JPS61180586A - Rotating direction detector for rotary article - Google Patents

Abstract

PURPOSE:To reduce the size of a detector by providing difference between rising and falling times of an FG signal, and detecting a tape feeding direction by the differentiated value of this signal. CONSTITUTION:Holes are formed at a rotary plate 1, and a detector formed of a light source 2 and a photoreceptor 3 detects the hole to output a signal (a) or a'. The signal (a) or a' is differentiated, and converted to signals (b), b'. When the plate 1 is rotated in the prescribed direction, a detection signal (a) is output, and the value of the signal (b) is, in this case, the set value or lower. When the plate 1 is reversely rotated, the detection signal a' is output. At this time the value of the signal b' becomes the set value or higher, and a reverse signal c' is output.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Application of the Invention] The present invention relates to a mode in which the tape running of a VTR is reversed, and relates to a method and a circuit for detecting that the direction of tape running is reversed.

[Background of the invention]

As a conventional example, there is an example described in the above-mentioned literature. In this example, a light source and two phototransistors are used to detect the rotation direction based on the phase difference between the phototransistors. In this case, it is necessary to use two expensive phototransistors, and it is not suitable for applications such as VTRs, where power saving and small size are required.

[Purpose of the invention]

SUMMARY OF THE INVENTION An object of the present invention is to provide a system that shortens the tape transition time of a VTR by modifying the conventionally used F'G signal and using it as a detection signal when tape running is reversed.

[Summary of the invention]

In the present invention, the conventionally used signal is transformed by FG times,
A difference is provided between the rise time and the fall time, and the tape running direction is detected using this signal using a differentiation circuit and a comparison circuit.

[Embodiments of the invention]

FIG. 1 shows a frequency generator that constitutes a main part of a specific embodiment of the present invention, FIG. 2 shows a peripheral circuit, and FIG. S shows waveforms of each part thereof. Hereinafter, FIGS. 1 to 3 will be explained.

In Figures 1 to 3, 1 is a rotary plate having an opening as shown in the disk, 2 is a light source facing the opening of rotation &1, and 5 is a rotating plate through a slit 4. Light receiving part of light source 2, '5.5' is amplifier, 6 is differentiation circuit, 7 is comparison degree
It is a vessel.

In addition, (a), (b), and (C) are the output waveforms of each part,
(a'), (t)'), and (C') are waveforms of each part when the rotation direction changes.

Light passing through the rotary plate 1 from the light source 2 is guided to the light receiving section 3 via the slit 4. A photodiode is often used for the light receiving section 3. The light incident on this light receiving section 3 is
It is converted into voltage using a photodiode, etc. This converted voltage is amplified by an amplifier 5. As a result, waveform (a) K
The waveform shown is obtained.

On the other hand, the output of this amplifier 5 is input to a differentiating circuit 6,
The output waveform (b) of this differentiating circuit 6 is obtained. This output is then input to a comparator 7.

The other input of the comparator 7 is set to a constant comparison level by a resistor, and this comparison level is compared with the waveform (b). In the rising portion of waveform (a), the output voltage amplitude of the differentiating circuit is small. Therefore, if the comparison level of the comparator 7 is set above this voltage, the output of the comparator 7 will always be 1L level.

On the other hand, when the rotating direction of the rotating plate 10 is reversed, the output waveform (a') of the amplifier 5 is obtained. When this waveform <1) is passed through a differentiating circuit, a waveform (b') is obtained. If the comparison level of the comparator 7 is set between the waveforms (b) and (b'), the output waveform of the comparator 7 will have the following as shown in (C'):
A pulse-like output waveform can be obtained. As a result, the rotation direction can be easily detected by distinguishing between the waveforms (C) and (C'). Further, although the explanation has been given using a rotating plate as a specific example, the present invention can easily be applied to cases where the rotating direction is detected using a reflective sensor or a capacitive sensor.

Although not described further, the outputs of the amplifiers 5 and 5' can be used as a frequency generator for rotation control.

〔Effect of the invention〕

As a result of the present invention, a detection circuit that conventionally used two photodiodes to detect the rotation direction can be replaced with one photodiode, and the detection device can also be made smaller.

[Brief explanation of drawings]

FIG. 1 is an explanatory diagram of a rotating disk and a detection device according to an embodiment of the present invention, FIG. 2 is a peripheral circuit diagram, and FIG. 3 is a waveform diagram of each part. 1...Rotating disk, 5...Light receiving section, 6...Differentiating circuit, 7...Comparator. O 1 Illustration 2 Close

Claims (1)

[Claims] 1. In a frequency generator having a frequency generator interlocked with a rotating object and using the frequency generator as a speed reference signal of a motor that controls the rotating object, if the rising differential speed and falling differential speed of the detected frequency are different. A circuit for detecting the rotational direction of a rotating object.