JPH04360390A - Electronic device for mobile body mount - Google Patents

Abstract

PURPOSE:To attain automatic degaussing of a color CRT only at a required point of time in an electronic device mounted on a mobile body such as a vessel and a vehicle. CONSTITUTION:A comparator 4 compares an amplified signal (b) of a detection signal of a magnetic sensor 1 is compared with a comparison level (c) and a trigger signal generating circuit 5 gives a trigger signal (e) to a degaussing circuit 6 every time the result of comparison of the comparator 4 is inverted. Every time the trigger signal (e) is given to the degaussing circuit 6, an attenuating AC current is supplied to a degaussing coil 7. Every time the azimuth of a mobile body from the North to the South or vice versa, the trigger signal (e) is given to the degaussing circuit 6 and the automatic degaussing is implemented in its timing, then the automatic degaussing is implemented only at a required point of time.

Description

[Detailed description of the invention]

0001

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to electronic equipment equipped with a color CRT and mounted on a moving body such as a ship or a vehicle.

0002

[Prior Art] Generally, in a color CRT display device, a cathode ray tube is magnetically shielded by a shield case made of a magnetic material such as permalloy so that the electron beam is not affected by surrounding magnetism and color shift or color unevenness occurs. has been done. Further, a degaussing coil and a degaussing circuit for flowing attenuated alternating current to the degaussing coil are incorporated to prevent the CRT from being magnetized. Normally, this degaussing circuit is configured to operate only for a certain period of time when the device is powered on or off, so as not to affect the actual display screen. Therefore, normally, once convergence is performed, correct color display without color shift or color unevenness is maintained.

However, when a color CRT is used as a display for electronic equipment mounted on a moving body such as a ship or vehicle, the CRT may
The relative direction and strength of the Earth's magnetic field changes. Therefore, CRTs are likely to be magnetized due to the influence of earth's magnetism. In order to avoid such magnetization during display, conventionally, a degaussing circuit is operated to perform automatic demagnetization at fixed time intervals, for example, during the vertical retrace period of raster scan, or to prevent color shift or color unevenness. Demagnetization was performed manually each time it occurred.

0004

[Problem to be solved by the invention] However, the above-mentioned shield case does not have a high shielding effect against geomagnetism.
Moreover, it has the disadvantage of increasing costs. In addition, devices that perform automatic demagnetization waste power because they are unconditionally demagnetized at fixed time intervals, and degaussing often causes disturbances in the displayed content on the screen during normal use. In addition, in a device in which demagnetization is performed manually, a switch for demagnetization must be operated every time a color shift or color unevenness is noticed, making the operation complicated.

[0005] An object of the present invention is to provide an electronic device to be mounted on a moving body which eliminates the above-mentioned conventional problems by automatically performing demagnetization only when demagnetization is required.

[0006]

[Means for Solving the Problems] Color shift and color unevenness in color CRTs are generally thought to be caused by changes in the orientation (azimuth) of the color CRT and changes in the degree of influence of the earth's magnetic field. Therefore, automatic demagnetization only needs to be performed when there is a change in orientation that causes color shift or color unevenness on the color CRT. The present invention focuses on this point.

[0007] This invention provides a color CRT and a color CRT.
A magnetic sensor that detects magnetism in the external environment in an electronic device mounted on a mobile body equipped with a degaussing circuit that demagnetizes the RT;
Level comparing means for comparing the level of the detection signal from the magnetic sensor with a comparison level; and degaussing instruction signal generating means for generating a demagnetizing instruction signal to the degaussing circuit every time the comparison result of the level comparing means is reversed. It is characterized by having been established.

[0008]

[Operation] In the electronic device mounted on a mobile object of the present invention, the magnetic sensor detects magnetism in the external environment, the level comparing means compares the level of the detection signal from the magnetic sensor with a comparison level, and the degaussing instruction signal generating means , a degaussing instruction signal is given to the degaussing circuit every time the comparison result of the level comparing means is inverted. When the moving object changes its orientation, the detection level of geomagnetism by the magnetic sensor provided in the electronic device mounted on the moving object changes. For example, if a moving object rotates at a constant speed in a horizontal plane, the level of the detection signal of the magnetic sensor changes in a sine wave shape. For example, if the comparison level is 0, the level of the detection signal by the magnetic sensor passes (exceeds) 0.
Each time, the comparison result is reversed. Therefore, in that case, automatic demagnetization will be performed when the direction of the earth's magnetism relative to the magnetic sensor changes from north to south, or from south to north. In this way, when the orientation of a moving object such as a ship or vehicle carrying electronic equipment is constant, demagnetization is not performed, and when the orientation of the moving object changes, the color C
It is possible to automatically demagnetize the RT direction each time it is affected by the earth's magnetic field. Therefore, manual operation is not required,
Moreover, wasteful power consumption is suppressed, and the frequency of disturbances in screen display is also reduced.

[0009]

DESCRIPTION OF THE PREFERRED EMBODIMENTS FIG. 1 is a block diagram showing the configuration of the main parts of an electronic device mounted on a mobile body, which is a first embodiment of the present invention. In FIG. 1, a magnetic sensor 1 includes, for example, a Hall element, detects the earth's magnetism and surrounding magnetism, and sends a detection signal a.
occurs. The amplifier circuit 2 amplifies the signal and outputs an amplified signal b. Comparison level generation circuit 3 provides comparison level c to comparator 4. A comparator 4 compares the level of the output signal b of the amplifier circuit 2 with a comparison level c and outputs a comparison result d. The trigger signal generation circuit 5 receives the output signal d of the comparator 4.
A trigger signal e is given to the degaussing circuit 6 when the signal is reversed. The trigger signal generation circuit 5 corresponds to the "degaussing instruction signal generation means" of the present invention. The degaussing circuit 6 includes a circuit for supplying attenuated alternating current to the degaussing coil 7, and supplies attenuated alternating current to the degaussing coil 7 every time the trigger signal e is applied. The demagnetizing coil 7 is provided on the color CRT 8 and demagnetizes the color CRT 8 by applying an attenuated alternating magnetic field to a predetermined location. The display device 9 provides various voltage and current signals to the color CRT 8 to display color images.

Next, FIG. 2 shows the waveforms of each part shown in FIG. 1. By changing the orientation of the magnetic sensor 1, the detection signal changes as shown by a in FIG. For example, when the magnetic sensor 1 faces north (magnetic direction), it generates a maximum positive voltage, and when it faces south, it generates a maximum negative voltage. When facing east or west, the output level of the magnetic sensor 1 becomes 0. If the level of the output signal b of the amplifier circuit 2 is equal to or higher than the comparison level c, the comparison result d of the comparator 4 becomes "H" level, and if the level of the output signal b of the amplifier circuit 2 is less than the comparison level c, the comparison result d becomes "H" level. The comparison result d of the device 4 becomes "L" level. The trigger signal generation circuit 5 generates a trigger signal e having a constant pulse width at the rising and falling timings of the comparison result d of the comparator 4. In response to the trigger signal e, the degaussing circuit 6 activates a circuit that supplies attenuated alternating current to the degaussing coil 7. As a result, a damped alternating current indicated by f is applied to the degaussing coil 7.

As described above, automatic demagnetization is performed each time the orientation of the magnetic sensor 1 changes from north to south or from south to north.

Next, FIG. 3 shows waveforms of the main parts of the electronic device mounted on a moving body according to the second embodiment.

In FIG. 3, the detection signal is a detection signal from a magnetic sensor amplified by an amplifier circuit which suppresses the amplification factor and reduces saturation. Further, c1 and c2 are two comparison levels given to the comparator. In this case, the comparator is c1-c
It acts as a window comparator with a window between the two comparison levels c1 and c2, and generates a trigger signal every time the detection signal exceeds the two comparison levels c1 and c2. This makes it possible to increase the frequency of automatic demagnetization in response to changes in the orientation of the moving body, and to obtain higher demagnetization effects.

Note that if a plurality of magnetic sensors are installed in different directions and the automatic degaussing circuit shown in the first or second embodiment is applied to the detection signal of each magnetic sensor, the direction of the moving object can be determined. Because changes are detected in detail,
A higher demagnetizing effect can be obtained.

[0015]

[Effects of the Invention] According to the present invention, manual activation of the degaussing circuit is not required, and degaussing is automatically performed only when the orientation of the CRT changes to the extent that color shift or uneven color may occur on the color CRT. As a result, unnecessary demagnetization is prevented, wasteful power consumption is suppressed, and screen display disturbances due to frequent automatic demagnetization are suppressed.

[Brief explanation of the drawing]

FIG. 1 is a block diagram of the main parts of an electronic device mounted on a mobile body according to a first embodiment.

FIG. 2 is a waveform diagram of each part in FIG. 1;

FIG. 3 is a waveform diagram of main parts of an electronic device mounted on a moving object according to a second embodiment.

[Explanation of symbols]

2-Amplification circuit 4- Comparator 7- Demagnetizing coil

Claims (1)

[Claims] Claims: 1. An electronic device mounted on a mobile body comprising a color CRT and a degaussing circuit for demagnetizing the color CRT,
a magnetic sensor that detects magnetism in the external environment; a level comparing means that compares the level of a detection signal from the magnetic sensor with a comparison level; and a demagnetizing instruction to the degaussing circuit every time the comparison result of the level comparing means is reversed. What is claimed is: 1. An electronic device mounted on a mobile body, comprising a degaussing instruction signal generating means for generating a signal.