JP2532222B2 - Information display device - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION [Industrial application] The present invention relates to an information display device using a light emitting diode, and is mainly used outdoors.

[Conventional technology]

Conventionally, an information display device using a light emitting diode as a display element has been used. This is one in which light-emitting diodes are arranged in a matrix and letters, figures, etc. are displayed by dot-spacing, and one in which light-emitting diodes having different emission colors are combined and displayed in a mixed color is also proposed.

[Problems to be solved by the invention]

By the way, as shown in FIG. 2, when the light emitting diode is displayed for a long time, the light emission output is reduced due to deterioration with time, but the reduction amount is different depending on the material forming the light emitting body of the light emitting diode. . For example, the GaAlAs red light emitting diode exhibits the characteristics of the symbol "a" in FIG.
The yellow light emitting diode of the above shows the characteristic of the symbol "b". Therefore, when the information display device is used for a long time, the amount of light emitted from the light emitting diode changes, and particularly in a display device in which different emission colors are mixed, the degree of mixing of the emission colors changes, which causes a problem in visibility. Further, when the information display device is installed on the road to display road information etc., the display surface of the light emitting diode becomes dirty due to the exhaust gas of the passing vehicle, the surrounding dust, etc., and the light output decreases, but the decrease The degree depends on the installation environment of the information display device. For example, if it is installed in a place where the display surface of the light emitting diode is naturally cleaned by being exposed to wind and rain, as shown by the symbol "a" in FIG. The amount of light decreases, but after that, the amount of light decreases gradually, and the amount of light emission becomes constant over time. Also, when installed in a place where natural cleaning cannot be expected, such as in a tunnel, where it is not exposed to wind and rain, dirt accumulates as shown by the symbol "b" in Fig. 3 and the amount of light changes as the years pass. descend. In any case, the reduction of the light output of the light emitting diode has a great influence on the visibility.

Further, when the information display device is installed outdoors, it is exposed to sunlight, so that the transparency of the transparent resin (usually an epoxy resin) on the surface of the light emitting diode is reduced by the ultraviolet rays, and the amount of emitted light is reduced. There is also a problem that the dust or the like damages the surface of the light emitting diode, reduces the amount of emitted light, and reduces visibility.

[Means for solving problems]

In order to solve such a problem, the present invention provides a first timer that counts time only while a light emitting diode is lit, and a second timer that performs a normal clock time and initializes a count output value according to a predetermined operation. , The light amount reduction of the light emitting diode due to the time-dependent deterioration of the light emitting diode is corrected according to the timed output value from the first timer, and the display surface of the light emitting diode is soiled according to the timed output value from the second timer. And a control circuit for correcting a decrease in the light amount of the light emitting diode.

Further, the control circuit is independently provided for each light emission color of the light emitting diode.

[Action]

The light amount that decreases with the passage of time is corrected by the control circuit based on the count value of the timer, and a constant light amount is secured.

〔Example〕

FIG. 1 is a block diagram showing an embodiment of the present invention, which is an example in the case of one kind of emission color. In the figure,
Reference numeral 1 denotes a timer which measures the operation time only when the display switch 2a is on, and does not measure the operation time when the display switch 2a is off. Based on the output of the timer 1, the control circuit 3 corrects the decrease in the emitted light amount shown in FIG. 2 and causes the light emitting diode 4 to emit a constant amount of light when the display switch 2b interlocking with the display switch 2a is turned on. It has become.

Now, when the output value of the timer 1 represents 1000 hours, the relative light emission amount of the red light emitting diode is 0.9 which is the initial value as shown in FIG. 2, so the control circuit 3 does not control to correct the decrease. The luminous intensity of the light emitting diode 4 is controlled so that the luminous intensity is increased by 1 / 0.9 = 1.1 times of the time. As one method thereof, since the amount of light emitted from the light emitting diode depends on the flowing current, it is conceivable to increase the amount of emitted light by increasing the current.

FIG. 4 is a graph in which the horizontal axis represents the current of the light emitting diode and the vertical axis represents the relative light emission amount. The red light emitting diode indicated by the symbol “a” has a relative light emission amount of 1.0 when the initial current value is I. Then, the relative light amount becomes 1.1 by increasing the current value by ΔI1. Therefore, when the usage time exceeds 1000 hours, the same amount of light as the initial amount of emitted light can be secured by increasing the current supplied to the light emitting diode by ΔI1 from the initial value I.

Reference numeral 5 in FIG. 1 is a timer which always measures time and which is reset when the reset switch 6 is pressed to be in the initial state. The control circuit 3 also controls the light quantity of the light emitting diode based on the output of the timer 5. If the output value of timer 5 indicates 2 years,
Assuming that the installation location of the information display device is a location where natural cleaning is performed by wind and rain, the relative light amount is 0.8 when the initial value is 1, according to the characteristic "a" in FIG. At this time,
If the value of timer 1 indicates 1000 hours, the relative light emission amount of the red light emitting diode at that time is 0.9 from FIG.
Is. Therefore, the relative amount of luminescence considering both conditions is
0.9 x 0.8 = 0.72. Therefore, the control circuit 3 changes the relative light amount
The current supplied to the light emitting diode is increased by ΔI2 so that 1 / 0.72 = 1.39. As a result, a decrease in the amount of light emitted from the light emitting diode due to a change with time and a decrease in the amount of light emitted due to stains can be corrected.

Here, when the surface of the light emitting diode is cleaned by performing regular maintenance and the reset switch 6 is turned on, the timer 5 resets the count value so far. Therefore, the value of the timer 5 is in the initial state, and the control circuit 3 only corrects the deterioration with time. However, when the light emitting diode becomes dirty again after a lapse of time, the correction due to the dirt is also performed.

FIG. 5 shows an example in which light emitting diodes having different display colors are used. Reference numeral 7 is a control circuit for controlling the yellow light emitting diode 8 based on the outputs of the timers 1 and 5, and the switch 2c is a switch.
It is linked with 2a and 2b. Here, when the display time is 1000 hours, the control circuit 3 performs the above operation, and when the control circuit 7 does not consider the output of the timer 5, the initial stage of the yellow light emitting diode indicated by the symbol "b" in FIG. In order to correct the relative light emission amount of 0.7 when the value is 1, the light amount of the yellow light emitting diode 8 is controlled to be increased by 1 / 0.7 = 1.43 times.
That is, the current of the yellow light emitting diode 8 is controlled so as to be increased by ΔI3, as indicated by the characteristic "B" in FIG. The above is the operation when the output of the timer 5 is not taken into consideration. However, when the timer 5 outputs a value representing two years, the relative light emission amount is set to an initial value of 1 from the characteristic "a" in FIG.
Since it is 0.8, a reduction of 0.8 × 0.7 = 0.56 is obtained when a reduction of 0.7 in the relative light emission amount due to deterioration over time is taken into consideration. For this reason, the control circuit 7 controls the yellow light emitting diode 8 so as to increase the amount of light emitted by the yellow light emitting diode 1 / 0.56 = 1.79 times that in the non-controlled state in order to correct this decrease. That is, the fourth
As shown in the characteristics of symbol B in the figure, the yellow light-emitting diode 8
The current is controlled to increase ΔI4. As described above, even when light-emitting diodes of different display colors are used for display, the amount of light emitted from each light-emitting diode can be kept constant, so that a constant mixing ratio can be secured.

In the above embodiments, the display color of the light emitting diode is one or two, but three or more colors may be used, and the display colors may be those other than those in the embodiments. The control of the amount of light emitted from the light emitting diode based on the value of the timer has been described to be continuously controlled corresponding to the graph such as the characteristics of the light emitting diode. However, the value of the timer is divided into steps and controlled. You can also The current value of the light emitting diode can be controlled by the applied voltage, by limiting the current, or by controlling the pulse width of the current passed through the LED. It is possible to provide a power outage guarantee for the timer so that it can keep time even during a power outage. In FIG. 5, the timer 1 for measuring the usage time is shared by the red and yellow light emitting diodes, but when the display times of the respective light emitting diodes are different, it is necessary to provide each of the light emitting diodes.

〔The invention's effect〕

As described above, according to the present invention, the amount of light emitted from the light emitting diode is controlled according to the operating time of the timer that counts time, so that it is possible to perform a display in which the amount of light emitted is kept constant over time. Has the effect.

[Brief description of drawings]

FIG. 1 is a block diagram showing an embodiment of the present invention, FIG. 2 is a graph showing characteristics of deterioration of a light emitting diode with time, and FIG.
FIG. 4 is a graph showing a change with time in the amount of emitted light due to contamination due to the installation state of the light emitting diode, and FIG. 4 is a graph showing characteristics of current supplied to the light emitting diode and relative amount of emitted light,
FIG. 5 is a block diagram showing another embodiment. 1,5 …… Timer, 2a, 2b, 2c, 6 …… Switch, 3,7 …… Control circuit, 4,8 …… Light emitting diode.

Claims (2)

(57) [Claims] 1. An information display device for displaying predetermined information by means of a light emitting diode, wherein a first timer for counting time only while the light emitting diode is lit, and a constant time clock and initialization of a clock output value in response to a predetermined operation. And a second timer for correcting the decrease in the light amount of the light emitting diode due to the time deterioration of the light emitting diode according to the time output value from the first timer, and the light emitting diode according to the time output value from the second timer. An information display device, comprising: a control circuit that corrects a decrease in the light amount of a light emitting diode due to dirt on the display surface. 2. The information display device according to claim 1, wherein the control circuit is provided independently for each light emission color of the light emitting diode.