the light source 602 and the button 601 (the plane of the drawing) is positioned on the first axis. A light detector 607 in the same horizontal plane as the light source 604 and the button 601 (the plane of the drawing) is positioned on the second axis.

When the button 601 is not depressed, the button 601 remains above the beams 603, 605 and the beams 603, 605 pass in a straight line beyond the button 601 to reach the detectors 606 and 607 respectively as shown in FIG. 8. Thus, a light input is detected at each of the detectors 606 and 607. Each of detectors 606 and 607 produces a 'O' electrical output signal accordingly ('0' indicating no selection of a button).

When the button 601 is depressed by the finger of a user, each of the beams 603 and 605 strikes the button 601, and is blocked by the button 601 as seen in FIG. 9. No light input is therefore detected by either of the detectors 606, 607. Each of the detectors 606, 607 now produces a '1' electrical output signal.

FIG. 10 and FIG. 11 show that the button 601 carries on its underside an opaque cylinder 608 which provides the required blocking of the beams 603, 605.

The switching device described above with reference to FIGs. 8 to 11 may be used to provide the basis of a matrix switching arrangement embodying the invention.

Such a simple arrangement is shown in FIG. 12. The arrangement includes buttons 701, 702, 703 and 704 in a row and column matrix. A light source 705 generates and emits a light beam 706 which is directed toward the buttons 701 and 702 along a first axis. A light source 707 generates and emits a light beam 708 which is directed toward the buttons 703 and 704 along the first axis. A light source 709 generates and emits a light beam 710 which is directed toward the buttons 701 and 703 along a second axis perpendicular to the first axis. A light source 711 generates and emits a light beam 712 which is directed toward the buttons 702 and 704 along the second axis. A light detector 713 in the same horizontal plane as the light source 705 and the buttons 701, 702 (the plane of the drawing) is positioned on the first axis beyond the button 702 to detect the beam 706 if not blocked by the button 701 or by the button 702. A light detector 714 in the same horizontal plane as the light source 707 and the buttons 703, 704 (the plane of the drawing) is positioned on the first axis beyond the button 704 to detect the beam 708 if not blocked by the button 702 or by the button 704. A light detector 715 in the same horizontal plane as the light source 709 and the buttons 701, 703 (the plane of the drawing) is positioned on the second axis beyond the button 703 to detect the beam 710 if not blocked by the button 701 or by the button 703. A light detector 716 in the same horizontal plane as the light source 711 and the buttons 702, 704 (the plane of the drawing) is positioned on the second axis beyond the button 704 to detect the beam 712 if not blocked by the button 702 or by the button 704.

When none of the buttons 701-704 is depressed, as shown in FIG. 12, each of the detectors 713-716 receives a light input and produces a 'O' electrical output signal. When one of the buttons 701-704 is depressed, that button blocks the light beams which are directed at that button along both the first and second axes. For example, when the button 701 is depressed, no light input is received by the detectors 713 and 715.

Thus, a '1' output from one of the detectors 713, 714 and a '1' output from one of the detectors 715, 716 indicates that a button has been depressed and the particular combination of light detectors which is producing these two outputs indicates the matrix S position of the depressed button.

Figure 13 shows an addressing implementation of a 4 x 4 matrix using reflecting switches of the kind described above with reference to FIGs. 2 to 7. The matrix includes buttons 801 to 816 arranged in rows and columns. Light sources 817 to 820 direct light beams along each of the rows. Detectors 825 to 828 are arranged to detect light beams reflected along the respective columns. Control electronics 829 has four active row output lines 830 to 833, which are sequentially energised to power each one of the four light sources 817 to 820 in turn. The output state of (any output signal from) each of the detectors 825 to 828 is sensed in turn and is fed to the control electronics 829 via an input 834.

It can be seen that if the button 803 is depressed, the light beam from the source 817 is reflected by the reflector of the button 803 toward the detector 827.

Thus, a '1' output signal will be read only at the detector 827 and only when the line 830 to the light source 817 is energized.

The light source array may be energised by output signals from standard logic circuitry and the light detectors may output standard logic level signals. This allows the control electronics 829 to be a standard matrix key scan circuit as used in the prior art, such as a keypad port on a microprocessor or a specialised keyboard scan and decoder chip.

Figure 14 shows an addressing implementation of a 4 x 4 matrix using blocking switches of the kind described above with reference to FIGs. 8 to 11. The matrix includes buttons 901 to 916 arranged in rows and columns. Light sources 917 to 920 direct light beams along each of the rows of buttons. Light sources 921 to 924 direct light beams along each of the columns of buttons. Detectors 925 to 928 are arranged to detect light beams transmitted along the respective rows.

Detectors 929 to 932 are arranged to detect light beams transmitted along each of the respective columns.

Control electronics 933 has four active row output lines 934 to 937, which are sequentially energised to power each one of the four light sources 917 to 920 in turn. Control electronics 933 has four active column output lines 938 to 941, which are sequentially energised to power each one of the four light sources 921 to 924 in turn. The output state of each of the detectors 925 to 928 and the detectors 929 to 932 is sensed in turn and is fed to the control electronics 933 via inputs 942 and 943. The receipt at the control electronics 933 of a '1' input signal on the input line 942 and a '1' input signal on the input line 943 indicates depression of a button and the position of the button in the matrix by sensing at the control electronics 933 of which one of the row detectors 925 to 928 and which one of the column detectors 929 to 932 produced the '1' output. For example, when the button 903 is depressed and the sources 917 and 923 are energised via the output lines 934 and 940, the detectors 925 and 931 will produce the '1' outputs.

Again, the light source array may be energised by output signals from standard logic circuitry and the light detectors may output standard logic level signals. This allows the control electronics 933 to be a standard matrix key scan circuit as used in the prior art, such as a keypad port on a microprocessor or a specialised keyboard scan and decoder chip. Rather than scanning the light sources 917 to 920 and 921 to 924 with an output voltage to energise them, all of the sources of one or both rows may be energized together, but scanning is less power consuming.

The matrix of buttons providing blocking switches as shown in FIGs. 12 and 14 is inherently self-testing because a signal is always received in the normal, no button depressed, state. This enables the functioning of the light sources and light detectors to be automatically tested by the control electronics.

The matrix of buttons providing reflecting switches of the kind shown in FIG. 13 can be made self-testing by adding another row of light detectors opposite the light sources, i.e. at the end of each row. Such an arrangement is shown in FIG.15 where items with the same reference numerals as in FIG. 13 have the same function and operation. In FIG. 15, the additional detectors are labelled 821 to 824. These are connected to the control electronics 829 via an input line 835.

Each light source 817 to 820 and its corresponding row of button switches may be tested by energising the light source and detecting light for the source at the corresponding light detector of the same row. Note that only one common status input signal from the control electronics 829 is required sequentially at each output line 830 to 833, since energising each light source sequentially can produce a '1' output signal only by its opposite, associated light detector.

Claims

Claims 1.A switching device including a source for producing a beam of

radiation; a button or key operable by a user to change a transmissivity property of the beam produced by the source; and a sensor operable to detect a change in a transmissivity property of the beam.
2.A switching device according to claim 1 wherein the button or key is operable to present to the beam produced by the source a surface which deflects or reflects the beam.
3.A switching device according to claim 1 wherein the button or key is operable to present to the beam produced by the source a surface which blocks the beam.
4.A switching device according to claim 1, claim 2 or claim 3 wherein the sensor is arranged to detect the beam when the button or key is not operated.
5.A switching device according to claim 1, claim 2 or claim 3 wherein the sensor is arranged to detect the beam when the button or key is operated.
6.A switching device according to any one of claims 3 to 5 which includes a plurality of sources each operable to produce a beam of radiation and the button or key is operable to present to the beam produced by each of the sources a surface which blocks the beam.
7. A switching device according to claim 6 which include a plurality of sensors wherein each of the sensors is arranged to detect a corresponding one of the beams when the button or key is not operated.
8.A switching device according to claim 2, 4 or 5 which includes a plurality of sources each operable to produce a beam of radiation and the button or key is operable to present to the beam produced by each of the sources a surface which reflects or deflects the beam.
9. A switching device according to claim 2, 4 or 5 which include a plurality of sensors wherein each of the sensors is arranged to detect a corresponding one of the beams when the button or key is not operated.
10. A switching device according to any one of the preceding claims which includes a plurality of keys or buttons arranged in a row and column matrix each of the rows and/or columns having an associated sensor.
11. A switching device according to claim 10 which includes a signal processing circuit connected to the sensors, the signal processing circuit being operable to detect which of the sensors has produced an output caused by user operation of one of the keys or buttons.
12. A switching device according to any one of claims 6 to 11 which includes a source energising circuit for providing an energising voltage to the sources in a scanned sequence.
13. A switching device according to any one of claims 8 to 12 wherein the device has a self testing mode wherein operation of the sources and/or the detectors is tested without operation of a key or button by a user.
14. A switching device according to any one of the preceding claims wherein the or each source comprises a light source and the or each sensor comprises a light detector.
15. A switching device according to claim 14 wherein the or each light source comprises a semiconductor light emitting device.
16. A switching device according to claim 15 wherein the or each light source comprises a semiconductor light emitting laser device.
17. A switching device according to any one of the S preceding claims and substantially as herein described with reference to any one or more of FIGs. 2 to 15 of the accompanying drawings.