JPS5852879Y2 - Chiyokuryuu Motorano The Tsuonjiyokiyo Cairo - Google Patents

Description

[Detailed Description of the Invention] The present invention relates to a noise removal circuit for a driving DC motor of an educational tape recorder in which the driving DC motor is controlled by operation on a teacher's adjustment wheel, for example.
In particular, the noise caused by the governor of the DC motor can be effectively removed.

FIG. 1 shows an example of a conventionally used educational tape recorder and a teacher's adjustment console for controlling the same, where 1 is a drive circuit for the educational tape recorder, and 2 is the teacher's adjustment console.

In this teacher's adjustment console 2, M is a microphone for the teacher, a signal from this microphone M is supplied to a preamplifier 3, and a signal amplified by this preamplifier 3 is output to an output amplifier 4. The teacher's voice is supplied to the speaker 5 (or earphone) via the speaker 5, and the teacher's voice is emitted from the speaker 5 toward the students.

Further, the signal such as the teacher's voice amplified by the preamplifier 3 is supplied to the recording magnetic head 8 of the tape recorder via the variable resistor 6 and the output amplifier 7 and is recorded. Voices etc. can be played repeatedly.

Further, in the teacher's adjustment console 2, reference numeral 9 is a DC power supply, and the positive terminal of this DC power supply 9 is connected to the power line of the preamplifier 3, and the output amplifier 7 of the tape recorder is connected via the power switch 10. It is connected to a power supply line, and the negative pole of this DC power supply 9 is connected to the common terminal of the preamplifier 3 and the output amplifier 7, respectively.

In addition, in the drive circuit 1 of a tape recorder for students, 1
1 is a drive motor for a tape recorder, and this motor 11
One end of the motor 11 is connected to the power supply line through a resistor 12 and to a common terminal through a capacitor 13. The other end of the motor 11 is connected to the collector of an npn transistor 14, and the emitter of this transistor 14 is is grounded, the base of this transistor 14 is connected to the common terminal via a resistor 15, and this base is further connected to the power supply line via a series circuit of resistors 16 and 17, and The connection point is connected to a common terminal via a control switch 18 provided on the teacher's adjustment console.

In such a configuration, the drive motor is controlled by keeping the power switch 10 in a closed state and opening and closing the control switch 18.

That is, when the control switch 18 is open, the transistor 1
4 is on, the remoter 11 is driven.

Next, when this control switch 1B is closed, the resistor 1
The potential at the connection point between 6 and 17 becomes the same potential as the common terminal, turning off the transistor 14 and stopping the motor 11.

However, in the case of this conventional tape recorder, when the control switch 13 is left open and the power switch 10 is closed to rotate the drive motor 11 of the tape recorder, the governor that adjusts the speed of the motor starts working. As a result, noise as shown in the curve in Figure 2 is generated at the connection point between the motor 11 and the resistor 12, and this noise is supplied to the amplifiers 3 and 7 through the power line and common terminal. , this amplifier 3 and T were adversely affected.

In view of the above-mentioned points, the present invention is designed to effectively eliminate noise caused by the governor of the motor, etc.

Hereinafter, an example of a DC motor noise removal circuit according to the present invention will be described with reference to FIG. 3. Parts similar to those in FIG. 1 are denoted by the same reference numerals, and detailed explanation thereof will be omitted.

In the present invention, the drive circuit 1 of the tape recorder shown in FIG. 1 is constructed as follows.

That is, the power line and the common terminal are respectively connected to the power line and the ground line of the amplifier 19, and the signal obtained at the connection point between the motor 11 and the resistor 12 is supplied to the input of the amplifier 19. The signal obtained at the output of the filter 19 is supplied to the base of the transistor 14 via a capacitor 20.

In this case, an amplifier 19 is used in which the input signal and the output signal are in phase.

The rest of the structure is the same as the example in FIG.

With this configuration, for example, when a noise signal as shown in the curve in FIG. 2 is generated at the connection point between the motor 11 and the resistor 12, this noise signal is supplied to the amplifier 19, A signal amplified in phase with the noise signal is obtained on the output side of the amplifier 19, and this signal is amplified by the transistor 14.
supplied to the base of

Since the signal obtained at the collector of this transistor 14 is in opposite phase to the signal supplied to the base, the motor 11
The noise signal from the governor etc. will be canceled out.
The adverse influence of this noise signal on the amplifiers 3 and 7 can be removed.

Therefore, according to the present invention, since the noise generated by the DC motor 11 can be effectively removed, it is possible to create a system in which the power supply line and the ground line for the DC motor are shared without any problems.

Note that the present invention is not limited to the above-described embodiments, and various other configurations may be adopted without departing from the spirit of the present invention.

[Brief explanation of the drawing]

Fig. 1 is a connection diagram showing an example of a conventionally used educational tape recorder, Fig. 2 is a diagram for explaining the present invention, and Fig. 3 is an example of a DC motor noise removal circuit according to the present invention. FIG. 11 is a motor, 12.15, 16.17 is a resistor, 13
．． 20 is a capacitor, 14 is a transistor, and 19 is an amplifier.

Claims (1)

[Scope of utility model registration request] One end of the DC motor is connected to one side of the power supply through a first resistor and the other side of the power supply through a first capacitor, the other end of the DC motor is connected to the collector of the transistor, and the other end of the DC motor is connected to the collector of the transistor. The emitter of the transistor is connected to the other power source, the base of the transistor is connected to one and the other of the power sources through second and third resistors, respectively, and the motor and the first resistor are connected to each other. The connection point is connected to the base of the transistor through an amplifier and a second capacitor, and the noise signal generated by the motor obtained at the connection point between the motor and the first resistor is amplified in phase. A DC motor noise removal circuit configured to remove the noise signal by supplying it to the base of the transistor.