JPH0724081B2 - Swivel-type toon-arm record end detection device - Google Patents

Description

Description: BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a record end detection device for a swing type tone arm of a record player.

2. Description of the Related Art In recent years, it has become necessary for a record player to detect the end of a record with high accuracy.

Hereinafter, an example of the conventional record end detection device of the above-described turning type tone arm will be described with reference to the drawings.

FIG. 2 shows a conventional rotary tone arm record end detecting device. In FIG. 2, reference numeral 1 is a rotating type tone arm. 2 is a rotor magnet that rotates coaxially with the swivel type tone arm; 3 is a detection coil that detects the rotational speed of the rotor magnet 2 as a back electromotive force;
Reference numeral 4 is a DC amplifier that amplifies the back electromotive force generated in the detection coil 3, 5 is a comparator that compares the output voltage of the DC amplifier 4 with a reference voltage, and 6 is an output level of the comparator 5 that is "H". For example, it is a return circuit that returns the tone arm.

The operation of the rotary tone arm record end detecting device configured as described above will be described below.

First, if the revolving tone arm 1 rotates during the performance of a record, the rotor magnet 2 rotates at the same time as the rotation, and a counter electromotive force proportional to this rotation speed is generated in the detection coil 3. This back electromotive force is amplified by the DC amplifier 4, this output voltage is compared with the reference voltage Vs of the comparator 5, and the output of this comparator causes the return circuit 6 to return the tone arm. The end of the record is 3mm with one turntable rotation
Since the tone arm moves about, Vs is set to the back electromotive force value for the speed of 2 mm / 1 rotation, for example.

Problems to be Solved by the Invention However, in the above-mentioned configuration, since the rotation speed of the turning tone arm 1 at the time of detecting the end is very slow, the counter electromotive force generated in the detection coil 3 is generally small, and the DC amplifier 4
Therefore, the voltage input to the comparator 5 is greatly affected by the offset voltage of the DC amplifier 4 and the temperature drift of the offset voltage, resulting in a problem that the termination detection is missed. there were.

In view of the above problems, the present invention is not affected by the offset voltage of the DC amplifier 4 and the temperature drift of the offset voltage, and detects the end of the record only by the amplified output of the back electromotive force of the detection coil 3. The present invention provides a recordable end detection device for a rotatable tone arm.

Means for Solving the Problems In order to solve the above problems, the record end detection device of the swivel type tone arm according to the present invention is provided after a conventional direct amplifier.
An A / D converter is provided, and the digital amount of the output of the A / D converter is input to a logic circuit.

The present invention has the above-described configuration, and first reads the amplified output of the back electromotive force when the tone arm is stationary into the logic circuit as the digital quantity n ₀ through the A / D converter, and then, during the record performance, the tone The increase of the counter electromotive force due to arm rotation is read as a digital value n through the A / D converter, and the difference (n) with the digital value when the tone arm stands still (n
Since the end of the record is determined by −n ₀ ), it is not affected by the offset voltage of the DC amplifier and the temperature drift of the offset voltage.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT A record end detecting device for a swing type tone arm according to an embodiment of the present invention will be described below with reference to the drawings.

FIG. 1 shows an end detection device for a record of a swing type tone arm according to an embodiment of the present invention. In FIG. 1, 7 is an A / D converter for A / D converting the output of the DC amplifier 4, and 8 is a microcomputer for reading the digital amount of the A / D converter 7. Others are exactly the same as in FIG.

The operation of the rotary tone arm record end detecting device configured as described above will be described below.

First, when the tone arm 1 is in the arm rest position or the like and is stationary, the counter electromotive force generated in the detection coil 3 is 0. Therefore, the output voltage of the DC amplifier 4 at that time is A /
It is stored in the microcomputer 8 as the digital amount n _{0 by the} D converter 7. Next, during the performance of the record, the output voltage of the DC amplifier 4 of the counter electromotive force generated in the detection coil 3 when the tone arm 1 is rotating is read by the A / D converter 7 as a digital amount n into the microcomputer 8. And the digital quantity n
And the digital amount n ₀ when the tone arm is stationary (n-
It is determined whether the tone arm has reached the end of the record by n ₀ ), and when (n−n ₀ ) n ₁ , the return circuit 6
To return the tone arm.

n ₁ is set to a digital amount for a speed of 2 mm / 1 rotation, for example.

As described above, according to this embodiment, the output of the DC amplifier 4 during record performance is converted into a digital amount by the A / D converter 7, and the digital amount is read by the microcomputer 8 to obtain the digital amount when the tone arm is stationary. By detecting the end point based on the difference from n ₀ , the influence of the offset voltage of the DC amplifier 4 and the temperature drift of the offset voltage can be removed, and the end point of the record can be detected by the highly accurate speed detection of the tone arm.

As described above, according to the present invention, the amplified output of the DC amplifier of the counter electromotive force generated in the detection coil in proportion to the rotational speed of the magnet coaxial with the tone arm during record performance is digitalized by the A / D converter. Offset to the offset of the DC amplifier by detecting the end of the record from the difference (n-n ₀ ) with the same digital amount n ₀ when the tone arm is stationary and the digital amount n is read by the microcomputer. It is possible to detect the end of the record by highly accurately detecting the speed of the tone arm by removing the influence of the voltage and the temperature drift of the offset voltage.

[Brief description of drawings]

FIG. 1 is a block diagram of an end detection device for a record of a swing type tone arm according to an embodiment of the present invention, and FIG. 2 is a block diagram of one detection device for a record of a swing type tone arm of the related art. 1 ... tone arm body, 2 ... rotor magnet,
3 ... Detection coil, 4 ... DC amplifier, 5 ... Comparator,
6 ... Return circuit, 7 ... A / D converter, 8 ... Microcomputer.

Claims (1)

[Claims] 1. A revolving tone arm, a rotor magnet mounted coaxially with a rotating shaft of the revolving tone arm, a detection coil for detecting a rotation speed of the rotor magnet as a back electromotive force, and a detection coil of the detection coil. A DC amplifier that amplifies the back electromotive force and an amplified output of the DC amplifier
It has an A / D converter for A / D conversion, a logic circuit for reading the digital amount of the output of the A / D converter, and a return circuit for returning the tone arm. The speed of the end of the record is detected based on the difference between the digital amount of the amplified output of electric power and the digital amount of the amplified output of the counter electromotive force when the tone arm is rotating. Record end detector.