JPH024214A - Handy terminal - Google Patents

Abstract

PURPOSE:To simplify the adjustment of contrast, and also, to eliminate a contact abrasion and a contact failure of a switch and a variable resistor by controlling the contrast of a liquid crystal display part in accordance with a power supply voltage and the temperature of use environment. CONSTITUTION:A main control part 1 calculates optimum data of contrast, transfers it to an I/O 15, and it is outputted to a D/A converter 14 from an output port of the I/O 15. The D/A converter 14 converts a digital signal to an analog signal and it is outputted to a liquid crystal driving circuit 11, and the contrast of the liquid crystal part is adjusted. In such a way, since the handy terminal body is provided with an automatic adjusting function of the contrast of the liquid crystal part, a switch and a volume are eliminated, and a fault to be caused by a contact failure is not generated. Also, such troublesomeness as an operator adjust the contrast each time due to the variation of voltage/temperature is eliminated.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a handy terminal having a main control section and various I/O sections.

[Conventional technology]

Conventionally, in this type of handy terminal, the contrast of the liquid crystal display was adjusted by operating a switch or varying the voltage using a volume control, using an operator's operation.

[Problem to be solved by the invention]

As mentioned above, in conventional handy terminals, the contrast is adjusted by varying the voltage using a switch or a volume.

However, the contrast of liquid crystals is greatly affected by voltage and temperature. The higher the voltage, the darker the contrast; the lower the voltage, the lighter the contrast. Also, depending on the temperature, it becomes thicker in high places and thinner in cold places. Handy terminals in particular use dry batteries or NiCd batteries, so the initial voltage is high and the voltage fluctuates rapidly depending on the load used. In addition, the temperature of the place where it is used is 40
°C to 0°C, or sometimes below 0°C because it is used in a freezer.

Therefore, the operator is burdened with having to adjust the contrast each time the voltage/temperature changes. Also, since adjusting the contrast is complicated,
Switch and volume contacts become worn, causing contact failure.

[Means to solve the problem]

According to the present invention, in a handy terminal having a main control section, various I/O sections, and a liquid crystal display section, it is possible to control the contrast of the liquid crystal display section according to the power supply voltage and the temperature of the usage environment. You can get a handy terminal with special features.

〔Example〕

Next, the present invention will be described in detail with reference to the drawings showing one embodiment of the present invention.

Referring to FIG. 1, one embodiment of the present invention has a main control section 1, a RAM 2, and an interface circuit 3, as in the prior art.
1, a mechanical device 4, a ROM 5, an output device 6, and a liquid crystal 8. Furthermore, this embodiment has a liquid crystal contrast automatic adjustment section 7.

In the liquid crystal contrast automatic adjustment section 7, as shown in FIG. 2, a voltage detection circuit constantly monitors the drive power supply voltage of the handy terminal and outputs the voltage level as an analog signal. The output analog signal is converted into a digital signal by the A/D converter 12 and input to the l/O 15. Similarly, the temperature detection circuit/O outputs the sensed temperature state as an analog signal. The output analog signal is converted into a digital signal by the A/D converter 13 and input to the l/O 15. The two input data are transferred from the l/O 15 to the main control section 1 and analyzed.

The main control unit 1 calculates optimal contrast data,
It is transferred to l/O 15 and output from the output port to D/A converter 14 (l/O 15<7).

The D/A converter 14 converts the digital signal into an analog signal and outputs it to the liquid crystal drive circuit 11 to adjust the contrast of the liquid crystal section.

〔Effect of the invention〕

As described above, according to the present invention, since the handy terminal main body has an automatic adjustment function for the contrast of the liquid crystal section, there is no need for a switch or a volume control, and troubles due to contact failures do not occur. Furthermore, the operator no longer has to worry about adjusting the contrast each time the voltage/temperature changes.

[Brief explanation of the drawing]

FIG. 1 is a block diagram of a handy terminal according to an embodiment of the present invention, and FIG. 2 is a block diagram of an automatic liquid crystal contrast adjustment section in the embodiment shown in FIG. 1: Main control unit, 2-RAM, 3: Interface circuit, 4: Mechanical equipment, 5: ROM, 6: Output equipment, 7:
Liquid crystal contrast automatic adjustment section, 8: Liquid crystal, 9: Voltage detection circuit, /O: Temperature detection circuit, 11: Liquid crystal drive circuit, 12
: A/D converter, 13: A/D converter, 14: D/A converter, 15: Ilo. Agent Patent Attorney Susumu Uchihara

Claims (1)

[Claims] What is claimed is: 1. A handy terminal having a main control section, various I/O sections, and a liquid crystal display section, wherein the contrast of the liquid crystal display section is controlled according to the power supply voltage and the temperature of the environment in which it is used.