GB2046948A - Device for controlling rotation of motor for sound equipment - Google Patents

Abstract

A device for controlling the rotational speed of a motor 17 (e.g. for a record turntable or a tape recorder) comprises an instruction input device 10, 10a for supplying rotation instruction signals to a microcomputer 11 which supplies rotation control signals to means 13 for controlling rotation of the motor 17. The microcomputer 11 comprises a program logic device which receives the instruction signals from the input device 10, 10a, and a timer controlled by the logic device. The logic device repeatedly starts the timer and, upon completion of each counting operation of the timer, produces a pulse with a variable delay relative to the completion of counting. The pulses are compared with tachometer pulses from the motor in a phase locked loop 13 controlling the motor. <IMAGE>

Description

SPECIFICATION Device for controlling rotation of motor for sound equipment The present invention relates generally to rotation controlling devices for motors used in sound equipments such as record players and tape recorders.

More particularly, the invention relates to a device for controlling the rotation of a motor for sound equipment in a manner such that the rotational speed and rotational period of the motor, the pitch of an audio signal reproduced by the sound equipment, etc., can be varied as desired and with fine gradation.

For variably controlling, for example, the rotation of a so-called phonomotor for rotating the turntable of a record player, there has heretofore been a device of the following organization. This known device comprises a quartz oscillator for producing as output a reference signal of a constant frequency, a phase comparator which receives this reference signal as one input, a low-pass filter which receives the output of the phase comparator, a driving amplifier for amplifying the output of the low-pass filter and supplying the amplified output to a phonomotor, a frequency generator for generating pulses of a frequency proportional to the rotational speed of the phonomotor, and a programmable base-N counter which can preset, and which receives the pulses thus generated and supplies its output to the phase comparator as another input thereof.The initial value of the count of the base-N counter is preset when a preset button is pushed.

By the operation of this known control device, the rotational speed of the phonomotor is variably controlled in response to the variably set value of the base N of the base-N counter. For this reason, in this known device, the variable control of only the rotational speed of the phonomotor is possible by the manipulation of the preset button with respect to the base-N counter. Consequently, only the variable adjustment of the rotational speed of the record to a rotational speed as a number of percent plus or minus relative to a standard value of 333 or 45 rpm.

has been possible, and it has not been possible to variably adjust the playing time of the entire record to a desired value. Furthermore, since the pitch of a reproduced audio signal also does not have a simple relationship of linear proportionality with the rotational speed, the variable adjustment of the pitch to a desired value also has been impossible.

Another example of a known rotation controlling device of a phonomotor comprises a quartz oscillator for producing as output a reference signal of a constant frequency, a programmable base-N counter capable of being preset which receives this reference signal, a phase comparator receiving the output of this base-N counter as one input, a low-pass filter receiving the output of the phase comparator, a driving amplifier for amplifying the output of the low-pass filter and supplying the output thus amplified to a phonomotor, and a frequency generator for generating pulses of a frequency proportional to the rotational speed of the phonomotor and supplying these pulse to the phase comparator as another input thereof.

In this known device, the rotational period of the phonomotor is variably controlled in response to the variable setting of the value of the base N of the base-N counter. For this reason, in this known device, it is possible to variably control only the rotational period of the phonomotor by the manipulation of a preset button with respect to the base-N counter. Therefore, while the playing time of the entire record can be variably adjusted to a desired value, the rotational speed of the phonomotor and the pitch of a reproduced audio signal cannot be variably adjusted.

Still another problem encountered in both of the above described known devices is that, in order to obtain variable adjustments of rotational speed, rotational period, etc., in fine minute steps or gradations, the base N of the base-N counter must be made large. For this reason, the circuit parts of the base-N counter and the presetting and other parts associated therewith become complicated and expensive.

Accordingly, it is a general object of the present invention to provide a novel and useful device for controlling the rotation of a motor for sound equipment, in which device the above described problems have been overcome.

The present invention provides a rotation control device of a motor for sound equipment, comprising an instruction input device for applying instruction signals for instructing the rotational mode of a motor, a microcomputer for receiving each instruction signal from the instruction input device and producing as output a rotation control signal responsive to the instruction signal, and means for controlling the rotation of the motor in response to the rotation control signal, the microcomputer comprising a program logic device which receives each instruction signal from the instruction input device and a timer controlled by the program logic device, the program logic device operating in response to the instruction signal thus received to set and start the timer and, upon completion of counting of the timer, to produce as output the rotation control signal with a delay relative to the completion of counting, the program logic device repeating the stated operation.

Another object of the invention is to provide a rotation controlling device of a motor for sound equipment in which a microcomputer (or microprocessor) comprising a program logic device with a timer counter (timer) in place of a programmable base-N counter is used. By the use of the control device of the invention, the rotational speed and the rotational period of a motor for sound equipment or the pitch of a reproduced audio signal, etc. can be variably adjusted and controlled with fine steps or gradation.

Still another object of the invention is to provide of rotation controlling device of a motor for sound equipment in which the program logic device is capable of executing programs other than a time forming program for the purpose of generating period signals during the operation of the timer. In the operation of the controlling device of the invention, the program logic device carries out operations such as processing in response to a speed-variation command or instruction from the input part during the operational period of the timer, processing for the accompanying display, and execution of programs separate from period signal generation.

Other objects and further features of the invention will be apparent from the following detailed description with respect to preferred embodiments of the invention when read in conjunction with the accompanying drawings, in which: Figure 7 is a block diagram of one embodiment of the rotation controlling device according to the present invention of a motor for sound equipment; Figure 2 is a front view of a panel of an instruction input part 10 in the device shown in Figure 1; Figure 3 is an outline block diagram of a microcomputer part in the device illustrated in Figure 1; Figure 4 is a flow chart for a description of one example of operation of the microcomputer part in the device shown in Figure 1; and Figure 5 is a flow chart for a description of another example of operation of the microcomputer part of the device shown in Figure 1.

Referring first to Figure 1, as a result of manipulative control of an instruction input part 10, an instruction signal is sent therefrom and introduced as input into a microcomputer (or microprocessor) 11. The instruction input part 10 has a panel face 10a, for example, as shown in Figure 2. When a button 20 on this panel 10a is pushed, an instruction signal for switching the rotational speed of a turntable between 33- rpm. and 45 rpm. is sent out from the input part 10, and, at the same time, a display lamp 21 a or 21 b is lit.

If, afterthe rotational speed has been set with the button 20, a button 22, for example, is pushed, an instruction signal for increasing the rotational speed of the turntable will be sent out from the input part 10. This instruction signal is sent out as long as the button 22 is being pushed, and during this time, the rotational speed of the turntable becomes progressively high. On the other hand, while a button 24 is being pushed, an instruction signal for slowing the rotational speed is sent out from the input part 10. If a button 23 is then pushed, a signal for causing the rotational speed oftheturntableto return to the reference set speed set by the pressing of the button 20 will be sent out as output irrespective of the rotational speed which has been variably adjusted by means of the button 22 or 24.When a button 25 is pushed, an instruction signal for variable adjustment and switching of the pitch of a reproduced audio signal and the playing time of the entire record is sent out from the input part 10, and, at the same time, a display lamp 26a or 26b is lit. After the button 25 has been pushed, the variable adjustment of the pitch to a higher or lower level or the length of the playing time is carried by pushing the button 22 or 24.

For the microcomputer 11 in the present embodiment of the invention, a single-chip microcomputer MK 3870 of the MOSTEK company, for example, is used. As shown in Figure 3, this microcomputer 11 has a program logic device 30 and a timer 31 associated therewith. This program logic device has an organization comprising ordinary components such as a program ROM, ROM address register, instruction register, control logic accumulator and status register, and ALU. The instruction signal from the instruction input part 10 is introduced as input through a port 32 into the program logic device 30.

As a result of the operation, described hereinafter, of the microcomputer 11, a period signal is produced as output from a port 33 and is fed to one of the input terriiinals of a phase comparator 14 in a phaselocked loop (PLL) 13 of the device shown in Figure 1.

The output of the phase comparator 14 is supplied by way of a low-pass filter 15 to a driving amplifier 16, where it is amplified. The resulting output of this driving amplifier 16 is supplied to and drives in rotation a DC phonomotor 17 for rotating a turntable on which a record disc is placed, the rotation of the phonomotor 17 being thus controlled. Afrequency generator 18 is provided on the rotor shaft of the phonomotor 17 and generates a signal of a frequency responsive to the rotational speed of the phonomotor 17. The signal is fed to the other input terminal of the phase comparator 14. By the operation of the PLL 13 of the above described organization, the rotation of the phonomotor 17 is so controlled that it rotates at a speed responsive to signals from the microcomputer 11.

Next, one example of operation, consistuting an embodiment of the invention, of the microcomputer 11 will now be described in conjunction with Figure 4. When the power source is turned on, the microcomputer 11 is started as indicated at a step 40. At a step 41, the program logic device 30 senses the instruction signal sent from the instruction input part 10 through the port 32 and determines the presetting of the count value of the timer 31 in a step 42 and the delay time in a step 45. The timer 31 starts at the step 42, and at a step 43, a decision is made as to whether or not the count value of the timer 31 has reached the preset count value.

In the case where, as a result of the decision at the step 43, the count value of the timer 31 has not yet reached the preset count value (i.e., in the case where the decision result is "NO"), the instruction signal from the input part 10 is sensed at a step 44, and a new instruction is received. In the case where the fact that there has been a change in the content of the instruction is sensed at the step 44, the preset value of the count value of the timer 31 in the step 42 and the value of the delay time in the step 45 are changed to correspond to the content of the new instruction.

In the case where the count value of the timer 31 reaches the preset value, the above mentioned delay time determined at the step 45 is applied, and pulses are produced as output at a step 46. As a result of repetition of the above described steps, a period signal corresponding to the instruction signal from the input part 10 is obtained through the port 33 of the program logic device 30 of the microcomputer 11 and is fed to the phase comparator 14 of the above mentioned PLL 13.

The delay at the step 45 is determined by the total value of the command execution time ofthe part of the step 45 of the program. Accordingly, the setting of the delay time can be carried out with the shortest command execution time in the microcomputer as the minimum unit. The minimum unit of delay is of the order of 1 to 3y second, for example, in an ordinary microcomputer. In the device of the present invention, therefore, it is possible to carry out fine adjustment of the rotational period of a motor with 1 to 3 F seconds as a unit.

In this connection, the count value to be preset of the timer 31 is selected at a value such that, for every standard rotational speed (for example, 339 rpm., 45 rpm.) of the turntable, the counting is completed at a time value (for example, 19 m sec.) which is shorter than the rotational period (for example, 20 m sec. in the case of 33$ rpm.) corresponding to this standard rotational speed. This time difference (1 m sec. in the above case) is corrected with the delay of the step 45. In the case wherein the rotational period is made to be 19 m sec. in the above mentioned example, the deviation of the rotational speed is +5 percent relative to the standard 331 rpm., and, in the case wherein it is made to be 21 m sec. by the application thereto of a delay, the deviation is -5 percent.The rotation is variably adjusted at will within this range.

The period of the signal produced at output by the microcomputer 11 in response to the instruction signal from the input part 10 is determined by the sum of the time required by the counter 31 to count until the preset count value is reached and the set delay time. Accordingly, the program logic device 30 is idle during the time interval from the starting of the timer 31. The time interval can be effectively utilized by the operation of an embodiment of the invention as shown in Figure 5 and as described below. In Figure 5, those parts which are the same as corresponding parts in Figure 4 are designated by like reference numerals. Description of such parts will be omitted.

In the present embodiment of the invention, the parts of the steps 43 and 44 indicated by the intermittent-line enclosure in Figure 4 assumes the step sequence indicated by the intermittent-line enclosure in Figure 5. In the embodiment of the invention illustrated in Figure 4, the instruction signal is received, and operation takes place at the step 44 in the time interval up to the completion of counting of the timer 31. In the present embodiment of the invention, the device is so adapted that the operation for indication output is controlled during the above mentioned period.

At the step 42, the timer 31 is set and starts, after which, at a step 47, a decision is made as to whether or not the counting of the timer is near its completion. In the case wherein there is still some time leeway before the completion of counting of the timer, that is, in the case wherein the result of the decision at the step 47 is "NO", the operation advances to the step 44, at which the instruction signal from the input part 10 is sensed, whereby a new instruction is received, and processing thereof is carried out. Then, at a step 49, signals for indication of the rotational speed, deviation, etc., are produced as outputs, and the operation returns to the step 47.As a result of the operation of the step 49, an indication output signal is led out through a port 34 of the microcomputer shown in Figure 3 and is sent to a display device 12 in the device shown in Figure 1,where displaying of the rotational speed, deviation, etc., is effected.

In the case wherein the decision at the step 47 is that the counting of the timer 31 is near its completion, that is, in the case where the result of the decision at the step 47 is "YES", the operation advances to a step 48, and a decision is made as to whether or not the counting of the timer 31 has been completed. When the counting of the timer has not been completed, the decision operation is repeated, and when this counting is completed, the operation advances through the steps 45 and 46.

In the embodiment of the invention illustrated in Figure 4, there is a possibility of the counting of the timer 31 being completed during the operational processing at the step 44, and there are instances wherein the instant of the actual counting completion of the timer and the instant at which the program advances to the step 45 no longer coincide.

In such a case, there will arise a problem in that jitter will exist in the output period signal obtained at the step 46.

In contrast, in accordance with the present embodiment of the invention, the decision criterion at the step 47 is determined beforehand upon consideration of the processing times at the steps 44 and 49.

By this measure, there will be no delay in the detection of the instant of completion of the counting in the timer 31, and the timer for one circuit of the loop of the step 42 < steps 47, 48 step 45 < step 46 < step 42 will become constant. Therefore, an advantageous feature of this control device is that an output period signal without jitter can be easily obtained.

By the use of the control device of the present invention, variable adjustment of the rotational period in very minute steps or gradations of a unit of the order of one ten-thousandth of one period, for example, becomes possible. In a conventional device of this kind, it is necessary to use a programmable counter of very large count number and of high price in order to obtain fine variable adjustment. In contrast, the organization of the device of the present invention can be made very inexpensive.

Furthermore, in accordance with the invention, the setting of the control of the rotation of the motor is carried out by the program in the program logic device. Accordingly, the programming can be so carried out that the rotation control variably controls variables such as the rotational speed, rotational period, and the pitch of a reproduced audio signal which is substantially proportional to the logarithm of the rotational speed. For this reason, in contrast to the conventional device in which the variable control of only one variable out of the rotational speed, the rotational period, and the pitch of a reproduced audio signal is possible, it is possible in the device of the present invention to select and carry out variable control of any of these variables.

Further, this invention is not limited to these embodiments but various variations and modifica tions may be made without departing from the scope of the invention.

Claims (5)

1. A rotation control device of a motor for sound equipment, comprising: an instruction input device for applying instruction signals for instructing the rotational mode of a motor; a microcomputer for receiving each instruction signal from the instruction input device and produc ing as output a rotation control signal responsive to the instruction signal; and means for controlling the rotation of the motor in response to the rotation control signal, the microcomputer comprising a program logic device which receives each instruction signal from the instruction input device and a timer controlled by the program logic device, the program logic device operating in response to the instruction signal thus received to set and start the timer and, upon completion of counting of the timer, to produce as output the rotation control signal with a delay relative to the completion of counting, the program logic device repeating the stated operation.

2. A motor rotation control device as claimed in claim 1 in which the program logic device operates in response to a variation in the content of the instruction signal thus received to carry out opera tions such as varying the program of the program logic device, varying of data referred to by the program, and producing as output signals for dis piay responsive to these variations in the time interval from the instant of setting of the time to the instant of completion of counting of the timer.

3. A motor rotation control device as claimed in claim 1 in which the instruction input device selec tively produces as output instruction signals for variably adjusting and controlling the rotational speed and rotational period of the motor and the pitch of a reproduced audio signal, and the program logic device varies the program thereof in response to the contents of the instruction signal thus pro duced.

4. A motor rotation control device as claimed in claim 1 in which the rotation controlling means comprises a phase comparator receiving as one input thereof a rotation control signal from the microcomputer, a low-pass filter receiving the result ing output signal of the phase comparator, a driving amplifier for receiving and amplifying the resulting output signal of the low-pass filter and supplying the signal thus amplified to the motor thereby to rotationally drive and control the rotation of the motor, and a frequency generator for producing as output a signal of a frequency responsive to the rotation of the motor and supplying said output signal as another input to the phase comparator.

5. A device for controlling rotation of motor for sound equipment substantially as described with reference to the accompanying drawings.