JPH026505Y2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a tape end detection circuit for electrically detecting the end of a tape in a magnetic recording/reproducing device and returning the device to a stopped state.

Generally, magnetic recording and playback devices use a tape end detection circuit that electrically detects when the rotation of the reel shaft stops at the end of the tape and activates the plunger, which locks the magnetic recording and playback device. The device is configured to return to the stopped state at the end of the tape by releasing the plunger at the end of the tape.

If such a tape end detection circuit is used in a magnetic recording/playback device that uses a battery as a power source, if the battery voltage drops, sufficient drive current will not flow to the plunger at the end of the tape, and the plunger will not operate. However, the locking mechanism is not released even when the plunger is turned off, resulting in malfunctions, and not only is the plunger unable to return to its stopped state, but current continues to flow through the plunger, resulting in significant wasteful power consumption.

Therefore, the present invention was developed to solve this problem.If the plunger cannot release the locking mechanism at once due to a drop in power supply voltage, the plunger is driven intermittently to ensure that the locking mechanism is released. The purpose of the present invention is to provide a tape end detection circuit that can return the tape to a stopped state.

Embodiments of the present invention will be described below with reference to the drawings. 1
is a Hall IC that generates a pulse output according to the rotation of the ring magnet 2 which is rotated in conjunction with the rotation of the reel shaft, and generates a pulse output from the terminal C while the tape is running and the reel shaft is rotating. 3 is a charging/discharging circuit that rectifies the pulse output from Hall IC 1 and charges/discharges capacitor C _2. The potential at point A is maintained at H level while the reel shaft is rotating, and when the reel shaft stops rotating, the potential at point A is maintained at H level. When the pulse output from IC1 disappears, it changes to L level. That is, the charging/discharging circuit 3 is a detection circuit that detects the stoppage of rotation of the reel shaft. 4 is a Schmitt circuit for the purpose of waveform shaping controlled by the potential at point A of the charging/discharging circuit 3. 5 is Schmitt circuit 4
This is a plunger drive circuit which is controlled by switching by the output of , and is configured to drive the plunger 6 by turning on transistor Q ₅ when the rotation of the reel shaft stops at the end of the tape. 7 is a power supply voltage detection circuit, when the power supply voltage drops to a predetermined voltage,
By supplying an H level signal to the Schmitt circuit 4 and forcibly inverting the Schmitt circuit 4, the plunger 6 is temporarily rendered inoperable.

Next, the operation of the present invention having such a configuration will be explained.

First, when the power supply voltage is high enough and the tape is running, a pulse output is generated from the Hall IC 1 due to the rotation of the ring magnet 2 as the reel shaft rotates, and the capacitor C ₂ is repeatedly charged and discharged.
The potential at the point is maintained at H level, and in the Schmitt circuit 4, transistor Q ₂ is kept conductive and transistor Q ₃ is kept non-conductive. Therefore, in the plunger drive circuit 5, the transistor _Q4 is set to be conductive and the transistor _Q5 is set to be non-conductive, so that the plunger 6 is not driven. On the other hand, in the power supply voltage detection circuit 7, the transistor _Q6 is turned on by the base voltage set by the resistors _R1 and _R2 , and the collector of the transistor _Q6 is maintained at L level.

When the end of the tape is reached in such a state, the ring magnet 2 stops rotating as the reel shaft stops rotating, and the Hall IC 1 no longer generates a pulse output, so the capacitor C ₂ of the charging/discharging circuit 3 is no longer charged. Since the discharge is performed without being performed, the potential at point A is changed to L level. Therefore, the Schmitt circuit 4 is inverted and the transistor _Q3 is made conductive, so that the transistor _Q4 of the plunger drive circuit 5 is made non-conductive and the transistor _Q5 is made conductive. In this way, the plunger 6 is driven to release the locking mechanism that is held in the regenerated state, etc., and return to the stopped state.

In this case, since the power supply voltage is sufficiently high, the plunger 6 operates reliably and the locking mechanism can be reliably released with one operation.

Next, when the power supply voltage drops, the operation is the same as described above while the tape is running, but even if the tape reaches the end and the plunger 6 is operated in the same way as described above,
When the power supply voltage decreases, the plunger 6 does not operate sufficiently, causing a malfunction in which the locking mechanism is not released. However, in the present invention, the plunger 6 is driven intermittently by the function of the power supply voltage detection circuit 7.

That is, when the plunger 6 is first operated at the end of the tape, as the power supply voltage is further reduced, the transistor Q ₆ whose base bias is set by the resistors R ₁ and R ₂ is activated until the power supply voltage drops to a predetermined voltage. Then, it is inverted to non-conducting, and by supplying an H level signal from the collector to the Schmitt circuit 4,
As the Schmitt circuit 4 is reversed, the transistor Q5 of the plunger drive circuit ₅ becomes non-conductive and the current to the plunger 6 is cut off. When the supply voltage is restored by interrupting the current to the plunger 6, the Schmitt circuit 4 is activated by conduction of the transistor _Q6 .
The plunger 6 is driven again by being reversed again. In this way, the plunger 6 is driven intermittently until the locking mechanism is released and the power switch 8 is turned off.

As described above, the tape end detection circuit of the present invention intermittently drives the plunger that releases the locking mechanism at the end of the tape when the power supply voltage drops to a predetermined voltage. Even if the locking mechanism cannot be released by the locking mechanism, the locking mechanism can be reliably released, and it has an extremely practical effect especially when applied to a magnetic recording/playback device that uses a battery as a power source.

[Brief explanation of the drawing]

The drawing is a diagram showing the configuration of a tape end detection circuit according to the present invention. 1... Hall IC, 3... Charge/discharge circuit, 4...
Schmitt circuit, 5...plunger drive circuit,
6... Plunger, 7... Power supply voltage detection circuit,
8...Power switch.

Claims (1)

[Claims for Utility Model Registration] A plunger that releases the locking mechanism of a magnetic recording/playback device and returns it to a stopped state, and a reel at the end of the tape based on the presence or absence of a pulse output that is generated in conjunction with the rotation of the reel shaft. a detection circuit that detects rotation stoppage of the shaft; a power supply voltage detection circuit that detects whether the power supply voltage is equal to or higher than a predetermined voltage; output signals of the detection circuit and the power supply voltage detection circuit are input, and output signals from the power supply voltage detection circuit are inputted; When a signal indicating that the power supply voltage is higher than a predetermined voltage is output, the power supply to the plunger is controlled based on the output signal from the detection circuit, and the power supply voltage is determined from the power supply voltage detection circuit to be lower than the predetermined voltage. A tape end detection circuit comprising: a drive circuit that cuts off power supply to the plunger regardless of the output signal of the detection circuit when a signal indicating that the detection circuit is low is output.