JPS5847545Y2 - Tape stop detection circuit - Google Patents

Description

[Detailed Description of the Invention] The present invention relates to a tape end detection circuit for a tape recorder, and more specifically, this circuit uses a switch that repeatedly turns on and off while the tape is running in conjunction with the tape feeding mechanism. During this ON/OFF repeated signal output, the charging and discharging of the capacitor is regulated so that the voltage does not reach a certain level, and the oscillation that has a predetermined threshold level and oscillates when the externally applied voltage reaches the threshold level. The charging potential of the capacitor is applied to the circuit as an external voltage, and when the tape end is reached and the capacitor's charging voltage exceeds the threshold level, an oscillation pulse is output.The present invention accurately detects the tape end. At the time of detection, a pulse of a predetermined width is output, and this pulse can be used to automatically reverse the tape, automatically eject the tape, and display a lamp indicating the end of the tape. An object of the present invention is to provide a tape stop detection circuit that can improve reliability.

Embodiments of the present invention will be described in detail below with reference to the drawings.

FIG. 1 shows an embodiment in which an automatic reversing mechanism is activated by tape end detection.

In the figure, numeral 1 denotes a switch that is turned on and off while the tape is running, and is provided on a tape drive system component, such as a reel stand.

9 and 10 are resistors, and 11 is a capacitor.

13 has a threshold-hold level, and when the voltage applied to the threshold terminal LK exceeds the threshold level, the function oscillates a pulse in the cycle of time 1 from when the input pulse disappears to the threshold-hold voltage. This is an oscillation circuit having an oscillation circuit, and is formed by, for example, an HA 17555 IC.

14 is a capacitor with a larger capacity than capacitor 11,
It is connected to the threshold voltage of the oscillation circuit 13, and when the voltage Ec of the capacitor 14 becomes higher than the threshold voltage, a pulse signal is oscillated from the output terminal OUT of the oscillation circuit 13.

The output terminal OUT is always at a high level through the oscillation circuit.
The button is set to H'', and the oscillation causes the low level (I L''
fall into.

The capacitor 14 has the function of supplying DC power of a predetermined voltage to the oscillation circuit 13, and therefore the oscillation circuit 13
An independent DC power supply circuit to drive the is not required.

A resistor 15 is connected between the strain hold terminal of the oscillation circuit 13 and the discharge terminal DIS.

This DIS terminal is connected to a power source 17 via a resistor 16.

Further, the power supply terminal Vcc is also connected to the power supply 17, and the reset terminal R8 is also connected to the power supply 17 via the resistor 18.

Similarly, the control charge terminal C is capacitor 1
9 to the ground, and the ground terminal E to the ground.

Furthermore, when R8 is grounded, OUT also falls to I (Ljj).

According to this, it is also possible to stop the operation manually.

21 is an electromagnet for operating the tape reversing mechanism of the tape recorder, and is connected between the collector of the transistor 20 and the ground, and the emitter of the transistor 20 is connected to the power source 1.
7, the base is connected to the output terminal OUT of the oscillation circuit 13.

22 is a resistor, 23 is a capacitor, and a manual switch 24 is provided between the intermediate point between the resistor 22 and the capacitor 23 and the capacitor 14.

Next, the operation of the above device will be explained.

The capacitor 14 is charged with the electric charge of the power source 17 via the resistor 16.degree. 15.

While the tape is running, switch 1 is turned on and off repeatedly.

By repeatedly turning on and off the switch 1, the capacitor 14 is repeatedly charged and discharged in the next operation.

That is, when switch 1 is turned on, capacitor 14
charges the capacitor 11 through the diode 12 and is discharged through the switch 1 and through the diode 12, the resistors 10 and 9, and the switch 1.

When the switch 1 is turned off, the charges in the capacitor 11 become the same potential through the resistors 9 and 10, are discharged through the resistors 9 and 10, and are reverse biased by the resistor 10, so the diode 12 becomes non-conductive and the charge in the capacitor 14 does not flow out. 16. Charge gradually through 15 minutes.

While the tape is running, the switch 1 is constantly turned on and off, and the capacitor 14 is repeatedly charged and discharged as shown in FIGS. 2 and 3, so that the waveform of the terminal voltage becomes sawtooth.

Therefore, if the maximum charging value of the capacitor 14 during this period is set to be less than the threshold voltage of the oscillation circuit 13, no pulse will be oscillated from the output terminal OUT of the circuit 13.

When the end of the tape is reached and the tape stops running, the switch 1 is turned on or off to stop.

When the switch 1 is stopped in the OFF state, the diode 12 becomes non-conducting due to the reverse bias applied to the diode 12 through the resistor 10, and the capacitor 14 connects the resistors 16 and 15 as shown in FIGS. continues to be charged through.

When the capacitor 11 is stopped in the on state, it is charged via the resistor 10, and the voltage makes the diode 12 non-conductive, so the capacitor 14 is similarly charged via the resistor 16.15 as shown in FIGS. 2 and 3. continues to be.

When the voltage EC of the capacitor 14 exceeds the threshold level of the oscillation circuit 13, the output terminal OUT of the oscillation circuit 13 changes from H'' to 'L'' and the charge of the capacitor 14 is discharged through the DIS terminal.

The oscillation period of the oscillation circuit 13 is set by the time constants of the resistors 15 and 16 and the capacitor 140, and the pulse width of the old oscillation pulse is set by the time constants of the resistor 15 and the capacitor 14.

Specifically, the circuit constants are selected so that a pulse with a width of 0.1 seconds is oscillated from the output terminal OUT 5 seconds after the on/off signal of the switch 1 stops.

This pulse signal (I Ljj is input to the base of the transistor 20, the transistor 20 is turned on, and the electromagnet 2
1 operates to automatically reverse the tape.

When the tape drive direction is reversed and the drive system parts rotate again, the on/off signal of the switch 1 is repeated again as shown in FIG.
repeats charging and discharging, and since the oscillation circuit 130 threshold level is not exceeded, the output of the output terminal OUT is H''11.
is maintained.

In this way, when the switch 1 stops at the end of the tape in the on or off state, the capacitor 14 is charged, and after a predetermined period of time, the oscillation circuit 13 oscillates a pulse signal and automatic reversal is performed, but once due to a malfunction in the automatic reversal operation. If it does not operate with the pulse of
5 as shown in FIG. 3, and when the voltage Ec exceeds the threshold level, a pulse is again oscillated from the output terminal OUT of the oscillation circuit 13 and a repetitive operation is performed, and the electromagnet 21 is activated to automatically Continue in the trench where the inversion takes place.

That is, the portion 30 surrounded by the dotted line operates as an astable multivibrator that outputs pulses at predetermined intervals when the ON/OFF repeating signal is no longer input to the input terminal IN of the oscillation circuit 13.

Also, if you want to perform manual reversal instead of automatic reversal,
When the switch 24 is turned on, the capacitor 14 is charged to the voltage E.

Since exceeds the threshold level, inversion can be performed in the same way.

In this embodiment, an oscillation pulse is used as a trigger to operate the electromagnet 21 via the transistor 20, but since the output of an IC having this oscillation circuit is strong, it is not necessary to directly actuate the electromagnet 21 as a driver IC. You can also do it.

The next figure shows the case where it is also used as an operation signal for an automatic eject mechanism.

FIG. 4 shows an embodiment thereof, in which the output terminal O of the oscillation circuit 13
UT tape cassette automatic eject mechanism electromagnet 2
5 directly connected.

While playing the tape, when the cassette is in the installed position, electromagnet 2
5 is energized, and at the end of the tape, the output becomes H after the tape is stopped.
When changing from "L" to "L", the electromagnet 25 is turned off, the cassette is ejected, and the power is turned off.

The switch 26 is a manual eject switch, and by grounding the reset terminal R8 of the oscillation circuit 13, the output terminal is lowered from H'' to L'', the electromagnet 25 is turned off, and the cassette is ejected.

Note that 21 is a resistor and 28 is a capacitor. Manual ejection can also be performed by providing a switch between the output terminal OUT of the oscillation circuit 13 and the plunger 25 and turning off the switch instead of grounding the reset terminal R8.

The circuit shown in FIG. 5 shows another embodiment of this circuit.

The resistor 10 is converted into a diode 10' in the detection circuit.

During fast forwarding, the reel stand rotates faster and switch 1 is turned on.
The cycle of turning off is quick, so the number of pulses is large, and it is difficult to be discharged, so the charging potential rises and it becomes easier to reverse 1.
Therefore, by replacing the resistor with a diode, the discharging action can be performed completely, and this can be applied even when the reel table rotates quickly during fast forwarding.

Similarly, in Figure 4, if a resistor is used, the reset may not be completely shut down and a malfunction may occur, so if the resistor 18 is replaced with a diode 18' in the reset circuit, it can be set to the ground level completely. I can do it.

In addition, the manual circuit shown in Figure 1 causes a time lag when the switch is pressed for a long time during manual operation, causing trouble in timing the operation, so Figure 4 shows the manual switch connected to the R8 terminal. be.

As described above, according to the embodiment of the present invention, a pulse of a predetermined width is output when the tape end is detected, and this pulse can be used for desired purposes, such as automatic reversal, automatic ejection, etc. You can also have them do this.

According to the present invention, the tape stop detection circuit includes a switch that is linked to a tape drive mechanism and repeatedly opens and closes while the tape is running:
During opening and closing of the switch, charging and discharging are repeated through the capacitor and diode, and the constant charging voltage is not reached, and when the switch stops opening and closing, discharging is stopped through the capacitor and the diode, and the battery is charged at a voltage exceeding a constant voltage of 1. It has a capacitor and a varnish threshold level, and when the charging voltage of the capacitor reaches the constant voltage and exceeds the threshold level, it is discharged to obtain an oscillation output, and the capacitor and resistor control the oscillation operation and oscillation period. Since the capacitor is equipped with an oscillation circuit that obtains Not only can the operation be simplified, but also the reliability of operation can be improved.

If a commercially available IC is used for the oscillation circuit 13, a tape stop detection circuit can be obtained by simply adding a simple detection circuit such as a capacitor and a resistor to the IC.

[Brief explanation of drawings]

FIG. 1 is an electric circuit diagram showing an embodiment of the present invention, FIGS. 2 and 3 are waveform diagrams for explaining the operation of the embodiment, and FIGS. 4 and 5 are other embodiments of the present invention. FIG. 3 is an electrical circuit diagram illustrating an example. DESCRIPTION OF SYMBOLS 1... Tape running interlocking switch, 11.14... Capacitor, 12... Diode, 13... Oscillation circuit, 15.16... Resistor, 20... Transistor, 2
1゜25...Electromagnet.

Claims (1)

[Scope of utility model registration request] A switch 1 that is linked to the tape 1 drive mechanism and repeats opening and closing while the tape is running; and a capacitor 1 while the switch 1 is opening and closing.
When the capacitor 14 repeatedly charges and discharges through the diode 12 and does not reach a constant charging voltage, the capacitor 14 stops discharging through the capacitor 11 and the diode 12 when the switch 1 stops opening and closing, and is charged at a voltage exceeding the constant voltage. When the charged voltage of the capacitor 14 reaches the constant voltage and exceeds the threshold level, it is discharged and an oscillation output is obtained. and an oscillation circuit 13 for obtaining an oscillation period.