JPH0424773B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION (a) Technical Field The present invention relates to a tape recorder, and more particularly to a detection device for detecting before the end of a tape.

(B) Background Art Cassette tape recorders that use a tape called a cassette tape, which is stored in a container, cannot easily check the remaining amount of tape, so it may suddenly occur during playback or recording. The tape may end, causing discomfort to the user. In order to improve this problem, devices have been developed that detect and notify when the tape approaches its end, but conventional devices only operate accurately when the magnetic tape is running at a specified speed. Therefore, accurate operation could not be performed when the running speed of the magnetic tape was changed.

(c) Object of the Invention The present invention provides a tape end detection device that can operate accurately even when the running speed of the magnetic tape is changed.

(d) Embodiment of the invention The drawing is a block diagram showing an embodiment of the invention. In the figure, 1 is a supply reel shaft, 2 is a switching circuit that turns on and off as the supply reel shaft 1 rotates, and 3 is a first waveform shaping device that shapes the signal obtained from the switch circuit 2 into a pulse signal. 4 is a motor drive circuit, and 5 is a second waveform shaping circuit that shapes a signal obtained from the motor drive circuit 4 according to the number of revolutions of the motor into a pulse signal. The tape recorder according to the present invention is configured so that the running speed of the magnetic tape can be changed by changing the rotational speed of the electric motor using the electric motor drive circuit 4. Reference numeral 6 denotes a timer circuit that outputs an H (high) level signal at a predetermined period for a predetermined period of time, 7 a first AND circuit that receives the output signals of the first waveform shaping circuit 3 and the timer circuit 6, and 8 a This is a second AND circuit that receives the output signals of the two-waveform shaping circuit 5 and the timer circuit 6 as inputs. 9 is a first counter circuit that counts the pulse signal from the first waveform shaping circuit 3 that is input through the first AND circuit 7, and counts the number of pulses Ns within a predetermined time controlled by the timer circuit 6. It has the effect of 10 is a second counter circuit that counts the pulse signal from the second waveform shaping circuit 5 that is input through the second AND circuit 8, and counts the number of pulses Nm within a predetermined time controlled by the timer circuit 6. It has the effect of

Here, the principle of detecting before the tape end of the present invention will be explained. If the signal when the running speed of the magnetic tape is at the specified speed is Nmo, and the signal corresponding to the rotation speed of the supply reel shaft 1 when the magnetic tape is at a predetermined position before the end is Nso, then Nso<Ns. When this happens, the end of the magnetic tape is near. Furthermore, when the running speed of the magnetic tape is changed by varying the rotational speed of the electric motor, the signal N corresponding to the rotational speed of the supply reel shaft 1 before the end of the tape is expressed as N=Nso×Nm/Nmo. Become. Therefore, the condition for detecting that the tape is nearing the end is N<Ns Nso×Nm/Nmo<Ns. Therefore, if Nso<Ns×Nmo/Nm is detected, the running speed of the magnetic tape can be changed. It is also possible to always detect a certain position before the end of the magnetic tape.

In the figure, 11 is a first reference signal generation circuit that generates a signal Nmo when the motor is at the reference rotation speed, 12 is an inverter that inverts the output level of the timer circuit 6, and 13 is the inverter 1.
When the output of the second counter circuit 9 is at H level, it is in an operating state, and the output Ns of the first counter circuit 9 and the second
This is an arithmetic circuit that receives the output Nm of the counter circuit 10 and the output Nmo of the first reference signal generating circuit 11 as input, and has the function of outputting an arithmetic signal of Ns×Nmo/Nm. 14 is the inverter 12
The first counter circuit 9 and the second counter circuit 1 delay the H level signal obtained by
This is a reset circuit that applies voltage to the zero reset terminal. 15 is a signal Nso corresponding to the rotation speed of the supply reel shaft 1 when the running speed of the magnetic tape is at a specified speed state and the tape is at a predetermined position before the end.
This is a second reference signal generation circuit that generates a second reference signal. Reference numeral 16 denotes a comparator circuit that becomes operational when the output of the inverter 12 is at H level and compares the output signal Nso of the second reference signal generation circuit 15 with the output signal Ns×Nmo/Nm of the arithmetic circuit 13. Yes, and when Nso<Ns×Nmo/Nm, an H level detection signal is output to the output terminal 17. 18
is a notification circuit that becomes operational when an H level detection signal is output to the output terminal 17 of the comparison circuit 16, and notifies the user that the end of the tape is near. The present invention is configured as described above,
Next, the operation will be explained.

When the tape recorder is operated for reproduction, the motor drive circuit 4 becomes operational and drives the motor, causing the magnetic tape to run at a constant speed, so that the supply reel shaft 1 starts rotating. When the supply reel shaft 1 starts rotating, the switching circuit 2 turns on and off, and its on/off output is input to the first waveform shaping circuit 3 and shaped into a pulse signal.
Further, the signal obtained from the motor drive circuit 4 is input to the second waveform shaping circuit 5 and shaped into a pulse signal. The pulse signals whose waveforms have been shaped by the first waveform shaping circuit 3 and the second waveform shaping circuit 5 are respectively
The pulse signal is input to the 1AND circuit 7 and the second AND circuit 8, but unless the timer circuit 6 outputs an H level signal, the first AND circuit 7 and the second AND circuit 8 do not output the pulse signal. The timer circuit 6 outputs a signal at H level for a predetermined time T, then outputs a signal at L (low) level for a predetermined time t, and outputs a signal at H level for a predetermined time T. Repeat the action. Therefore, during the T time period when the H level signal is applied from the timer circuit 6 to the output terminals of the first AND circuit 7 and the second AND circuit 8, the input from the first waveform shaping circuit 3 and the second waveform shaping circuit 5 is applied. This will output a pulse signal. The pulse signal output from the first AND circuit 7 is input to the first counter circuit 9 and counted, and the pulse signal output from the second AND circuit 8 is input to the second counter circuit 10 and counted. The first counter circuit 9 counts the pulse signals input during the T period and outputs a count output Ns. Further, the second counter circuit 10 counts the pulse signals input during the T period and outputs a count output Nm. T
When the time elapses, the output of the timer circuit 6 becomes L level, so that the first AND circuit 7 and the second AND circuit 8 do not output pulse signals for the time t. Then, when the output of the timer circuit 6 becomes L level, the output of the inverter 12 becomes H level, so that the arithmetic circuit 13 and the comparison circuit 16 are in an operating state for a period t. Therefore, the arithmetic circuit 13 is the first counter circuit 9
output Ns, output Nm of the second counter circuit 10
and from the output Nmo of the first reference signal generation circuit 11
Outputs a calculation signal of Ns×Nmo/Nm. Further, the comparison circuit 16 performs a comparison operation between the Ns×Nmo/Nm signal from the arithmetic circuit 13 and the signal Nso from the second reference signal generation circuit 15. When there is a large amount of magnetic tape remaining, the rotation speed of the supply reel shaft 1 is small, so Ns×Nmo/Nm<Nso, and an H level detection signal is not output to the output terminal 17 of the comparison circuit 16. . And the output of the first counter circuit 9
After Ns and the output Nm of the second counter circuit 10 are read into the arithmetic circuit 13, the first counter circuit 9 and the second counter circuit 10 are reset by the output signal of the reset circuit 14. In the reproducing operation state, the above-described operations are repeated, and as the magnetic tape is wound, the number of rotations of the supply reel shaft 1 increases. When the tape is wound to a predetermined position before the end of the magnetic tape, Ns×Nmo/Nm>Nso, and an H level detection signal is output to the output terminal 17 of the comparator circuit 16, and the notification circuit 18 is activated, so the user can can recognize that it is nearing its end.

(e) Example of application of the invention In this embodiment, a pulse signal corresponding to the rotation speed of the electric motor is obtained from the motor drive circuit 4, but the rotation of the electric motor is transmitted by a belt and the magnetic tape is driven at a constant speed. It can also be configured to be obtained from the capstan shaft. Also, the notification circuit 1
8 can also light up a light emitting element such as a light emitting diode or sound a buzzer. Further, although the present invention is constructed by the arithmetic circuit 13, the comparison circuit 16, etc., it can be easily constructed by using a microcomputer.

(F) Effect The present invention not only can detect when the magnetic tape approaches its end, but also accurately detect the position before the end of the tape even if the running speed of the magnetic tape is changed. The present invention is most suitable as a tape end detection device for a tape recorder equipped with a function called pitch control.

[Brief explanation of drawings]

The drawing is a block diagram showing one embodiment of the detection device of the present invention. Explanation of main drawing numbers, 1... Supply reel shaft, 3...
First waveform shaping circuit, 5...Second waveform shaping circuit, 6
...Timer circuit, 9...First counter circuit,
10...Second counter circuit, 11...First reference signal generation circuit, 13...Arithmetic circuit, 15...Second
Reference signal generation circuit, 16... Comparison circuit, 18...
Notification circuit.

Claims (1)

[Claims] 1. In a tape recorder in which the running speed of a magnetic tape can be changed from a specified speed by changing the rotational speed of an electric motor, a first pulse signal that generates a pulse signal according to the rotational speed of a supply reel shaft is provided. a pulse signal generation circuit, a second pulse signal generation circuit that generates a pulse signal according to the rotation speed of the electric motor, and a first counter circuit that counts the number of pulses Ns from the first pulse signal generation circuit within a predetermined time. ,
a second counter circuit that counts the number of pulses Nm within a predetermined time from the second pulse signal generation circuit; and a signal Nmo when the motor is at a reference rotation speed.
a first reference signal generation circuit that generates the first reference signal;
An arithmetic circuit that receives signals from the second counter circuit and the first reference signal generation circuit and outputs a signal of Ns×Nmo/Nm, and the number of revolutions of the supply reel shaft when the tape is at a predetermined position before the end. a second reference signal generation circuit that generates a signal Nso according to the second reference signal generation circuit; and a comparison circuit that compares the output signal of the arithmetic circuit and the output signal of the second reference signal generation circuit,
A pre-end detection device for a tape, characterized in that the comparison circuit outputs a detection signal when Nso<Ns×Nmo/Nm.