JPH03250444A - Tape end detecting circuit for magnetic recording and reproducing device - Google Patents

Abstract

PURPOSE:To prevent a built-in battery from being abnormally consumed by deciding the start and final ends of a magnetic tape based upon an output voltage corresponding to the rotational frequency of feeding and winding reels and lighting up a light emitting element. CONSTITUTION:When the rotational frequency of the feeding reel is increased in the vicinity of the final end of a video tape and a reel pulse SP2 with a high frequency band is outputted, the pulse SP2 is shaped at its waveform, the shaped signal is applied to a frequency conversion circuit 14 and a DC voltage corresponding to the frequency is outputted to the non-inversional input terminal of a comparator 16. When the DC voltage exceeds 3V, 5V voltage is outputted from the comparator 16 and impressed to the base of an output transistor(TR) Q4 through a diode D4. Thereby, the TR Q4 is turned on and a power supply voltage is impressed to an LED D1 to turn on the LED D1. Since the LED D1 is turned on only when the tape exists in the vicinity of the start or end terminal of the tape, power consumption is sharply reduced and the consumption of the built-in battery is suppressed.

Description

Detailed Description of the Invention (Field of Industrial Application) The present invention relates to a magnetic recording and reproducing device such as a video tape recorder and an audio tape recorder, and more particularly to a magnetic recording and reproducing device that detects the beginning and end of a magnetic tape. The present invention relates to a tape end detection circuit for an apparatus.

(Prior Art) In a magnetic recording/reproducing device such as a video tape recorder, the operation of each part of the device is stopped when the running video tape reaches the start or end position during playback mode or recording mode. In order to perform an automatic rewind operation or an automatic fast forward operation, a tape end detection circuit is provided to detect the start and end positions of the videotape.

As shown in FIG.
etc. When the video cassette A is loaded into the main body V of the video tape recorder, the light emitting section 3, the winding side light receiving section 4, and the supply side light receiving section 5 are arranged so as to face each other with the video tape B in between. There is.

The signal generator 2 outputs a pulse signal, and when a DC voltage is applied, it provides a pulse signal with a constant period to the light emitting section 3. This light emitting section 3 includes a transistor Q and a light emitting diode D.

The base of the transistor Q1 is the base resistor R.
, to the output of the signal generator 2.

In addition, the collector of transistor Q is connected to the power supply voltage (+1
2 V), the emitters of which are connected via a protective resistor R1 to the anodes of light-emitting diodes D, respectively, and the cathodes of light-emitting diodes D, which are connected to ground.

Then, the pulse signal from the signal generator 2 is transmitted to the transistor Q.
, the light emitting diode D1 emits light in response to the current amplified by the transistor Q.

The winding-side light-receiving section 4 for detecting the tape start end and the supply-side light-receiving section 5 for detecting the tape end have the same circuit configuration.
Each of them is equipped with a phototransistor Q2. This phototransistor Q2 is arranged toward the light emitting diode DI side, and has an emitter connected to ground and a collector connected to a power supply voltage (+5 V) via a resistor R1.

Thereby, when the phototransistor Q2 receives irradiated light from the light emitting diode D, the collector output is sent to the microcomputer of the control section.

Note that the light emitting diode DI is arranged approximately at the center of the video cassette A when the video cassette A is loaded into the main body V of the video tape recorder. In this video cassette A, a video tape B is wound around a take-up reel AI and a supply reel A2, and transparent or milky white leader tape sections are provided at both ends of the video tape B. It has a structure that allows light to pass through. Moreover, as shown in FIG.
The phototransistor Q2 of the supply side light receiving section 5 is arranged on the left side of the cassette housing section 1, and the light emitting diode D1 and the two phototransistors Qz
, Q2 are arranged on the same line with the video tape B in between. As a result, the light from the light emitting diode D can be irradiated to the vicinity of the supply reel A2, the take-up reel A, and the nearby videotape B. Therefore, depending on whether the irradiated light passes through the videotape B or not, the videotape B It is possible to detect the start and end of the .

Next, the operation of the tape end detection circuit 1 having the above configuration will be explained.

First, when putting the video tape recorder V into playback mode or recording mode, when the corresponding mode switch (not shown) is turned on, a pulse signal with a voltage level as shown in Figure 4 fa) is output from the signal generator 2. be done. When this pulse signal is applied to the transistor Q, a current amplified output signal is supplied to the light emitting diode D1. This light emitting diode D1 emits light at a level shown in the figure) in response to the output signal. This light is irradiated towards videotape B;
If it is not the beginning or the end, the irradiated light is blocked by the videotape B. Therefore, the winding side light receiving section 4
The phototransistor Q2 of the light receiving section 5 on the supply side is both in the F state, and, for example, the power supply voltage +5■ is applied as a detection signal S■1 to a microcomputer (not shown). When the microcomputer receives the detection signal S, it determines that the video tape B is in the middle, and maintains the current mode. For example, if videotape B is running, tape running continues.

After this, videotape B continues to run, and videotape B
At the start or end of , the irradiated light from the light emitting diode D passes through the leader tape section on the supply reel A2 side or the take-up reel A side, and any phototransistor Qz
The light is received by.

Then, a pulse signal having a waveform shown in FIG. 4(C) is output from the collector of the phototransistor Q2 as a detection signal SV,
is output as When this detection signal SV is applied to the microcomputer, the microcomputer determines that the videotape B has reached the beginning or end, and outputs a control signal to stop each part of the device. This causes the video tape recorder to be placed in the stop mode, or to be placed in the stop mode after rewinding the video tape B.

(Problem to be Solved by the Invention) By the way, the conventional tape end detection circuit 1 described above is designed to keep the light emitting diode DI lit at all times, but the light emitting diode D1 normally consumes a current of 20 to 50 mA. This power consumption may not be negligible depending on the situation.

For example, a portable video tape recorder for outdoor use uses a built-in battery as its power source, so if the light emitting diode D+ continues to light up while video tape B is running, there is a considerable power loss, and the operating time of the video tape recorder is This was one of the factors that shortened the period.

The present invention has been made in view of the above circumstances, and its purpose is to efficiently light up light emitting elements for detecting the start and end ends of a magnetic tape, suppress power loss, and prevent battery power consumption. The purpose of the present invention is to provide a recording/playback device.

(Means for Solving the Problems) In order to solve the above problems, the magnetic recording/reproducing apparatus of the present invention has a light emitting section having a light emitting element and a light receiving section having a light receiving element when a magnetic tape is loaded into the main body of the apparatus. are arranged to face each other with the magnetic tape interposed therebetween, and the light from the light emitting element is transmitted through transparent portions formed at the starting and ending ends of the magnetic tape and is received by the light receiving element.
In a tape end detection circuit of a magnetic recording/reproducing device configured to detect the start end and end end of a magnetic tape and stop the running of the magnetic tape, the rotation of each of a supply reel and a take-up reel that winds the magnetic tape is performed. A rotation detecting means outputs a voltage according to the number of rotation detecting means, each output voltage from this rotation detecting means is compared with each comparison reference level set in advance corresponding to each, and each output voltage corresponds to each a comparison means for detecting that winding of the magnetic tape on the supply reel or take-up reel is near the start end or near the end when the comparison reference level is exceeded, and outputs a detection signal; A configuration including a driving means for driving the light emitting element to turn on based on a detection signal is adopted.

(Function) In the above configuration, when the magnetic tape is run, a voltage is output according to the rotational speed of each of the supply reel and the take-up reel around which the magnetic tape is wound.

Each output voltage is applied to a correspondingly provided comparison means. In the comparing means, when each of the derived output voltages is below each comparison reference level set in advance corresponding to each one, the magnetic tape is neither at the starting end nor at the ending end, so no detection signal is output, and therefore the drive is stopped. Since the means are not driven, the light emitting element does not light up.

On the other hand, when each output voltage exceeds each comparison reference level, since the magnetic tape has reached the vicinity of the start end or the vicinity of the end, the comparison means outputs a detection signal to the drive means. The driving means is driven by this detection signal to light up the light emitting diode. After that, when the light emitted from the light emitting diode passes through the transparent part formed on the starting end side of the magnetic tape and is received by the light receiving element, it is detected that the magnetic tape has been wound up to the starting end on the supply reel A2. .

On the other hand, when the irradiated light passes through the transparent portion formed at the end of the magnetic tape and is received by the light receiving element, it is detected that the magnetic tape has been wound up to the end on the take-up reel AI.

In this way, since the light emitting diode lights up when the magnetic tape comes near the starting end or near the ending end, the lighting time can be shortened.

(Example) Hereinafter, one embodiment of the present invention will be described with reference to the drawings.

FIG. 1 is a block diagram showing the electrical configuration of a magnetic recording/reproducing device.

This magnetic recording and reproducing apparatus includes a conventional tape end detection circuit 1 shown in FIG. The video tape recorder is configured to include a first comparator 15, a second comparator 16, etc., and the operation of each part of the video tape recorder is controlled by a control section consisting of a microcomputer. Note that the same parts as in the conventional example shown in FIG. 2 are denoted by the same reference numerals, and redundant explanation will be omitted.

The take-up side rotation detection circuit 6 outputs a voltage according to the rotation speed of the take-up reel AI (see FIG. 3) on which the video tape B is wound. , a waveform shaping circuit 13, a frequency conversion circuit 14, and the like. The rotating reflector 12 forms a continuous light and dark pattern (the white part is indicated by 11a and the component part is indicated by llb) painted in two colors such as black and white radially from the center toward the outer periphery, and is not shown. It is attached to the surface of the take-up reel A, which is linked to the rotation of the capstan motor. Further, the photo ink converter 12 includes a light emitting diode D2 and a phototransistor Q, and is arranged facing the rotating reflecting plate 12.

The anode of the light emitting diode D2 is connected to the power supply voltage via the resistor R4, and the cathode is connected to the ground.

Also, the emitter of phototransistor Q3 is connected to ground,
The collector is connected to the power supply voltage (+5 V) via a resistor R3. As a result, when the light from the light emitting diode D2 is irradiated onto the rotating reflection plate 12 and the reflected light is received by the phototransistor Q3, a reel pulse SP is outputted in proportion to the number of rotations of the take-up reel A. is supplied from the collector via the waveform shaping circuit 13 to a microcomputer and a frequency conversion circuit 14 (not shown). The microcomputer receives the reel pulse SPI, detects abnormal rotation of the take-up reel A, and controls the operation of the device. Further, the frequency conversion circuit 14 operates in response to the rHJ level signal voltage SVS output when the capstan motor is reversed, and supplies a DC voltage corresponding to the frequency of the reel pulse SPI to the non-inverting input terminal of the first comparator 15. It is designed to output to . This first comparator 15 compares the DC voltage with a reference voltage, and has a resistor R6 connected to the power supply voltage (+5 V) at one end at its inverting input terminal.
A voltage divided by a resistor R1 and a resistor R11 each having one end connected to the other end of the resistor R6 is introduced as a reference voltage.

The resistance values of the resistors R1 and R8 are set in advance, and the resistor R1 is connected to the ground via the constant speed running switch S1, and the resistor R8 is connected to the ground via the high speed running switch St. Then, when the constant speed running switch S1 is turned on, a reference voltage corresponding to the recording mode and the playback mode is output to the first comparator 15, and when the high speed running switch S2 is turned on, it is compatible with the rewind mode and the fast forward mode. The reference voltage thus obtained is output to the first comparator 15. And this first comparator 15
The output of is connected to the base of output transistor Q4 via diode D3 and base resistor R1. This output transistor Q4, resistor R3, and diode Dx
(Da, D,) constitute a drive circuit 8.

The output transistor Q4 operates the tape end detection circuit 1, and has an emitter connected to ground and a collector connected to the light emitting diode D of the light emitting circuit section 3. As a result, the reel pulse SP1 outputted as the winding reel A1 rotates is frequency-converted by the frequency conversion circuit 14, and then converted into a DC voltage by the first comparator 15.
When a voltage is applied to the output transistor Q4 and is compared with a reference voltage and outputted, the tape end detection circuit 1 is activated.

Note that this tape end detection circuit 1 has the same configuration as the conventional example shown in FIG.

Further, the supply side rotation detection circuit 7 has a basic configuration similar to that of the winding side rotation detection circuit 6, and the rotation reflection plate 11 has the following configuration:
It is attached to the surface of the supply reel A2 shown in FIG. Then, the reel pulse SP2 that is output as the supply reel A2 rotates is waveform-shaped by the waveform shaping circuit 13, and then receives the rHJ level signal voltage SV that is output when the capstan motor rotates normally. It is adapted to be applied to the frequency conversion circuit 14 for operation. A DC voltage corresponding to the number of rotations of the supply reel A2 is applied from the frequency conversion circuit 14 to the non-inverting input terminal of the second comparator 16, and the voltage that is compared with the reference voltage and output is outputted from the quadrature transistor.

The tape end detection circuit 1 is configured to operate when the tape end detection circuit 1 is supplied. Further, the reference voltage applied to the inverting input terminal of the second comparator A2 is the same as the reference voltage applied to the inverting input terminal of the first comparator A1, and the reference voltage applied to the inverting input terminal of the second comparator A2 is the same as the reference voltage applied to the inverting input terminal of the first comparator A1. A voltage divided by R6 and a resistor R9 and a resistor R each having one end connected to the other end of the resistor R6 is introduced as a reference voltage. The resistance values of the resistors R-I and R8 are set in advance, and the resistor R7 is connected to the ground via the constant speed running switch S3, and the resistor R11 is connected to the high speed running switch S4.
It is configured to be connected to ground via. The output of this second comparator 16 is then connected to the diode D4.
and is connected to the base of the output transistor Q4 via the base resistor R1.

Reference numeral 9 denotes a control signal generator, which is activated by a control signal from the microcomputer output when the video tape B starts running, and supplies a signal voltage of "H" level to the differentiating circuit 10. This differential circuit 10
consists of a capacitor C0 and a resistor R, 3, and uses the signal voltage as a trigger to output a drive signal for a certain period of time only at the start of running to the video tape, and lights up the light emitting diode D for the required period of time. By providing the control signal generator 9 and the differentiation circuit 10, for example, the video tape B can be input from a place other than the leader tape section.
The presence or absence of videotape B can be determined when the vehicle is running.

Next, the operation of the tape end detection circuit having the above configuration will be explained.

When the operator selects the recording mode or the playback mode when using the video tape recorder, the supply reel A2
Turn on the constant speed running switch S3 on the side. After that, when the recording mode or playback mode is selected, a control signal is sent from the microcomputer to each part of the device, and based on this control signal, the capstan motor is driven in forward rotation, the supply side rotation detection circuit 7 is activated, and the video Tape B starts running.

At this time, near the end of videotape B, the number of tape windings on the supply reel A2 side is smaller than on the take-up reel A1 side, so the rotation speed of the supply reel A2 becomes faster and a high frequency reel pulse SP2 is output. Ru. and,
When this reel pulse sP2 is waveform-shaped and then applied to the frequency conversion circuit 14, a DC voltage corresponding to this frequency is outputted and applied to the non-inverting input terminal of the second comparator 16. At this time, when the DC voltage exceeds 3cm, a voltage of 5V is output from the second comparator 16, and is applied to the base of the output transistor Q4 via the diode D4. As a result, the output transistor Q4 is turned on, supplying the power supply voltage (+12V) to the light emitting diode D1, and the light emitting diode D is turned on.

Thereafter, the videotape B continues to run and is wound up in turn toward the winding loop A, and when it reaches the leader tape section, which is the end of the videotape B, the light from the light emitting diode D1 is transmitted to the phototransistor roller 2. A detection signal S2 of a power supply voltage (+5 V) indicating that the end of the tape has been detected is applied to a microcomputer (not shown). As a result, the microcomputer determines that the video tape B has reached its end, and sends a control signal to each part of the device to stop the drive. When the capstan motor is stopped by this control signal, the reel pulse SP
Since the generation of , also stops, the output of the frequency conversion circuit 14 becomes OV. Therefore, the output of the second comparator 16 is also 0.
■ Therefore, the output transistor Q4 turns OFF,
The light emitting diode D1 is also turned off.

Incidentally, when the operator selects the fast-forward mode, it is sufficient to turn on the high-speed running switch S4 on the supply reel A2 side, and the subsequent operation is exactly the same as described above.

Further, when the capstan motor is started, a trigger signal outputted from the control signal generator 9 causes the differentiating circuit 10 to output a drive signal for a certain period of time. Therefore, the light emitting diode D1 remains lit for a required period of time after the start of operation, and then turns off.

Next, after the end of the videotape B is detected, if the operator selects the rewind mode, the winding loop A1
Turn on the high speed running switch S2 on the side. After that, when the rewind mode is set, a control signal is sent from the microcomputer to each part of the device, and based on this control signal, the capstan motor is driven in reverse, the winding side rotation detection circuit 6 is activated, and the video tape B starts running. On this occasion,
In the vicinity of the beginning of videotape B, winding rule A is used.

Since the number of tape windings on the side of the supply reel A2 is smaller than on the side of the supply reel A2, the number of rotations of the take-up reel A1 becomes faster, and a high frequency reel pulse S P + is output.

When this reel pulse S P + is waveform-shaped and then applied to the frequency conversion circuit 14 , a DC voltage corresponding to this frequency is outputted and applied to the non-inverting input terminal of the first comparator 15 . At this time, a DC voltage of 4■ or more is applied to the non-inverting input terminal of the first comparator 15 depending on the frequency, but since the reference bias voltage applied to the inverting input terminal is approximately 4■ , the first comparator 15 outputs a voltage of 5V. As a result, the output transistor Q4 is turned on and the light emitting diode D1 is lit.

Thereafter, the videotape B continues to run and is wound up sequentially onto the supply reel A2, and when it reaches the leader tape section, which is the starting end of the videotape B, the light from the light emitting diode D+ is received by the phototransistor 0□. , a detection signal SV of a power supply voltage (+5 V) indicating that the beginning of the tape has been detected is applied to a microcomputer (not shown). In addition, the microcomputer determines that the video tape B has reached the starting end, and sends a control signal to each part of the device to stop the drive. When the capstan motor is stopped by this control signal, the reel pulse S
Since the generation of P also stops, the output of the frequency conversion circuit 14 becomes O■. Therefore, the output of the first comparator 15 is also 0, so the output transistor Q4 is activated.
The light emitting diode D is also turned off.

As explained above, 1. The tape end detection circuit of the present invention has the following features:
When videotape B is run in various modes such as recording/playback/fast forwarding, rewinding, etc., the light emitting diode D1 is activated only when videotape B is near the beginning or end.
Since the light emitting diode DI is configured to light up, it is possible to prevent a large power loss as would occur when the light emitting diode DI is kept on all the time.

(Effects of the Invention) The tape end detection circuit of the magnetic recording and reproducing apparatus according to the present invention detects the starting end and ending end of the magnetic tape based on the output voltage according to the rotational speed of the supply reel and the take-up reel on which the magnetic tape is mounted. The light-emitting element is configured to light up only when the magnetic tape is near the start and end of the magnetic tape, compared to the case where the light-emitting element is kept on all the time and the start and end of the magnetic tape are exposed. , power consumption can be significantly reduced. This has the effect of preventing the built-in battery from being exhausted, for example, in a portable video tape recorder or audio tape recorder that has a built-in battery.

[Brief explanation of drawings]

FIG. 1 is a block diagram showing the electrical configuration of a tape end detection circuit of a magnetic recording/reproducing apparatus according to the present invention, FIGS. 2 to 4 show a conventional example, and FIG. 2 is a tape end detection circuit. FIG. 3 is a schematic diagram of the configuration of a video tape recorder containing a video cassette, and FIG. 4 is an operational waveform diagram of each part of the circuit. 1... Tape end detection circuit 4゜1 3... Light emitting circuit section 5... Light receiving circuit section 6... Winding side rotation detection circuit 7... Supply side rotation detection circuit 8... Drive circuit 5...First comparator 6...Second comparator

Claims (1)

[Scope of Claims] 1) When a magnetic tape is loaded into an apparatus main body, a light emitting section having a light emitting element and a light receiving section having a light receiving element are arranged to face each other with the magnetic tape interposed therebetween, and the light emitting element The light from the magnetic tape is transmitted through transparent portions formed at the start and end ends of the magnetic tape and received by the light receiving element, whereby the start and end ends of the magnetic tape are detected and the running of the magnetic tape is stopped. In the tape end detection circuit of the magnetic recording and reproducing apparatus configured, a rotation detection means outputs a voltage corresponding to the rotation speed of each of the supply reel and the take-up reel around which the magnetic tape is wound; Each output voltage is compared with each preset comparison reference level, and when each output voltage exceeds each corresponding comparison reference level, the magnetic tape is transferred to the supply reel or take-up reel. Comparing means for detecting that the winding is near the start end or near the end and outputting a detection signal; and a driving means for driving the light emitting element to turn on based on the detection signal from the comparing means. Features: Tape edge detection circuit for magnetic recording and reproducing devices.