JPH0137006B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION (Field of Industrial Application) The present invention relates to a tuning point display device for AM and FM receivers.

(Configuration of conventional example and its problems) Fig. 1 shows a conventional device of this type, in which a light emitting diode 14 is used to receive FM and AM signals, and the light emitting diodes 21, 22, and 23 are
This is to move the pointer to get the best tuning point when receiving FM, and is placed on the panel surface or the pointer itself. 1 is the input terminal for the FM intermediate frequency signal,
2 is the FM intermediate frequency amplification section, level detection section, AGC
FM detection IC (NEC's μPC 1167C2
etc.), 3 is a detection coil section, and 4 is a resistor that constitutes a detection circuit, at both ends of which an unbalanced voltage is detected. 5 is an AM intermediate frequency signal input terminal, 6 is an AM detection diode, 7 is a low-pass filter, and 8 is a
Light emitting diode (hereinafter referred to as LED) when receiving FM
14 is a resistor for setting the lighting level, 9 is a buffer diode, 10 and 11 are capacitors for AC grounding, 12 is LED 1 when receiving AM
Resistor 13 is for setting the lighting level of 4.
A switching transistor that drives the LED 14,
14 is a tuning point display LED, 15, 19, 20 are
Current limiting resistor for LED21, 22, 23, 1
6 is a bias resistor, 17 and 18 are buffer resistors, and 21, 22, and 23 are detection characteristics S during FM reception.
The LED indicates the direction in which the pointer should be moved in order to tune to the midpoint of the curve (f ₀ in Figure 2), and 24 indicates two identical DC amplifiers 24a and 24b with built-in ICs (Matsushita Electronics AN6551, 6552, etc.). ), 25 is an AM intermediate frequency transformer, and 26 is a bias resistor.

Next, to simplify the operation explanation, first, IC2
The pin is the output of the signal meter drive circuit, and as shown in FIG. 2A, a voltage proportional to the detection current is output. During FM reception, when completely detuned, the output from the pin of IC2 is zero, and the transistor 13 is off, so the LED 14 does not light up.
Also, since no unbalanced voltage appears across the resistor 4, the output at the pin of IC24 is also zero, so the LED21,
23 does not light up. The LED 22 is always lit when the power switch is on.
Now, when you turn the tuning knob and the pointer is at the position corresponding to f ₁ and f ₂ in Figure 2, the FM detection method of IC2 is quadruple detection, and it is composed of balanced differential type switching elements. As a result, the voltage across the resistor 4 becomes unbalanced, a positive voltage appears at the output of the pin of the IC 24, and the LED 21 lights up, instructing the pointer to move further to the right. At this time IC
Since a positive voltage also appears at the output of pin 2, the transistor 13 is turned on, and the LED 14 is also turned on. Conversely, when it is between f ₃ and f ₄ in Figure 2, the polarity of the unbalanced voltage across resistor 4 is reversed, and the IC
Since a negative voltage appears on pin 24,
LED23 lights up, instructing to move the pointer to the left. At this time as well, LED14 lights up. Then f ₂
and f ₃ , especially at the point f ₀ , since the output of the pin of IC 24 is at zero potential, both LEDs 21 and 23 are not lit, and only LED 14 is lit, indicating that the best tuning point is reached. On the other hand, during AM reception, the output of the pin of IC24 remains zero, so the LED21,
Both 23 and 23 do not light up. The tuning point can be known only by lighting the LED 14.

However, in this conventional device, FM,
When receiving AM signals and listening to music, LEDs 14 and 22 are only lit, so the display effect is poor and all
LEDs are underutilized. Another drawback was that it was difficult to judge whether or not the system was in sync.

(Object of the Invention) In view of the drawbacks of the above-mentioned conventional examples, the present invention provides FM,
Even when receiving AM signals and listening to music, the tuning of FM and AM receivers makes full use of LEDs to constantly display a moving display to create a display effect, while at the same time making it easy to understand the tuning status. A point display device is provided.

(Structure of the Invention) The present invention comprises three switching elements that are sequentially driven with different switching times by the output of an astable multivibrator, and five switching elements that are arranged on a panel surface and that blink with the three switching elements. This light-emitting element and this light-emitting element row light up and run from both ends toward the center during FM and AM tuning.
It consists of a control circuit that controls the lights to run in the direction of moving the pointer to achieve the best tuning point when receiving FM.

Hereinafter, embodiments will be described in detail with reference to the drawings.

(Description of Embodiment) FIG. 3 shows an embodiment of the present invention.
Components with the same reference numerals as in FIG. 1 indicate the same components. The 24a side of IC24 is resistor 38, 39, 4
0 and a capacitor 41 constitute an astable multivibrator, which uses two positive and negative power supplies. Therefore, the output signal from the pin becomes a pulse signal as shown in FIG. 5, which spans positive and negative directions with OV as the center. On the positive side of this output signal, transistor 46 is turned on, and then transistor 47 is turned on with a slight delay due to a time constant formed by resistor 43 and capacitor 44. Then, in order to turn on the transistor 48 on the negative side, if the time constants of the resistor 43 and capacitor 44 are selected to appropriate values, the transistors 46, 47, and 48 will change from 46 to 4.
Switching is performed in the order of 7 → 48, and the on/off is repeated in sequence. The pin of IC2 is the output of the muting circuit, and the output shown in FIG. 4A is obtained. That is, the output of the pin of IC2 has completely opposite characteristics to that of the pin. Now, when the reception band is in the FM position and completely detuned, there is enough voltage at the pin of IC2 to turn on transistor 27, and transistor 28 is turned off, so all LEDs 52 to 56 are turned on. It remains gone.

Next, when the tuning knob is operated to enter the range f ₁ to f ₂ in Figure 4, the voltage at the pin of IC2 drops, turning off transistor 27 and turning on transistor 28, but the output at the pin of IC24 Since a positive voltage appears on transistor 32, transistor 32 is turned off.
5 is turned on, transistor 30 is turned on, and transistor 33 is turned off. Therefore, LED52,
Since power is supplied only to the three on the left side of 53 and 54, the switching action of the transistors 46, 47 and 48 causes the LEDs to light up in sequence from 52 to 53 to 54, thereby moving the pointer on the dial display surface to the right. instruct. Conversely, when the range is between f ₃ and _{f 4} , the transistor 28 is turned on as described above, but the output of the pin of the IC 24 is a negative voltage, so the transistor 32 is turned on.
Transistor 35 is off, transistor 30 is off, transistor 33 is on, and LED5
Power is supplied only to the right three LEDs 4, 55, and 56, and they light up sequentially in the order from LED 56 through 55 to 54, instructing to move the pointer to the left. When the range is between f ₂ and _{f 3} including the best tuning point f ₀ , the transistor 28 is also turned on, and the voltage across the resistor 4 is in a balanced state.
The output of the pin of IC24 becomes zero potential, transistors 32 and 35 are both turned off, and transistor 3
Both 0 and 33 are on. Therefore, LED52~5
Power is supplied to all LEDs 6, and the LEDs 52 to 56 are turned on in sequence from 53 and 55 to 54 (running from both ends to the center) to indicate the best tuning point.

When the receiving band is set to AM and when completely detuned, transistor 57 is off and transistor 27 is off.
Since the transistor 28 is turned on, the transistor 28 is turned off, and the LEDs 52 to 56 are all turned off. In the tuned state, transistor 57 is turned on, transistor 27 is turned off, and transistor 28 is turned on. During AM reception, the output from the pin of the IC 24 remains zero, and the transistors 30 and 33 remain on as at the FM best tuning point, so power is supplied to all LEDs 52 to 56 during AM tuning. Therefore, just like when tuning to FM, the lights run from both ends toward the center, indicating that it is in tune.

(Effects of the Invention) As explained above, according to the present invention, it is possible to provide an excellent display effect by providing a moving display even when the tuning is in use, and it is possible to make the tuning state very easy to understand. There is an effect that can be done.

Note that although LEDs are used in this embodiment, similar effects can be obtained by using lamps or other display elements. Furthermore, by changing the values of the resistors and capacitors that make up the astable multivibrator, the oscillation frequency can be changed and the lighting speed of the LED can be changed arbitrarily.

[Brief explanation of drawings]

FIG. 1 is a circuit diagram of a conventional example, FIG. 2 is an explanatory diagram of the same operation, and FIG. 3 is a circuit diagram of an embodiment of the present invention.
FIG. 4 and FIG. 5 are operation explanatory diagrams. 2...FM detection IC, 3...FM detection coil section,
6...AM detection diode, 24...IC including two DC amplifiers, 28, 30, 33, 46, 4
8...Switching transistor, 38, 39,
40... Resistor forming an astable multivibrator, 41... Capacitor, 43, 44... Resistor and capacitor forming a time constant circuit, 52,
53, 54, 55, 56...LED for display.

Claims (1)

[Claims] 1a Three switching elements 46, 47, 4 driven by the output of an astable multivibrator
8, the first and second switching elements 46 and 47 are composed of NPN transistors, and an appropriate time constant circuit is provided at the input of the second switching element so that the switching operation is performed more temporally than the first switching element. causing a delay and further delaying the third
A light emitting element driving means configured to sequentially perform a switching operation in three stages using a PNP transistor as the switching element 48 of b. Five light emitting elements 52, 53, 5 on the panel surface.
4, 55, and 56 are arranged in a line, and the cathodes of the two light emitting elements at both ends of the light emitting element line are connected in common to the first switching element, and each second light emitting element from the end of the light emitting element line is connected to the first switching element. The cathodes of the two elements are connected in common to the second switching element, and the cathode of the central light emitting element of the light emitting element row is further connected to the third switching element to perform lighting operation of the light emitting element row. a display means configured to run from both ends toward the center; c. connecting the anodes of two light emitting elements in order from one side of the light emitting element array to the first power switching element 30 in common; Starting from the other side, the anodes of the two light emitting elements are commonly connected to the second power switching element 33, and the first
and the respective input sides of the second power switching element and the anode of the central light emitting element are commonly connected to the output side of the third power switching element 28, and the first and second switching elements are connected to each other.
The third power switching element is also activated by the output of the unbalanced voltage detection circuit of the FM detection circuit.
FM, The lighting movement of the light emitting element array is performed when tuning an AM signal, and the direction in which the pointer should be moved to obtain the best tuning point is made clear by the lighting movement of the light emitting element array when receiving an FM signal. A tuning point display device for FM and AM receivers, which is characterized by: