JPS6263378A - Portable data collecting device - Google Patents

Abstract

PURPOSE:To use a smaller button type battery, etc., by reducing the contrast and prolonging the life of the battery of a portable data collecting device. CONSTITUTION:A CPU 1 controls a RAM 3, an interface LSI 4 and a display driving circuit 5 by a program written at a ROM 2. The CPU 1 always stops a clock, only when the key input is executed, oscillates the clock and inputs the data. The data accumulated in such a way are transferred through the interface LSI 4 to a data repeater. Until the transfer is completed, a part or whole parts of the data, the message, etc., are displayed, and after the data transfer is completed, the contrast is reduced, and thereby, displaying is extinguished and the CPU 1 is stopped.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] This invention relates to a portable data collection device powered by a battery.

[Conventional technology]

Conventionally, in devices equipped with one display device, once the contrast of two displays is set, the same contrast is always used unless the setting is changed.

[Problem that the invention seeks to solve]

However, in the conventional method, a certain amount of drive current flows through the segment so that the contrast does not change even after the transfer is completed. Therefore, it is difficult to reduce the current consumption, and there is a drawback that the battery life of the portable data collector is shortened.

SUMMARY OF THE INVENTION It is therefore an object of the present invention to overcome these disadvantages of the conventional techniques and extend the battery life of portable data collectors.

[Comparative means to solve problems]

To solve the above-mentioned problems, the present invention has a portable data collection device that transfers the collected data after it is finished.

When no characters are displayed on the multi-dot matrix liquid crystal display panel, in order to reduce current consumption, the amplitude of the driving AC voltage is lowered to lower the contrast. ] Generally, a liquid crystal display element is equivalently replaced with a capacitor, and lowering the contrast means lowering the amplitude of the AC voltage driving the liquid crystal display element. That is, this means that the AC voltage applied to the capacitor is reduced, and the current flowing to the liquid crystal display element is also reduced. Therefore, current consumption can be reduced.

[Real example]

Embodiments of the present invention will be described below based on the drawings.

In FIG. 1, j9. RAM3-interface LSI4. and controls the display drive circuit 5. Maf
4 CPU 1 operates by constantly stopping the clock and oscillating the clock only when available, and inputs data. The data thus viewed is transferred to a data relay (not shown) via interface I, 8I4. Until the transfer is completed, part or all of the data, messages, etc. are displayed, but as the data transfer is completed, the display is erased by lowering the contrast, and 0PU1 stops.

The display drive circuit 5 includes a common signal generation circuit 6 and a segment signal generation circuit 7, and generates signals necessary for one display to display characters, symbols, etc. on the multi-character dot matrix liquid crystal display board 8. The display contents are managed by the CPU 1 only when they are changed.

It is stored as data in the common signal generation circuit 6.

Next, the first display drive circuit 5 will be explained in detail with reference to FIG. The common signal generation circuit 6 includes a display RAM, a character ROM, etc. (both not shown), and has a C! PU1 is an address bus and a data bus.

It is connected to other signal lines. (When a signal is sent from the 3PU 1 in the form of an ASCII code, etc., it is converted into character pattern data, latched, and further transmitted to the segment signal generation circuit 7, which generates a common signal and displays it on a multi-character dot matrix liquid crystal display. Board 8
I am telling you. The segment signal generating circuit 7 generates the next segment signal corresponding to 80 dots on the multi-character dot matrix liquid crystal display board, which is generated based on the character pattern data from the common signal generating circuit 6. In addition.

The contrast shading is achieved by the fact that the common signal generating circuit 6 changes the peak values of the common signal and the segment signal by using a booster circuit.

The WJ3 diagram is included in the common signal generation circuit 6, and 64
It is a figure showing a pressure circuit. The gate control circuit 9 uses contrast information from the address bus and data bus.
works. The dividing resistor 1o is driven by a constant current, and
The potential of the arbitrary connection point is set by the gate control circuit 9
Analog switch controlled by 11. It can be machined into the voltage follower 12 and taken out.

FIG. 4 is an example of each common signal and segment signal.

The common signal has 4 levels, and the segment signal has 3 levels of peak value, and the difference between the signals is such that the level does not light up at level 4, but it lights up at level 4.

Generally, liquid crystal display elements are thought of as capacitors.

When an alternating current voltage is applied, a through current flows depending on the amplitude and frequency. A certain amount of alternating current voltage is always applied to the unlit segment, and the polarity of the signal changes, causing a through current to flow even at 9 o'clock. The current consumed when 0PU1 is stopped is between interface L8 and 4.

These are the circuit current of the display drive circuit 5 and the through current flowing through this liquid crystal display element. Since the multi-character dot matrix liquid crystal display panel 8 can be considered as a large number of capacitors, a large amount of current is required for one display. Next, let us consider the case where the contrast is lowered. As the output of the booster circuit decreases, the peak values of the common signal and segment signal also decrease, which in turn reduces the AC amplitude voltage applied to the liquid crystal display element and reduces the through current. This lowers the contrast and is the original state. Please note that in order to prevent liquid crystal deterioration, it is not possible to apply DC voltage to the liquid crystal display element.

The operating time of CPU1 is very short, and the average current is C
It is quite small compared to when the PUI is stopped. Therefore, as mentioned above fc, suppressing the current consumption when the C'PU is stopped is the key to the battery system.

Here, the difference in battery S life between the conventional method and the present invention will be calculated based on an actual example.

(1) The time from the start of data input to the end of transfer is one hour.

(2) The current consumption when the CPU is operating is 1.2 mA, but in a portable data collector with low current consumption, the CPU is almost in a stopped state.

(3) The current consumption when the CPU is stopped is 20 μA when the contrast is highest and 4071Δ-fi is low.

(4) Assuming that the CPU operates for 100 seconds a day, the average current consumption will be as follows.

Conventional method 100 seconds x 1.2 mA 786400 seconds + 40 / J A
==41.39μA This method 100 seconds x 1.2mA 786400 seconds 122 561
μA (5) The battery life when using a 120mAh battery is as follows.

〔Effect of the invention〕

As explained above, this invention can extend the battery life of a portable data collection device by reducing the contrast, so it is possible to use small button-type batteries, etc. In addition to being able to meet the demands of being thin and thin, the number of troublesome battery replacements can be reduced, and running costs can be kept low.

[Brief explanation of the drawing]

Figures 1 and 2 are block diagrams of the portable data collector and 9 display drive circuit of the present invention, Figure 3 is a circuit diagram of the common signal generation circuit, and Figure 4 is a waveform diagram of the common signal and segment signal. be. 5...Display drive circuit 6...Common signal generation circuit 7...Segment signal generation circuit 6...Multi-character dot matrix liquid crystal display board 9...
More than gate control circuit

Claims (2)

[Claims] (1) In a portable data collection machine that uses a battery as a driving power source and a multi-character dot matrix liquid crystal display board as a display part, the portable data collection machine A portable data collection device characterized by reducing the contrast of a character dot matrix liquid crystal display board. (2) The portable data collection device according to claim 1, wherein the contrast is lowered by lowering the amplitude of the AC voltage driving the multi-character dot matrix.