JPS6151526A - Load cell balance - Google Patents

Abstract

PURPOSE:To reduce power consumption greatly by performing ON.OFF control over a driving voltage supplied to the load cell synchronously and intermittently during the operation of an A/D converter. CONSTITUTION:The circuit of the load cell balance consists of the load cell 1, power source 2 for applying the driving voltage VE, filter 4, A/D converter 5, reference voltage generating circuit 6, microcomputer system 10, photocoupler 12 having a phototransistor 12 and a photodiode 13, etc. Further, the supply of the driving voltage VE to the load cell 1 is brought under ON.OFF control through the operation of the diode 13 controlled with a signal SC from the microcomputer 10. Then the diode 13 is so controlled that the driving voltage VE is supplied to the load cell 1 only for 210msec after an STC signal is applied to the A/D converter 5, thereby reducing the power consumption of the load cell 1 to half.

Description

[Detailed description of the invention] Technical field of invention The present invention relates to a load cell scale.

Technical background of the invention and its problems In recent years, in various electronic devices, the development of LSI and CIt/10
Due to the spread of SIC, advances in semiconductor technology, etc., power consumption is becoming lower, and it is desired that load cell scales be driven by batteries due to lower voltage consumption. Therefore, when looking at the main counterfeit electrical part of the load cell scale, the load cell part, A
/D conversion section, logic (CI"U) section, 1 display section, etc. Due to recent advances in semiconductors, the OP amplifier of the A/D conversion section is a low power consumption IC, and the A/D converter is 0MO5I.
C. The logic section uses a 0MO5 1-chip microcomputer, and the display section uses a liquid crystal, etc., resulting in considerably low power consumption [
You can aim for Therefore, in a load cell scale, the load cell section consumes a large amount of power. This load cell section is generally configured by bridge-connecting strain gauges (resistors), and it is possible to reduce power consumption by increasing the resistance value of the resistors and reducing the current. However, if the resistance is too high, the configuration of the OP amplifier provided at the next stage will become complicated.

Furthermore, as shown in FIG. 8, there is also a device that focuses on key operations to reduce the power consumption of the load cell section. That is,
When a key input such as a numeric keypad is made to input a unit price, drive voltage is supplied to the load cell and the A/D converter is operated to enable weighing operation. When it continues for a long time, it is determined that the scale is not in use, and the supply of drive voltage to the load cell is turned off. At this time.

A message indicating that the device is on standby or the like is displayed on the display.

When the unit price is entered using a numeric keypad or the like, it is determined that the scale has been used again, and a drive voltage is supplied to the load cell to enable weighing operation. According to this, it is possible to roughly reduce power consumption, but
Output from the load cell is not always required when a key is input;
This is insufficient for reducing power consumption.

OBJECTS OF THE INVENTION The present invention has been made in view of the above points, and an object of the present invention is to provide a load cell scale that can significantly reduce power consumption in the load cell section.

Summary of the Invention The present invention focuses on the fact that an output voltage from a load cell is required when an A/D converter operates, and intermittently turns on the drive voltage supplied to the load cell in synchronization with the operation of the A/D converter. -Or''F control, the power consumption of the load cell can be significantly reduced.

Embodiment of the Invention A first embodiment of the present invention will be described based on FIG. First, a drive voltage VE is applied by a power source 2 between the input terminals of a load cell 1 in which four resistors are bridge-connected. The output voltage V taken out between the output terminals of the load cell 1 is inputted to the A/D converter 5 as an input voltage Vin via an OP amplifier 3 and a filter 4. Here, the filter 4 is a low-pass filter that removes the alternating current component of the output voltage VL due to external vibrations and converts it into an input voltage Vin containing only the direct current component. Further, a reference voltage generation circuit 6 is provided that generates a reference voltage vref based on the voltage VE driven by the power supply 2.

This reference voltage generation circuit 6 is composed of a plurality of comparators and the like, and the reference voltage Vref is inputted to the A/D converter 5. This A/D converter 5 is driven by an A/D converter power source 7 that is separate from the power source 2, and its digital output is input to a microcomputer system 10 to which a keyboard circuit 81 and display 9 are connected. has been done. Further, the A/D converter 5 specifically uses an ICL7135 manufactured by Intersil Corporation, and is operated by applying a start signal STC from the microcomputer system 10.

A phototransistor 12 of a photocoupler 11 is interposed between the load cell power supply 2, and the drive voltage V to the load cell 1 is adjusted based on the operation of the photodiode 13.
It is configured so that the supply of E can be turned on and off.

This photodiode 13 is controlled by a power control signal SC from the microcomputer system 10.

In such a configuration, A/D by tcL7135
By applying the start signal STC (from L level to H level) as shown in FIG. 2(a), the converter 5 converts from O1-Zero to the first integral in the integration time as shown in FIG. 2(b).
Tx = 200m80c operates until the third integration, and then the strobe signal is l + 5sec x 5 pulses (T 2 =
5 m5ec), and data will be output in synchronization with this signal. However, in this embodiment, we focused on the operation of such A/D converter 5, and taking a margin,
After the start signal STC is output, load cell 1 receives 210
The photocoupler 11 is controlled to supply the drive voltage vE only for about yasec. As shown in FIG. 2(d), Ton=Toff=2 L O
If the duty is 1/2, which is +m5ac, the power consumption of the load cell I will be 1/2. Moreover, as shown in the same figure (e), Ton=210 wrscc, Toff=42
When the duty is set to 1/3 (0 m5ec), the power consumption of the load cell 1 can be reduced to 173.

Note that this embodiment is also based on the control shown in FIG. 8, and the load cell 1 and the load cell 1! J.J.
m, pressure V E (7) Intermittent ON/OFF control of supply is performed as control during "normal operation" in FIG.

Next, FIG. 3 shows a modified example, in which TC5092 manufactured by Toshiba is specifically used as the A/D converter 5. 14 is a buffer.

The A/D converter 5 is based on this TC5092.

As shown in Figure 4(a), start signal STC is applied for 3 μs.
By giving more than ec, an integral operation is performed.

55a+sec is required as integration time T3 (see figure (
b)) After that, EOC is output to inform the microcomputer system 10 of the end of A/D conversion. At this time, 6 rssacs are required as T3 to read the data. Therefore, please make sure that there is enough time before issuing the STC signal.
From the time of rasec, the drive voltage VE is supplied to the load cell 1 by 65a+aec and then turned off. When this is done as shown in FIG. 4(d), the power consumption of the load cell l becomes l/2.

Also, as shown in the same figure (e), Ton = 65m5ec, T
When the duty is set to 1/3 (off = 130 ssec), the power consumption of the load cell 1 can be reduced to 173.

Next, a second embodiment of the present invention will be described with reference to FIGS. 5 and 6. In this embodiment, TC5092 manufactured by Toshiba is specifically used as the Δ/D converter 5, which is a multi-input type.

First, the output voltage from the load cell 1 is determined by the amplifier circuit 15.
15 to Vinl of the A/D converter 5. Further, the drive voltage VE for the load cell 1 is taken out and input to Vi and nz of the A/D converter 5. Furthermore, in this embodiment, the drive voltage VE is applied to the load cell 1.
The power supply 2 that applies the voltage is also shared by the A/D converter 5. Therefore, as in the above embodiment, the photocoupler 11
The transistor 16 is interposed between the load cell power supplies 2, so that there is no need to separate them using a .

In such a power supply sharing method, the reference voltage Vref
cannot be taken out independently, the drive voltage VE applied to the load cell I and the output voltage VL of the load cell 1 are successively compared to provide ratiometric digital processing. To explain based on FIG. 6, first, the immediate J voltage VE
Start to detect (H%5TCI is output. At this time, Vinz can be input to the A/D converter 5 (there is a 1 selection terminal, not shown, and this is controlled by the microcomputer). Therefore, When EOCI is output, the data of the drive voltage VE for the load cell 1 is taken into the microcomputer system 10.
- When the signal 5TC2 is output, the A/D converter 5 is switched to enable the input of Vinx and detects the output voltage Vt of the load cell 1. When the EOC2 is output, this output voltage Vt is detected. The microcomputer system 1G takes in the data of the reference voltage Vre.
Since f is 5V and 8191 counts, yiA and J power V
If the data based on E is a count, and the data based on output voltage Vt is b count, then the corrected data, X count, is given by the microcomputer system l,
There is one thing to be done in 10. In this way, accurate weight data that is not affected by fluctuations in the drive voltage VE can be obtained with a simple circuit configuration that shares a power source.

FIG. 6(d) shows the supply of the driving voltage VE to the load cell 1, and the voltage is set to -Ton=130m5ec, which is slightly longer than the TS from 5TC1 to EOC2. In this case too, if the duty is 1/2, Ton=
Toff = 130 tasec, duty 1/
3 to 9 Ton = 130 m5ec, Toff
= 260m5ec.

Next, a third embodiment of the present invention will be explained with reference to FIG.

This embodiment is a shared power supply type like the second embodiment, but since the A/D converter 5 is a single input type, the drive voltage VE and output voltage of the load cell 1 are controlled by an analog switch. 17. Vin of A/D converter 5 via 18
6 analog switches 17.18
is an N dynamic voltage input control signal 5DC1 output voltage input control (controlled by n soc from the microcomputer system 10, and selectively inputs the drive voltage VE and output voltage Vt to the A/D converter 5. Yes.Others are
This is similar to the second embodiment, and corrected weight data is obtained.

Effects of the Invention As mentioned above, since the output voltage from the load cell is required during the operation of the A/D converter,
Since the drive voltage supplied to the load cell is intermittently controlled ON/OFF in synchronization with the operation of the converter, it is possible to significantly reduce the power consumption in the load cell section and achieve low power consumption. If the A/D converter is of a shared power supply type, data based on the drive voltage of the load cell and data based on the output voltage are compared to obtain corrected weight data.

Accurate data that is not affected by fluctuations in drive voltage can be obtained.

[Brief explanation of the drawing]

FIG. 1 is a circuit diagram showing a first embodiment of the present invention. FIG. 2 is a timing chart showing its operation, FIG. 3 is a circuit diagram showing a modified example, FIG. 4 is a timing chart showing its operation, and FIG. 5 is a circuit diagram showing a second embodiment of the present invention. Figure 6 is a timing chart showing the operation, Figure 7 is a timing chart showing the operation.
The figure is a circuit diagram showing a third embodiment of the present invention, and FIG. 8 is a flowchart showing a conventional system. l...Load cell, 2...Power supply, 5...A/D converter, 6...Reference voltage generation circuit, 17-18...
・Analog switch

Claims (1)

[Claims] 1. A load cell scale that obtains weight data by converting the output voltage from a load cell into a digital signal using an A/D converter, which performs weighing operation by supplying a driving voltage to the load cell based on key input. When the display state of 0g display continues for a predetermined time or more, the supply of drive voltage to the load cell is turned off until the key is input again, and the drive voltage is supplied to the load cell based on the key input. A load cell scale, characterized in that the A/D converter is intermittently ON/OFF controlled in synchronization with the operation of the A/D converter. 2. A load cell scale that obtains weight data by converting the output voltage from the load cell into a digital signal using an A/D converter, which supplies driving voltage to the load cell based on key input to enable weighing operation and display 0 g. When the display state continues for a predetermined period of time or more, the supply of drive voltage to the load cell is turned off until the key is input again, and the drive voltage is applied to the load cell separately from the power supply for the A/D converter. Based on this drive voltage, a reference voltage generation circuit generates a reference voltage, and the output voltage from the load cell is input to the A/D converter along with this reference voltage, and the A/D converter converts it into a digital signal. 1. A load cell scale, characterized in that the drive voltage supplied to the load cell is intermittently ON/OFF controlled in synchronization with the operation of the A/D converter based on a key input. 3. A load cell scale that obtains weight data by converting the output voltage from the load cell into a digital signal using an A/D converter, which supplies driving voltage to the load cell based on key input to enable weighing operation and display 0 g. When the display state continues for a predetermined period of time or more, the supply of drive voltage to the load cell is turned off until a key is input again, and the A/D converter is of a multi-input type, and the A/D converter is of a multi-input type. The drive voltage applied to the load cell and the output voltage from the load cell are input to separate input positions of the A/D converter, and the drive voltage converted into a digital signal by the A/D converter is The data based on the voltage and the data based on the output voltage are compared to obtain corrected weight data, and the drive voltage supplied to the load cell is synchronized with the operation of the A/D converter based on key input, and the data is intermittently A load cell scale characterized by automatic ON/OFF control. 4. A load cell scale that obtains weight data by converting the output voltage from the load cell into a digital signal using an A/D converter, which supplies driving voltage to the load cell based on key input to enable weighing operation and display 0 g. When the display state continues for a predetermined period of time or more, the supply of drive voltage to the load cell is turned off until the key is input again, and the A/D converter is of a single input type, and the A/D converter is of a single input type. The drive voltage applied to the load cell and the output voltage from the load cell are selectively input to the same input position of the A/D converter via an analog switch, and the A/D converter shares a power source with the A/D converter. The data based on the drive voltage converted into a digital signal by the converter is compared with the data based on the output voltage to obtain corrected weight data, and the drive voltage supplied to the load cell is adjusted based on the key input. A load cell scale characterized by intermittent ON/OFF control in synchronization with the operation of a D converter.