JPH0411231Y2 - - Google Patents

Description

[Detailed description of the invention] [Industrial field of application] This invention is a video tape recorder (VTR) equipped with a tape counter, and when this counter reaches a predetermined value during fast forwarding or rewinding, This invention relates to a memory stop circuit for stopping tape running.

[Prior art]

If you want to play a certain program (on a VTR) repeatedly, reset the tape count to zero at the beginning of the program and start playback, then rewind when the program ends and start the counter. It would be convenient if the tape could be configured to automatically stop when the value becomes zero, and furthermore, to automatically start playing. For this reason, in the past, a mechanical or electronic counter (for example, counting the rotations of the take-up reel) was provided, and when the counter reached a predetermined value (which could be set externally), the tape stop counter was installed. It is designed to output a signal.

However, if the tape stop signal is output at the point when the tape is desired to be stopped, there is a drawback that the tape will be rewound too much due to the inertia of the tape drive system. In order to correct this and stop the tape at a desired position, the tape stop signal may be output at a timing slightly earlier than the desired position, taking into consideration the inertia of the tape drive system. However, the inertia of the tape drive system is not constant and changes depending on the beginning and end of tape winding (i.e., changes in the tape winding diameter), or the amount of tape being rewound, so it is impossible to stop the tape accurately. Have difficulty.

[Purpose of invention]

The present invention has been developed in view of the above points, and an object of the present invention is to provide a memory stop circuit with an accurate stop position.

[Structure of the idea]

The present invention includes an up-down counter section that increases and decreases in relation to tape running, a detection section that detects the tape winding diameter, and a stop signal output section that inputs the output of the counter section and the output of the detection section and outputs a tape stop signal. The memory stop circuit is characterized in that the generation timing of the tape stop signal changes depending on the output of the detection section.

〔Example〕

An embodiment of the present invention will be described with reference to the circuit block diagram of FIG. In the figure, 1 is an up-down counter section, 2 is a tape winding amount detection section, and 3 is a stop signal output section. Signals (reel rotation pulses) related to the rotation of each reel stand are applied to the up-down counter section 1 via amplifiers 4 and 5 from a take-up reel stand sensor 6 and a supply reel stand sensor 7. The up-down counter section (hereinafter referred to as the counter section) 1 is composed of a microcomputer (CPU), and is not just a counter, but also has the function of calculating the remaining amount of tape based on the signals from each reel stand. The display means 8 displays the contents of the counter section 1 (tape count value, remaining amount time, etc.).

When the counter section 1 operates as a tape counter, it counts the rotations of either the take-up reel or the supply reel. Whether to up-count or down-count the signal from the reel stand is instructed to the counter section 1 using a mode signal from a system control circuit (not shown) of the VTR. SW ₁
resets the contents of counter section 1 (to "0000")
This is a reset switch for Counter part 1
The outputs S ₁ to _{S 3} are respectively outputs that are high level when "0000", outputs that are high level when "0010", and outputs that are high level when "0030",
The stop signal is applied to the stop signal output section 3 .

The output of the take-up reel stand sensor 6 is also applied to the tape winding amount detection section 2 . The detection unit 2 includes a monostable monomultivibrator MM9 triggered by the output of the sensor 6, an AND gate 10 inputting the output a of the MM9 and the output of the sensor 6, and the
The first EX-OR gate 11 receives the AND gate 10 output b and the sensor 6 output, and the 1st EX-OR gate 11 receives the AND gate 10 output b and the MM9 output a.
It consists of a 2EX-OR gate 12 and an RS-flip-flop (RS-FF) 13 whose reset input R is the output c of the first EX-OR gate 11 and whose set input S is the output d of the second EX-OR gate 12.

The stop signal output section 3 receives the "0000" output, "0010" output, "0030" output and RS from the counter section 1 .
-Output e of FF13 is supplied. Stop signal output section 3 outputs RS-FF13 output e and "0030"
AND gate 14 with output _S3 as input and "0000"
An OR gate 15 whose inputs are the output S ₁ , the "0010" output S ₂ and the AND gate 14 output f, and whose inputs are the output of the inverter 16 connected to the output of the OR gate 15 and the memory stop switch SW ₂ .
It consists of an AND gate 17, and the output of the AND gate 17 becomes the stop signal S (for example, input to the system control circuit).

It has been found through experiments that the condition of the tape drive system (mainly) of a VTR in which the circuit of FIG. 1 is used is as follows.

If you rewind and stop at the beginning of the tape, where the amount of tape wound on the supply reel is large and the winding system is large, the counter will rewind by 30 counts.

If you rewind and stop at the end of the tape, that is, the part where the amount of tape wound on the supply reel is small and the winding diameter is small, the rewind will be 10 counts too long.

This is because the supply reel is driven during rewinding, and the magnitude of inertia varies depending on the tape winding diameter of the supply reel. Therefore, in order to stop the tape at the desired position (count value), it must be stopped 30 counts before the desired count value at the beginning of the tape, 10 counts before the end, and 10 counts before the end. Just output the signal.

In the circuit shown in FIG. 1, the winding diameter of the tape on the supply reel is detected by the rotation period of the take-up reel. This is because the supply reel is driven at approximately constant rotation during rewinding. Because the take-up reel rotates quickly at the beginning of the tape (the supply reel's winding diameter is large, the take-up reel's winding diameter is small, and the number of rotations of the supply reel is approximately constant), as shown in Figure 2 (r). The period of the reel rotation pulse from amplifier 5 is short. The reel rotation pulse r triggers the MM9 at its rising edge, and the output of the MM9 becomes something like a. Output a
The high level period τ is determined by the time constant circuit 18 of the MM9. By inputting the reel rotation pulse r to the detection section 2 , the AND gate 1 of the detection section 2
For the output of 0, the first EX-OR gate 11 such as b
An output like c appears in the second EX-OR gate 12, an output like d appears in the second EX-OR gate 12, the RS-FF 13 is set, and the output e becomes high level.

On the other hand, the counter section 1 performs a down-count operation according to a command from the system control circuit, and the contents of the counter decrease as the reels rotate. When the content of the counter becomes "0030", the output _S3 is output from the counter section 1 , and since the AND gate 14 is open, the stop signal S is ORed.
It is output through gate 15 and AND gate 17.

FIG. 3 shows each waveform at the end of the tape. At the end of the tape, the rotation of the take-up reel is slow, so the reel rotation pulse has a long period like r. At this time, the outputs of each gate and RS-FF are as shown in a to e, and the output _S3 is ignored. When the value is "0010", the counter section 1 outputs an output _S2 , which passes through an OR gate 15 and an AND gate 17 and is output as a stop signal S. _S1 , which is output when the counter value is "0000", is used as a stop signal when the count value at the start of rewinding is 10 counts or less.

In the embodiment of FIG. 1, for the sake of simplicity, the position at which the tape automatically stops from the rewind state is limited to when the counter is "0000". It is easy to set this externally, and at this time, the setting value,
The configuration may be such that the output is output from the counter section 1 10 counts before the set value and 30 counts before the set value (by changing the decoder of the counter section). Furthermore, in the case of Figure 1, the time constant of MM9 is used to determine whether the tape is near the beginning or near the end, but in order to stop accurately, it is necessary to make a more detailed distinction. Bye. Furthermore, the present invention is not limited to memory stops during rewinding.

[Effect of idea]

According to the present invention, since the timing at which the tape stop signal is generated differs depending on the tape winding diameter as described above, it is possible to stop the tape at a desired exact position, which is effective.

[Brief explanation of drawings]

FIG. 1 is a circuit block diagram of an embodiment of the present invention, FIG. 2 is a waveform diagram of the main parts at the beginning of the tape in FIG. 1, and FIG. 3 is a diagram of the main waveforms at the end of the tape. Explanation of main figure numbers: 1 ...up-down counter section, 2 ...detection section, 3 ...stop signal output section.

Claims (1)

[Scope of utility model registration request] An up-down counter section outputs multiple tape stop signals that increase or decrease in relation to tape running and corresponds to a predetermined count value, and the tape winding diameter is determined by comparing the cycle of pulses representing the reel rotation speed with a reference cycle. a detection unit that detects the
and a stop signal output section for inputting a plurality of tape stop signals of the up-down counter section and the output of the detection section to select a tape stop signal, and detecting that the generation timing of the tape stop signal changes depending on the output of the detection section. Features a memory stop circuit.