JPS6013629B2 - Control signal receiving circuit - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a receiving circuit using a mechanical filter for receiving a remote control signal from a monitoring device such as a telemeter device or a dam discharge alarm device.

Conventionally, this type of circuit is constructed as shown in Fig. 1, in which 1 is an input terminal for a control signal, 2 is an amplifier for amplifying the control signal from the input state 1, and 3 is an amplifier for receiving the control signal. Mechanical filter that is only sensitive to frequency, 4
is an amplifier that amplifies the output from the mechanical filter 3; 5 is a rectifier circuit that converts the AC voltage from the amplifier 4 into a DC voltage; 6 is a Schmitt trigger circuit that shapes the waveform of the DC voltage from the rectifier circuit 5; 7 is the output terminal. In order to explain the drawbacks of the conventional circuit, the characteristics of the mechanical filter are shown in FIGS. 2a, b and c. When a signal is applied to the mechanical filter 3 for the length of time T shown in FIG. 2a, the response waveform becomes the waveform shown in FIG. 2b. When this is amplified by the amplifier 4 and rectified by the rectifier circuit 5, a waveform shown in FIG. 2c is obtained. Since the response waveform of the mechanical filter 3 has a residual characteristic as shown at 8 in FIG. 2b, the waveform in FIG. 2c also becomes 9. Therefore, if the trigger level of the Schmitt trigger circuit 6 in FIG. 1 is adjusted to level 11 as shown at 10' in FIG. However, if this trigger level is adjusted to level 13 as shown in FIG. 3a, the output Satoko 7 will have a waveform at time t shown in FIG. 3b. Further, when the trigger level is adjusted to level 14 as shown in FIG. 4a, the output state 7 becomes the waveform of the timer as shown in FIG. 4b. The fact that the output time t changes depending on the trigger level in this way means that even if the trigger level is constant, the output time t of the same aircraft will change if the input signal level changes. That is, input terminal 1
When the level of the control signal from the output terminal increases and the trigger level becomes relatively equal to level 13 as shown in Figure 3a, the waveform of the output terminal 7 becomes t as shown in Figure 3b'. . Conversely, when the control signal level from input terminal 1 becomes small and the trigger level becomes relatively level 14 as shown in Figure 4a, the waveform of output terminal 7 becomes as shown in Figure 4b. Become. In this way, when the input level changes, the output time t with respect to the input time T of the control signal is t in Fig. 3b,
The output time may exceed the allowable range as shown in Figure 4b.

Therefore, if the control signal transmission line has large level fluctuations due to frequency characteristics or the like, it is necessary to add an AGC circuit to the amplifier 2 in the circuit shown in FIG. However, A.G.C.
Adding a circuit has the disadvantage that it is prone to malfunction due to noise such as voices, and since the characteristics of each mechanical filter vary, even if it is attached to the AGC circuit, it is complicated to adjust the level with amplifier 4. there were. The present invention eliminates the influence of residual characteristics and level characteristics of a mechanical filter, and further increases the level margin without adjustment even without an AGC circuit in response to level fluctuations in a transmission line by adjusting the peak value of an input signal. The trigger level of the Schmitt trigger circuit is automatically adjusted according to the peak value held, and will be explained in detail below with reference to the drawings.

FIG. 5 is a block diagram of an embodiment of the control signal receiving circuit of the present invention, numbers 1 to 7 correspond to FIG. This is because a hold circuit 15 and a diode switch circuit 16 are provided.

FIG. 6 is a wiring diagram of the peak hold circuit 15, diode switch circuit 16, and Schmitt trigger circuit 6, with amplifier A, resistor missing, R2, R3, R4, diode CO. and capacitor C, constitute a peak hold circuit 15, amplifier N, diode DC2 resistor R
5 constitutes a diode switch circuit 16, and a reference voltage as the minimum value of the trigger level is applied from a terminal 18. Next, the operation will be explained using FIGS. 6 and 7.

When the DC-converted voltage from the rectifier circuit 5 is applied to the terminal 17, the voltage divided by the resistors 1 and 2 is applied to the input terminal of the amplifier A, and the diode CO. becomes conductive and the resistance R
3, the capacitor C is charged. The time required for charging is determined by the values of resistor R3 and capacitor C, but if input voltage is applied for a period sufficiently longer than this time constant, capacitor C will be charged to the peak voltage divided by resistor R2. However, when the input voltage decreases, the current is limited by the diode CD, so the voltage across the capacitor C will be held at its peak value. The holding time is determined by the value of the capacitor C and the values of the resistors R3 and R4, and the discharge time constant is selected to be sufficiently longer than t3 in FIG. 7a. Furthermore, when the diode CD becomes non-conductive, the voltage applied to the input terminal on the side of the amplifier becomes the voltage obtained by dividing the voltage of the capacitor C by the resistors R3 and R4.
Assuming that R is sufficiently larger than resistor R3, the voltage drop due to resistor R4 can be ignored. Therefore, when the voltage of the capacitor C is applied to the input terminal of the amplifier A2, if it is larger than the reference voltage from the terminal 18, the diode CD2 becomes conductive and the output voltage of the switch circuit 16 becomes the voltage of the capacitor C. Conversely, when the voltage of the capacitor C is lower than the reference voltage, the diode CD2 becomes non-conductive and the output voltage of the switch circuit 16 becomes the reference voltage. When the output voltage of this switch circuit 16 is the trigger level of the Schmitt trigger circuit 6 and the voltage from the terminal 17 is higher than the trigger level, the output of the Schmitt trigger circuit 6 becomes H level, and the terminal! When the voltage from 7 is lower than the IJ level, the output of the Schmitt trigger circuit 6 becomes L level.

Now, when the voltage shown by the solid line in FIG. 7a is applied to the terminal 17, the trigger level of the Schmitt trigger circuit 6 becomes as shown by the dotted line in FIG. 7a. Here, the crab pressure of 19 is the reference voltage applied from the terminal 18 and is the minimum value of the trigger level. When the voltage at the input terminal 17 becomes higher than the trigger level at point A, the output terminal 7 becomes H level as shown in FIG. 7b.

When the input voltage increases further, the switch circuit 16 at point B
The diode CD2 becomes conductive, and the trigger level becomes a voltage obtained by dividing the input voltage by the resistors R, , R2. When the input voltage decreases at point C, the trigger level changes to peak hold circuit 1.
Retained by 5. When the input voltage becomes smaller than the trigger level at point D, the output terminal 7 becomes L level. 7th
Even if there is a peak of the residual characteristic of the mechanical filter 3, such as 21 in Fig. 7a, the trigger level is still sufficiently maintained as 20 in Fig. 7a, so the Schmitt trigger circuit 6
The output of is not inverted. When the capacitor C of the peak hold circuit 15 completes discharging, the trigger level becomes the reference flea pressure and returns to the state 19. In this way, the output time is L in Figure 7b for the input time of the control signal, that is, T in Figure 7a, and even if the input level becomes excessive, the output time will not be extended as shown in Figure 3b. Without it, there is almost no change.

As explained above, when trying to detect a certain control signal using a mechanical filter, the trigger level is automatically selected according to the level of the control signal by the circuit of the present invention, so the level margin can be expanded. Not only that, but even if there are variations in the characteristics of the mechanical filter, it operates to absorb them, so there is no need to adjust the circuit as in the case of conventional filters.

[Brief explanation of drawings]

FIG. 1 is a block diagram of a subordinate control signal receiving circuit; FIGS. 2, 3, and 4 are waveform diagrams for explaining FIG. 1;
FIG. 5 is a block diagram of the control signal receiving circuit of the present invention, and FIG.
The figure is a wiring diagram of essential parts of the present invention, and FIG. 7 is a waveform diagram for explaining the present invention. 2, 4...Amplifier, 3...Mechanical filter, 5...
... Rectifier circuit, 6 ... Schmitt trigger circuit, 15 ... Peak hold circuit, 16 ...
...Diode switch circuit. Figure 1 Figure 2 Figure 3 Figure 4 Figure 5 Figure 6 Figure 7

Claims (1)

[Claims] 1. An amplifier that amplifies the received control signal, a mechanical filter that is sensitive only to the frequency of the received control signal,
A control signal receiving circuit comprising an amplifier that amplifies the output signal from the mechanical filter, a rectifier circuit that converts the AC voltage from the amplifier into a DC voltage, and a Schmitt trigger circuit that shapes the waveform of the DC voltage from the rectifier circuit,
A peak hold circuit that holds the peak voltage obtained by dividing the DC voltage obtained by the rectifier circuit for a certain period of time, and compares the voltage obtained by the peak hold circuit with a reference voltage and selects the larger one. A control signal receiving circuit comprising: a switch circuit that outputs a voltage as a trigger level; and the Schmitt trigger circuit is driven by the trigger level obtained by the switch circuit and the voltage from the rectifier circuit. .