JPH0346898B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION Field of the Invention The present invention relates to a rotation detection device for a tape recorder capable of switching the tape running direction between forward rotation and reverse rotation.

Conventional configurations and their problems In recent years, portable tape recorders have begun to employ mechanisms that allow the tape to travel in both forward and reverse directions during playback and recording.
There are also strict demands for miniaturization, high performance, and cost reduction of such mechanisms.

A conventional rotation detecting device for a tape recorder capable of switching between forward and reverse rotation will be described below. FIG. 1 is a circuit diagram of a conventional rotation detection device, in which 1 is a switching transistor, 2 is a light emitting diode, and 3 is a phototransistor. The light emitting diode 2 is the light emitting side, the phototransistor 3 is the light receiving side, and the first
constitutes an optical sensor. 4 is a switching transistor, 5 is a light emitting diode, and 6 is a phototransistor. The light emitting diode 5 and the phototransistor 6 constitute a second optical sensor. The first optical sensor detects the rotation of the take-up reel during normal rotation,
The second optical sensor is fixed in the vicinity of reflection plates 7 and 8, which are respectively linked to the reel stand, so as to detect the rotation of the take-up reel at the time of reverse rotation. The reflecting plates 7 and 8 function to turn on and off the light input to the phototransistors 3 and 6.

Regarding the rotation detection device configured as above,
The operation will be explained below. First, when the tape rotates forward,
A positive signal is input to the base of the switching transistor 1, the transistor 1 is turned on, the light emitting diode 2 lights up, the reflection plate 7 is rotated, the phototransistor 3 is turned on and off, and an output pulse is generated. At this time, a negative signal is applied to the base of the switching transistor 4 to turn it off. Therefore, the second optical sensor does not operate.

On the contrary, when inverting, a negative signal is applied to the base of the switching transistor 1 so that the first photosensor does not operate, a positive signal is applied to the base of the switching transistor 4 to make the light emitting diode 5 glow, and the reflection plate 8 is turned on. The phototransistor 6 is turned on and off by rotation, and the output of the second optical sensor is obtained. As a result, the first and second optical sensors are switched to detect the rotation of the take-up reel during rotation in the forward and reverse directions.

However, in the above conventional configuration, the switching transistor 1 is used as the switching signal of the optical sensor.
Since it is necessary to give different signals (positive and negative inverted) to each base of 4 and 4, there are two types of switching signals, and the signal processing circuit becomes complicated.
Additionally, there was a problem in that the number of parts increased.

Purpose of the invention The present invention solves the above-mentioned conventional problems.
It is an object of the present invention to provide a rotation detection device for a tape recorder that can switch between normal and reverse optical sensors with a simple configuration and reduce costs.

Structure of the Invention The present invention operates by switching between an optical sensor that detects the rotation of the take-up reel during normal rotation and an optical sensor that detects the rotation of the take-up reel during reverse rotation, so that one optical sensor emits light. Connect a diode in series with the diode and ground it, connect a transistor in series with the light emitting diode of the other light sensor and ground it,
By connecting these two light emitting diodes to a common power source, the light emitting state of the two light emitting diodes can be changed by turning on and off one transistor, and one light sensor is activated while the other light sensor is inactivated. It is characterized by the fact that
According to this configuration, it is possible to switch the rotation detection of the reel stand between normal rotation and reverse rotation to the winding side with one switching signal, and has the advantage that accurate tape running detection can be realized.

DESCRIPTION OF THE EMBODIMENTS FIG. 2 shows a rotation detecting device for a tape recorder that switches between forward and reverse rotation in an embodiment of the present invention. In FIG. 2, 9 is a diode, 2 is a light emitting diode, 3 is a phototransistor, 4 is a transistor, 5 is a light emitting diode, and 6 is a phototransistor. Each pair of transistors 6 constitutes an optical sensor for detecting the normal rotation side and the reverse rotation side. These optical sensors are fixed in the vicinity of reflection plates 7 and 8 that are linked to the reel stand and have the function of turning on and off the light input from the light emitting diode to the phototransistor.

The operation of the rotation detection device of this embodiment configured as described above will be described below.

First, a negative signal is applied to the base of the normal rotation transistor 4 (it may be open) to turn it off.
Therefore, no current flows through the light emitting diode 5, and the optical sensor on the reverse side does not operate. At this time, a current flows through the light emitting diode 2 via the diode 9, and the phototransistor 3 is turned on and off by the reflection plate 7 which is interlocked with the take-up reel during normal rotation, and a rotation detection pulse is output.

During reflection, a positive signal is applied to the base of the transistor 4 to saturate the collector-emitter voltage VCE. Then, the transistor 4 becomes conductive, the light-emitting diode 5 lights up, and the phototransistor 6 is turned on and off by the reflection plate 8, which is interlocked with the take-up reel at the time of reversal, and a pulse for rotation detection is output.
If the forward voltages V ₂ and V _{4 of the light emitting diodes 2 and 5} are equal, and the forward voltage V ₉ of the diode 9 is larger than the collector-emitter saturation voltage V _CE of the transistor 4, the potential V at point A in FIG. _A is V _A = V ₂ +
V _CE and V _A <V ₁ +V ₂ , so that sufficient current does not flow through the light emitting diode 2 . Therefore, since the phototransistor 3 cannot be turned on, the optical sensor on the normal rotation side does not operate. diode 9
When a silicon diode is used as the transistor, the forward voltage _V1 is generally about 0.6V, and the collector-emitter saturation voltage of some transistors is about 0.1 to 0.2V, so the above setting conditions can be easily achieved.

In this way, two photosensors can be easily switched by a control signal to one switching transistor.

Effects of the Invention The present invention comprises two sets of optical sensors consisting of a light emitting diode and a phototransistor, the diode being connected in series to the light emitting diode constituting one optical sensor and the light emitting diode constituting the other optical sensor being connected in series. Since the connected transistors are connected to a common power source, the light emitting states of the two light emitting diodes can be changed only by a control signal to these transistors. As a result, the operations of the two optical sensors are easily switched, and the rotation of the take-up reel is detected. Therefore, since switching is possible with a single control signal, the pre-stage control circuit for rotation detection can be easily configured, and the switching circuit can also be configured with a minimum number of parts, reducing the number of parts and downsizing the device. It has advantages such as:

[Brief explanation of drawings]

FIG. 1 is a circuit diagram of a conventional rotation detection device, and FIG. 2 is a circuit diagram of a rotation detection device according to an embodiment of the present invention. 2... Light emitting diode, 3... Phototransistor, 4... Switching transistor, 5... Light emitting diode, 6... Phototransistor, 7,8
...Reflector, 9...Diode.

Claims (1)

[Claims] 1. A tape recorder capable of switching the running direction of the tape between a forward rotation direction and a reverse rotation direction is configured such that rotation detection of a take-up reel is performed by independent optical sensors during forward rotation and during reverse rotation, and a first A diode is connected in series to the light emitting diode of the second sensor and grounded, a transistor is connected in series to the light emitting diode of the second sensor and grounded, and the light emitting diodes of the first and second sensors are connected to a common power source. A rotation detection device characterized in that the light emitting state of the light emitting diode is changed by connecting the transistor to the transistor and turning it on and off according to the direction of rotation, thereby switching between the first and second sensors.