GB2249446A - Coarse and fine adjustment of electrical apparatus by pulse generator - Google Patents

Abstract

There is disclosed an electrical apparatus, typically a radio, having an adjustable operating parameter, such as frequency in which an input means selects a desired change in the parameter; movement responsive means, such as an optical shaft encoder, provides electrical pulses and control means such as a microprocessor adjusts the parameter by a predetermined amount for each predetermined number of pulses and operates to change the relationship between the predetermined amount and number to change the resolution of the input means. <IMAGE>

Description

Electrical Apparatus Having an Adjustable Operating Parameter This invention relates to electrical apparatus having an adjustable operating parameter.

Typical of such electrical apparatus is a radio receiver, the adjustable operating parameter being the tuning frequency of the radio. The frequency is often adjusted by means of a tuning control in the form of a wheel or knob placed on the front of the radio.

It is desirable to provide the most convenient mode for the operator to interface with the functions of the radio via the control wheel so as to minimize the time required to achieve a desired change in the frequency.

The resolution of the tuning control is the minimum movement required by the control, (in the case of a wheel, angle of rotation), required to cause a change in the particular parameter which is being controlled.

Hitherto resolution of the control has been a fixed value which inevitably is a compromise of user requirements.

This invention seeks to provide an improved apparatus which is more user friendly than that of the prior art.

According to the invention there is provided electrical apparatus having an adjustable operating parameter the apparatus comprising moveable input means for selecting a change in the parameter; means responsive to movement of the input means for providing an electrical signal, control means responsive to the signal for adjusting the parameter, the control means being operable to change the relationship between the signal and the adjustment whereby to change the resolution of the input means The means for providing an electrical signal conveniently provides electrical pulses and the control means is responsive to adjust the parameter by a predetermined amount for each predetermined number of pulses1 the control means being operable to change the relationship between the predetermined amount and the predetermined number to change the resolution of the input means.

Preferably the moveable input means is a rotatable member and the means responsive to movement of the moveable input means is an optical shaft encoder coupled to the rotatable member to provide the pulses in response to rotation of the member.

In one embodiment of the invention the control means is responsive to the pulse repetition rate to change said relationship in dependence upon the pulse repetition rate.

In another embodiment the relationship between the predetermined amount and the predetermined number is selectable from a set of predetermined values by operator controllable means.

The electrical pulses may comprise two pulse trains the control means being operative to control the sense of the change of the parameter in dependence upon the relative phase of the two pulse trains.

The control means is conveniently a programmed microprocessor.

The electrical apparatus is typically radio apparatus and the adjustable operating parameter may be the tuning frequency, channel selection, manual R.F. gain, notch filter frequency and clarifier tuning.

The electrical apparatus may be a signal generator, the adjustable operating parameter being signal frequency.

An exemplary embodiment will now be described with reference to the Figure of the drawing which illustrates one embodiment of an electrical apparatus in accordance with the invention.

Referring to the drawing there is shown an electrical apparatus in the form of a radio apparatus. The radio apparatus comprises a moveable input means in the form of a rotatable tuning wheel 1 which is coupled to drive means for producing electrical pulses. in this embodiment an optical shaft encoder 2.

The optical shaft encoder has two output channels, each of which produces a train of pulses. typically 500 for each complete revolution of the tuning wheel 1. The relative phase between the two pulse trains is dependent upon the direction of rotation of the tuning wheel 1.

The two pulse trains are fed to a control means 3 in the form of a microprocessor, typically a Motorola 68HCll. Also coupled to the microprocessor 3 is operator controllable means in the form of user input 4, which is typically a multi-position switch or keypad.

The microprocessor 3 is coupled to radio tuning means 5 which conveniently includes a digitally controlled synthesizer.

In operation, rotation of the tuning wheel 1 is encoded by the optical shaft encoder to produce a pulse train on each of its two output channels. The direction of rotation of the tuning wheel, indicative of a selected increase or decrease in desired tuning frequency, is indicated by the relative phase of the two pulse trains, i.e. a first channel leads the second channel by 900 or vicc-versa.

The microprocessor 3 determines the direction of rotation from the relative phase of the two channels. The microprocessor then counts the number of pulses occuring in fixed time intervals and determines the desired frequncy change which is fed to the radio tuner 5 to adjust its frequency by digital control of its frequency synthesizer.

Two modes of operation are possible for adjustment of the resolution of the frequency control, an automatic mode and a manual mode, selectable by means of the multi position switch user input 4. If the microprocessor 3 is programmed by the switch 4 to operate in the automatic mode, the speed of rotation of the tuning wheel is determined by measurement of the pulse repetition rate.

The repetition rate is measured by the microprocessor by counting the number of pulses occuring during a fixed time period e.g. 200 ms.

The microprocessor then selects an appropriate one of a plurality of relationships between the amount of frequency adjustment of the radio tuner per predetermined number of pulses counted: Typically four resolutions are provided as shown in table 1 below: Table 1 Pulses Per Frequency Change Speed 100 msec Per Rotation 1 up to 40 1 khz 2 40 to 80 1 Okhz 3 80 to 160 100khz 4 more than 160 1Mhz Thus, as can be seen fine tuning is enabled at low speed of rotation of the tuning wheel and course tuning is provided at a high speed of rotation, consequently enabling a desired tuning frequency to be set in optimal time.

In a second mode of operation, the microprocessor 3 is programmed to operate in any one of a plurality of selectable predetermined resolutions by setting the user input 4 in one of a plurality of manual mode positions. Typically there are four manually selectable resolutions as shown in table 2 below: Table 2 Steps Per Resolution Number of Pulses Resolution Rotation Degrees Per One Step 1 5 72 100 2 10 36 50 3 15 24 33 4 100 3.6 5 A chosen frequency change may correspond to each step.

A user may thus use switch 4 to select one of four resolutions to suit his operation of the radio apparatus.

The steps performed by the microprocessor program will now be described in more detail: Program operation:- The Microproccssor Program uses 3 different interrupts: 1. for finding tuning wheel direction 2. for counting time periods of 200 msec during which pulses produced by tuning wheel rotation are counted 3. pulse counter which counts pulses produced by tuning wheel rotation Initialize all tuning wheel Darameters:- wheel direction - none wheel pulse count - 0 initialize timer for counting 200 msec initalize input capture for sensing tuning wheel direction initialize pulse counter execute the following steps: step 1: Check if the 200 ms time period passed.

If no - continue checking tuning wheel rotation direction and counting pulses.

If yes - go to step 2.

step 2: Decide about current wheel direction by majority count.

Compare the current direction to previous direction of the tuning wheel.

If same - add currcntly counted pulses to previous pulse count, otherwise subtract.

Save result in wheel-pulse-count register.

Save the wheel-direction.

stcp3: Find tuning wheel speed rotation according to wheel-pulse count and then go to table 1.

step 4: If currently controlled parameter is not frequency or if the microprocessor is programmed to work in selectable resolution mode - go to step 6.

Otherwise go to step 5.

step 5: This step is performed only during frequency changing in automatic mode.

Activate the frequency change according to tuning wheel speed of rotation, direction, wheel-pulse-count and table 1.

Initialize counters and continue to step 1.

step 6: Check if the required number of pulses per one frequency step according to selected resolution have occured per table 2.

If no - continue to step 7.

step 7 Activate the parameter change according to wheel-pulse count, direction of tuning wheel rotation and selected resolution.

Initialize counters and continue to step 1.

The invention has been described by way of example and modifications may be made without departing from the scope of invention; for example, sensed changes in an analogue signal may equally be used to initiate a change in the resolution. The invention may equally well be applied to the adjustment of channel, gain control, clarifier filters and notch filters and is also applicable to signal generators.

Claims (11)

Claims

1. Electrical apparatus having an adjustable operating parameter the apparatus comprising moveable input means for selecting a change in the parameter; means responsive to movement of the input means for providing an electrical signal, control means responsive to the signal for adjusting the parameter, the control means being operable to change the relationship between the signal and the adjustment whereby to change the resolution of the input means.

2. The apparatus of claim 1 wherein the means for providing an electrical signal provides electrical pulses and the control means is responsive to adjust the parameter by a predetermined amount for each predetermined number of pulses, the control means being operable to change the relationship between the predetermined amount and the predetermined number to change the resolution of the input means.

3. The apparatus of claim 2 wherein the moveable input means is a rotatable member and the means responsive to movement of the moveable input means is an optical shaft encoder coupled to the rotatable member to provide the pulses in response to rotation of the member.

4. The apparatus of any claim 2 or 3 wherein the control means is responsive to the pulse repetition rate to change said relationship in dependence upon the pulse repetition rate.

5. The apparatus of any one of claims 2 to 4 wherein the relationship between the predetermined amount and the predetermined number is selectable from a set of predetermined values by operator controllable means.

6. The apparatus of any one of claims 2 to 5 wherein the electrical pulses comprise two pulse trains the control means being operative to control the sense of the change of the parameter in dependence upon the relative phase of the two pulse trains.

7. The apparatus of any preceding claim wherein the control means is a programmed microprocessor.

8. The apparatus of any preceding claim and comprising radio apparatus.

9. The apparatus of claim 8 wherein the operating parameter is tuning frequency.

10. The apparatus of any preceding claim wherein the electrical apparatus is a signal generator, the adjustable operating parameter being signal frequency.

11. Electrical apparatus substantially as herein described with reference to the drawing.