JPH0724082B2 - 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 detection 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 5 causes the return circuit 6 to return the tone arm. Since the end of the record moves about 3 mm with one turn of the turntable, Vs is set equal to the counter electromotive force value for the speed of 2 mm / 1 turn, for example.

Problems to be Solved by the Invention However, in the above-described configuration, the speed of the turning type tone arm at the time of detecting the terminal end is very slow, and therefore the detection coil 3 is used.
Since the back electromotive force generated in the DC amplifier 4 is generally small and the amplification degree of the DC amplifier 4 is very high, the voltage input to the comparator 5 is affected by the offset voltage of the DC amplifier 4 and the temperature drift of the offset voltage. However, there was a problem in that it was greatly affected and missed the end detection.

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 can detect 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 record end detection device for a rotary tone arm.

Means for Solving the Problems In order to solve the above-mentioned problems, a record termination detection device of a swivel type tone arm according to the present invention includes a fixed resistor having the same resistance value as that of a detection coil before a conventional DC amplifier. , A switch for switching the connection between the fixed resistor or the detection coil and the DC amplifier, and an A / D converter after the DC amplifier are provided, and when the fixed resistor and the DC amplifier are connected by the switch,
The microcomputer calculates the difference between the digital value of the output of the A / D converter and the digital value of the output of the A / D converter when the detection coil and the DC amplifier are connected, and the end value is judged based on the calculated value. It is provided with a configuration for making a determination.

Action The present invention, by the above configuration, the digital amount n ₀ of the output of the A / D converter when the switch is placed on the fixed resistor side,
Since the end of the record is determined by the difference (n−n ₀ ) from the digital value n of the output of the A / D converter when the switch is placed on the detection coil side, the offset voltage of the DC amplifier and the temperature of the offset voltage It will not be affected by the drift.

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, 10 is a fixed resistor having the same resistance value as the detection coil 3, 7 is a switch for switching the input connection of the DC amplifier 4 to either the detection coil side or the fixed resistor side by the microcomputer 9, and 8 is a switch. An A / D converter for A / D converting the output of the DC amplifier 4, and 9 is a microcomputer for reading the digital amount of the A / D converter 8 and switching the connection of the switch 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, the switch 7 is switched to the fixed resistor side by the microcomputer 9, and the output voltage of the DC amplifier 4 at that time is stored in the microcomputer 9 as the digital amount n ₀ by the A / D converter 8.
Next, during record performance, switch 7
Is switched to the detection coil side, and 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 8 as a digital amount n into the microcomputer 9. Then, the digital amount n and the digital amount when the switch 3 is switched to the fixed resistor side
determined by the difference between n ₀ (n-n ₀₎ whether came tone arm to the end of the record, for example, if the digital quantity of the speed component of 2 mm / 1 rotation _{n 1, (n-n 0} ) n _{When 1} ,
The tone circuit can be returned by the return circuit 6.

As described above, according to this embodiment, the output of the DC amplifier 4 during the performance of a record is converted into a digital amount by the A / D converter 8, the digital amount is read by the microcomputer 9, and the switch 7 is set on the fixed resistor side. The end of the record is detected by the difference from the digital amount n ₀ when the switch is switched to the end, and the influence of the offset voltage of the DC amplifier 4 and the temperature drift of the offset voltage is removed to detect the end by the speed detection of the tone arm with high accuracy. It can be performed.

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. convert to the amount, reading the digital amount n by a microcomputer, a digital quantity n ₀ when the output of the DC amplifier and converted into a digital value by a / D converter when the switching to the fixed resistor input DC amplifier Of the end of the record by detecting the end of the record by the difference (n−n ₀ ) of the DC amplifier and the influence of the offset voltage of the DC amplifier and the temperature drift of the offset voltage. It can be performed.

[Brief description of drawings]

FIG. 1 is a block diagram of a record end detection device of a swing type tone arm according to an embodiment of the present invention, and FIG. 2 is a block diagram of a record end detection device of a conventional swing type tone arm. 1 ... tone arm body, 2 ... rotor magnet,
3 ... Detection coil, 4 ... DC amplifier, 5 ... Comparator,
6 ... Return circuit, 7 ... Changeover switch, 8 ... A / D
Converter, 9 ... Microcomputer, 10 ... Fixed resistor.

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 the detection coil. A fixed resistor with the same resistance value, a switch that switches the output to the next stage to either the coil side or the fixed resistor side, a DC amplifier that amplifies the output of the switch, and an amplified output of the DC amplifier A / D converter for D / D conversion, a microcomputer that reads the digital amount that is the output of the A / D converter, and a return circuit that returns the tone arm. When a switch is connected to the fixed resistor side, The digital value of the amplified output of the DC amplifier and the digitized output of the DC amplifier when the tone arm is operating when the switch is connected to the coil side. The difference between Le amount, the record of the termination detecting apparatus of a slewing type tone arm, characterized in that the velocity detecting end of the record.