JPS5819777A - Display device for residual length of tape - Google Patents

Abstract

PURPOSE:To display the residual length of a magnetic tape when it is used, by producing a pulse train having the cycle which varies in response to the rotational frequency of a reel and measuring the cycle to display the residual amount for a player in which the magnetic tape supplied from the reel of one side is taken up by the reel of other side. CONSTITUTION:For a cassette deck 1, the reels RL-A and RL-B are attached to the shafts 4 and 5 respectively along with multipolar magnets 2 and 3. The Halls iC6 and iC7 are set opposite to the magnets 2 and 3. The reference oscillators 9 and 10 produce a reference pulse train SPB of a long cycle and a reference pulse train SPN of a short cycle respectively. The iC6 and iC7 transduce the changes of the N and S poles corresponding to the revolutions of the magnets 2 and 3 into the Hall pulse trains HPA and HPB. These pulse trains are selected by a Hall pulse switching circuit 11. A reference oscillator switching circuit 12 selects the train SPB in the PLAY mode and then the train SPN in the FF. REW mode respectively, and turns on or off successively the light emitting diodes of a display 17 for residual length of the tape in accordance with the residual length of the tape and via a counter 14 and a latching circuit 15.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a device that detects the rotational speed of a reel of a magnetic tape player and displays a change in the rotational speed as the remaining amount of tape.

To detect the rotation of the reel of a conventional magnetic tape player, (1
) The light beam is intermittent by the rotation of the reel shaft, etc., and the intermittent light is received by a CdS light receiving element and detected optically. (2) A switch linked to the reel shaft, etc. is turned on and off and detected electrically. (3) There is a method of electromagnetically detecting the attachment of a magnet to a disc that is linked to a reel shaft or the like. However, the pulse trains generated by these methods are mainly used to detect the end of the tape necessary for automatic reversal, ejection, and stop, and the determination method is simply based on whether or not there is a pulse. . However, since the above-mentioned pulse train includes information on the number of rotations of the reel, it is possible to know the remaining amount of tape at each point in time by using this information.

The present invention has focused on this point, and is characterized by a pulse train whose period changes depending on the number of rotations of the reel, which is applied to a magnetic tape player that winds the magnetic tape supplied from one reel on the other reel. The present invention is characterized by providing means for generating , means for measuring the period of the pulse train, and means for converting the measured period into the remaining amount of tape and displaying it.

This will be explained in detail below with reference to the drawings.

First, the relationship between the number of rotations of the reel and the remaining amount of tape will be explained based on FIGS. 1 and 2. During play, as shown in FIG. 1, the tape TP is pressed against the capstan shaft CAP by the pinch roller PRFC, and the speed at which it passes over the head HD surface is kept constant. At this time, since both the supply side reels RT and -B and the take-up side reel RL-A keep their circumferential speeds constant, their rotation speeds vary depending on the tape winding diameter. As winding occurs and the remaining amount of tape decreases, the number of revolutions of the take-up reel RL-Ald, whose winding diameter increases, decreases, and conversely, the number of revolutions of the supply reel RL-B, whose winding diameter decreases, increases. On the other hand, FF (fast forward), RE
During W (rewinding), the pinch roller PR is released as shown in Figure 2, and the tape TP is moved to the take-up reel R.
It is wound up at a circumferential speed according to the winding diameter of LA. Therefore, when the number of revolutions of the take-up reel RL-A is constant, the number of revolutions of the supply reel RL-B increases as the tape winding diameter on the take-up side increases. The present invention counts changes in the number of rotations (pulse period) and displays the remaining amount of tape.

An embodiment of the present invention will be described below with reference to FIG. The magnetic tape player of this example is of the O/IJ bath type, and uses Hall iC to detect rotation of the reel. In the figure, 1 is an auto-reverse type cassette deck as shown in Fig. 1, and 2 is a glue RL shown in Fig. 1.
Multipolar magnet attached to A, 3 is similarly attached to reel R
L - B (III (7) Multipolar magnet, 4 is the reel axis on the reel RL-A side, 5 is the reel axis on the reel RL-B side, 6 is the hole IC facing the magnet 2, 7 is facing the magnet B) The Hall IC 19 is a reference oscillator that generates a long-period reference pulse train SPB, 10 is a reference oscillator that generates a short-period reference pulse train SPN, 11 is a Hall pulse switching circuit, 12 is a reference oscillator switching circuit, 16 is a delay circuit, 14 1 is a counter circuit with a built-in decoder, 15 is a latch circuit, 16 is a display drive circuit, and 17 is a display such as an LED, a fluorescent display tube, or a liquid crystal.

Hall IC6 and 7 have N according to the rotation of magnet 2.6
Changes in the pole and south pole of the Hall pulse train HPA.

One of these pulse trains is selected by the switching circuit 11 for conversion into HPH. The selection conditions for the switching circuit 11 are as shown in the table below: tape running directions A and B and operation modes PLAY and FF.

It is REV. It should be noted that the Hall pulse to be employed does not have to be as shown in this table, since it is only necessary to obtain a periodic change.

The switching circuit 12 selects the long-period pulse train SPB of the reference oscillator 9 during PLAY, and also selects the FF.

During REW, the short-period pulse train SPN of the reference oscillator 10 is selected. The counter 14 counts the number of reference pulses SP supplied from the switching circuit 12 to the clock terminal CK during one period of the output Hall pulse HP of the switching circuit 11, for example, it is cleared at the rising edge and is cleared again at the next rising edge. Count. If one period of the Hall pulse HP is on the order of several hundred mg, the reference pulse SP is set on the order of ms, for example.

Since the counted value of the counter 14 is transferred to the latch circuit 15 for each period of the Hall pulse HP, in order to ensure this, the clear terminal CL of the counter 14 is transferred to the latch circuit 15 by the delay circuit 13.
The timing of the Hall pulse HP supplied to R is slightly delayed (may be on the μS order) from the timing of activating the latch circuit 15.

The count value of the counter 14 is 1 of pulse HPA or HPB.
Since it is binary data indicating the period, even if it is directly displayed, it is not effective as an indication of the remaining amount of tape. Therefore, the remaining amount of tape indicator 17 is made of a dot-shaped or bar-shaped light emitting diode array, and each light emitting diode LED, .
Consider turning on or off LEDs ED, . For this purpose, it is necessary to decode the count value (binary data) of the counter 14 into a form suitable for driving the light emitting diode array. In this example, this function is made to correspond to the change in the count value of the counter 14 to the remaining tape amount 11 (in order to make the change in the count value of the counter 14 correspond to the remaining tape amount 11), instead of setting the autopsy value to O at the time of clearing, an appropriate value is preset, and an appropriate number of pulses SP is set. For example, when the remaining amount of tape is at its maximum value, the light emitting diodes LED to LEDn are all turned on, and as the remaining amount of tape decreases, the value of δ1 changes by 1.
It is possible to turn off the lights one by one from the next end, and turn off all the lights when the remaining tape amount is zero.

To explain an example of the operation according to Table 17 above, for example, during PLAY in running direction A, the hole pulse HP of the supply reel
B and a long-period reference pulse SPB are used, and the period of the pulse HPB is sequentially counted by a counter 14. The count value of the counter 14 is decoded and latched in the latch circuit 15 every cycle, but the display on the display 17 does not change every cycle; for example, the difference between the maximum cycle and the minimum cycle of the pulse HPB is Each time the count value of the counter 14 changes by a value divided into n equal parts (n is the number of light emitting diodes), it changes gradually. When PLAYing in running direction B, Hall Nokurusu HPA
Use. On the other hand, a short-period reference pulse SPN is used during FF and REW. This is because the period of the Hall pulses HPA and HPB during FF and REW becomes short, so if a long period reference pulse SPB is used, the count value of the counter 14 decreases, and the display on the display 17 decreases. P.L.
This is to prevent a significant difference from occurring during AY. Some cassettes have different reel diameters, but by using Nogles SP with different frequencies, you can deal with the problem.

As described above, according to the present invention, the remaining amount of tape can be indirectly detected and displayed from the pulse train whose period changes according to the reel rotation speed, which is also used to detect the end of the tape. You can easily know the remaining amount of tape at that point.

[Brief explanation of drawings]

1 and 2 are explanatory diagrams of the remaining amount of tape and the number of reel rotations in a magnetic tape player, and FIG. 6 is a configuration diagram showing an embodiment of the present invention. In the figure, RT, -A, and RL-B are reels, TP is a magnetic tape, and 2. '5 is a magnet, 6 and 7 are pole ICs, 1
4 is a counter, and 17 is a display. Applicant Fujitsu Ten Ltd. Iwa patent attorney Minoru Ken Yanagi? small number
Soil Figure 4 Yabi: 1] Toh 71 He -・ 2"

Claims (1)

[Claims] A magnetic tape player that winds a magnetic tape supplied from one reel on the other reel includes means for generating a pulse train whose period changes according to the number of rotations of the reel, means for measuring the period of the pulse train, and the measuring device. What is claimed is: 1. A tape remaining amount display device for a magnetic tape player, comprising means for converting and displaying a tape remaining amount from the cycle of the recorded tape to a remaining amount of tape.