JP2538317B2 - Electronic scales - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION (a) Field of Industrial Application The present invention relates to an electronic scale that converts the weight of an article into an electric signal and detects the detected weight electrically.

(B) Conventional technology Household scales are generally used for measuring cooking ingredients,
Cooking time is measured by using another cooking timer, and it is inconvenient to use these separate kitchen utensils because of problems such as installation location. In this regard, the cooking scale with a timer described in Japanese Utility Model Publication No. 52-96664 has a hole for attaching a timer on the front, side or top of an outer case formed of plastic or the like, and a timer with a bell inside thereof. I am wearing it so that I can set this timer from the outside, but since the bell rings only when the set time is reached, I have to quickly return to the kitchen when the bell rings, and after the bell rings the cooking time There was a problem that it was too long.

Further, in the case of weighing a plurality of items one after another, or when weighing the individual items, in the weighing device described in JP-A-60-173422, the input data level before loading is set to zero weight. Means for setting and storing, means for displaying the input data at the time of the first load by weight conversion, means for resetting the input data level at the time of the first load to zero weight, and means for the first load A means for displaying the input data of the second load by weight conversion when the second load is added, and a weight conversion of the first load and the second load at the same time with reference to zero weight before the first load. And a means for displaying the total weight, and a means for issuing an alarm when the total weight on the plate exceeds a preset weight or the maximum weight, regardless of the display, the timer described above. Similar to the above, when the alarm is issued, the measured weight has already been set. There is a problem that is beyond the amount.

Further, when a lithium battery is used as a primary battery in the power source of the electronic scale, the lithium battery has a larger internal resistance than a dry battery, and therefore the battery voltage drops when a relatively large current (about 10 mA) is passed through such as a buzzer. In addition, the value that decreases at this time gradually increases as the battery becomes exhausted. By the way, in the case of a scale with a buzzer, the current consumption is generally very small at about 150 μA during normal weighing, but it increases to about 10 mA when the buzzer sounds. For this reason, if the buzzer sounds when the battery is exhausted, the voltage that guarantees the circuit operation of the scale is temporarily dropped below but the weighing display becomes confused. Of course, the voltage obtained by adding the voltage drop when the buzzer sounds to the above guaranteed voltage is newly set as the operation guaranteed voltage for the circuit, and when the power supply voltage falls below that voltage, a low battery is displayed to inform the user of the battery replacement time. It is possible, but there was a problem that it was overlooked by just displaying.

(C) Problem to be Solved by the Invention The problem to be solved by the present invention is to eliminate the battery consumption of the power source before the battery runs out by using a set time or a set weight notification buzzer provided in the scale circuit. It is to inform.

(D) Means for Solving the Problem A counter for sampling the weight signal in accordance with a sampling period created by the microprocessor and counting the weight signal for each sampling is provided, and the count output of the counter is provided by the microprocessor. In an electronic scale that calculates and displays the obtained weight value on the display unit, the microprocessor, the counter, and the power supply unit connected to the display unit for supplying current and operated by the output from the microprocessor and A buzzer circuit supplied with a current from a power source section is provided, and a buzzer driving switching means for turning on and off according to a change in the output voltage of the power source section is connected in series with the buzzer constituting the buzzer circuit.

(E) Action There is a large difference between the current consumption when weighing and the current consumption when the buzzer sounds. When the buzzer sounds, the power supply voltage falls below the circuit guarantee voltage, but when the buzzer does not sound, it is above the circuit guarantee voltage. Is always present. With this in mind, the buzzer will stop ringing when it detects a voltage below the circuit guarantee voltage only after the buzzer rings. In this way, the user knows that the buzzer will always disappear before the battery is exhausted and weighing cannot be performed, and the battery will soon run out.

(F) Example Hereinafter, the electronic balance of the present invention will be described in detail with reference to the examples of the drawings. Figure 2 shows the basic block circuit. In the figure, (1) is a weight-capacitance conversion circuit configured by a parallel plate capacitor which is displaced against the elastic force of the leaf spring due to the weight of the weighing object, and (2) is a time constant circuit including the above capacitor. A capacitance-frequency conversion circuit that detects a change in capacitance due to displacement of the capacitor as a change in oscillation frequency of the oscillation circuit, and (3) outputs a sampling pulse having a constant width to an output terminal (SP (4) outputs the AND of the sampling output signal and the output signal of the capacitance-frequency conversion circuit (2) via the AND circuit (5).
A counter that inputs the output of the D circuit (5) and counts the number of pulses, and (6) is a display output terminal (D
A liquid crystal display unit which is connected to P) and digitally displays the weight of the object to be weighed based on the weight display output of the microcomputer (3). The counter (4) counts the number of pulses of the pulse signal of the capacitance-frequency conversion circuit (2) that passes through the AND circuit (5) while the microprocessor (3) outputs the sampling pulse. Then, the count value is input to the microprocessor (3) as a weight data signal.

Normal weighing operation is possible with the above circuit configuration. That is, the weight of the object (not shown) placed on the weighing pan (not shown) is converted into the capacitance of the capacitor by the weight-capacitance conversion circuit (2), and the capacitance- The change of the capacitor capacity is output from the frequency converter circuit (2) as the change of the oscillation frequency by the oscillator circuit of the frequency converter circuit (2) having the capacitor capacity as a time constant. On the other hand, a sampling pulse having a constant width is output from the output terminal (SP) of the microprocessor (3) by the built-in clock circuit, and the output signal of the output terminal (SP) is the output of the frequency conversion circuit (2). It is input together with the AND circuit (5), and both are logically operated (AND operation) here.
The output of the AND circuit (5) is input to the counter (4). The counter (4) counts the output pulse of the frequency conversion circuit (2) passing through the AND circuit (5) while the microprocessor (3) outputs the sampling pulse, and the counted value To the microprocessor (3).

The microprocessor (3) reads the above pulse count value, and when the weight is Og (only the weighing pan), the pulse number and Xg
The number of pulses of time (weighing pan + object to be weighed) is calculated, and the calculation result is converted into weight and output to the liquid crystal display section (6) through the output terminal (DP), and the liquid crystal display section (6) is displayed. Displays the weight of the object to be weighed.

By the way, (7) is a key matrix circuit comprising a timer mode setting key and a timer time setting key for operating a timer circuit section built in the microprocessor (3), and (8) is the key matrix. Circuit (7)
Is a buzzer circuit including a buzzer (BZ1) which is driven by an alarm signal output from an alarm output terminal (BU) of the microcomputer (3) when the time set by the above has passed. Further, (9) is a power supply for supplying operating currents to the capacitance-frequency conversion circuit (2), counter (4), microprocessor (3) liquid crystal display (6) and buzzer circuit (8), respectively. And preferably a lithium battery is used.

As shown in FIG. 1, the buzzer circuit (8) is a transistor (TR2) (emitter grounded type) in which the alarm output terminal (BU) of the microprocessor (3) is connected to the base via the resistor (R3). And a buzzer (BZ1) and a diode (D1) consisting of a voltage element connected in series with this, an excitation coil (L1) connected to both ends of the buzzer (BZ1), and a buzzer (BZ1) connected in series Transistor (TR
1) and the base terminal of the transistor (TR1) with a resistor (R
2) is connected to the power supply voltage detection circuit (IC1) via an input terminal of the power supply voltage detection circuit (IC1) is connected to the power supply section (9), and the collector of the transistor (TR1). The terminal is connected to the power source section (9) through a resistor (R1). The timer time setting key of the key matrix circuit (7) has a key for setting a digit of 10 minutes and a key for setting a digit of 1 minute.

While the transistor (TR1) is in the conductive state while the output of the power supply section (9) is sufficiently obtained, the operation method of the alarm means at this time will be described. First, the timer mode setting key is pressed to make the built-in circuit of the electronic scale timer. And the weighing operation of the scale is interrupted.

Then, a key for setting a timer time is operated to set a time from 0 to 99 minutes. Next, when the timer mode setting key is pressed again, the timer circuit in the microprocessor (3) starts operating. The reference time of this timer circuit is the original oscillation circuit composed of the crystal oscillator in the clock circuit of the microprocessor (3).

The alarm output of the microprocessor (3) is output from the alarm output terminal (BU) twice by the arithmetic circuit in the microprocessor (3) 10 seconds before the set time and the set time. Is programmed. set time
The alarm output 10 seconds before is a single pulse of 2048Hz or 4096Hz followed by a predetermined interval, and the second alarm output is a pair of pulses of small intervals of 2048Hz or 4096Hz followed by a predetermined interval. It is a thing. Therefore, the buzzer circuit (8) outputs an alarm sound of "beep ... beep" 10 seconds before the timer setting time and "beep ... beep" when the remaining time is 0 seconds.

On the other hand, the key matrix circuit (7) can be used as follows. That is, the key matrix circuit (7) is provided with a preset mode key, a 100 g digit key and a 10 g digit key for setting the required weight in advance. In this way, first, the preset key is pressed to interrupt the operation of the electronic scale, and the built-in circuit is set to the preset mode.
At this time, the digit of 1 g of the set weight is always set to 0. Therefore, the set weight can be set in the range of 10 to 990g in steps of 10g. Then, by pressing the preset mode key again, the set numerical value is stored in the memory of the microprocessor (3), and the reference value of the warning sound immediately before reaching the set weight is calculated in the microprocessor (3).

 The standard value of the warning sound is when the set weight is 50g or more ... Set weight x 90% When the set weight is less than 50g ... Set weight-5g.

Calculate the reference value of the warning sound, and use the microprocessor (3).
When it is stored in the memory of, the normal weighing mode of the electronic scale is returned.

When the set weight is 50g or more, the accuracy may be a little rough, so set weight> measured weight ≥ set weight x 90% Also, when the set weight is 50g or less, it is necessary to increase the accuracy set weight> measured weight ≥ The microprocessor (3) outputs an alarm to the buzzer circuit (8) so that the first alarm signal is generated when the set weight is −5 g and the second alarm signal is generated when the set weight ≦ measured weight. To supply.

The set weight data and the reference value of the warning sound do not disappear unless the microprocessor (3) is reset (for example, the power is turned off), so that the same weight can be repeatedly weighed.

By the way, while the output of the power supply section (9) is sufficient, the output terminal (OUT) of the power supply voltage detection circuit (IC1) is at "High" level, and the transistor (TR1) is always in a conductive state. 3) Alarm output terminal (BU)
If the transistor (TR2) is turned on by the output of, it will conduct immediately.

On the other hand, if the buzzer signal is output from the microprocessor (3) when the power supply voltage has dropped due to the consumption of the lithium battery in the power supply section (9), a buzzer current will flow to the buzzer circuit (8) and the power supply voltage will drop further. To do. However, when the power supply voltage drops below the voltage obtained by adding the voltage of the circuit that can guarantee the metering operation to the lowered voltage, the power supply voltage detection circuit (IC1) detects this voltage and the output becomes the "Low" level. Therefore, the transistor (TR1) is turned off, the current in the buzzer circuit (8) disappears, and the power supply voltage rises again by the voltage drop of the buzzer circuit (8). At this time, the power supply voltage is higher than the circuit voltage that can guarantee the metering operation, and the metering can be performed normally. Then, since the buzzer drive current no longer flows to the buzzer circuit (8), the user can know when to replace the battery of the power supply unit because the buzzer (BZ1) does not ring.

(G) Effect of the Invention As described above, the present invention is provided with the counter that samples the weight signal in accordance with the sampling period created by the microprocessor and counts the weight signal for each sampling.
In an electronic balance that calculates the count output of the counter by the microprocessor and displays the obtained weight value on the display unit, a power supply unit that is connected to the microprocessor, the counter, and the display unit, and supplies a current. A buzzer circuit that operates by the output from the microprocessor and is supplied with a current from the power supply unit is provided, and a buzzer driving switch that turns on and off according to a change in the output voltage of the power supply unit in series with the buzzer forming the buzzer circuit. Since the means is connected, it is possible to prevent the weighing display from coming due to a drop in the power supply voltage due to the buzzer current, and also to give the effect of notifying the replacement time of the battery constituting the power supply unit by the presence or absence of the buzzer sound.

[Brief description of drawings]

FIG. 1 is a main circuit diagram showing the configuration of a buzzer circuit of the electronic scale of the present invention, and FIG. 2 is a block circuit diagram showing the circuit configuration of the electronic scale. (3) …… Microprocessor, (4) …… Counter,
(6) …… Liquid crystal display, (9) …… Power supply, (8) ……
Buzzer circuit, (BZ1) …… Buzzer, (TR1) …… Switching means.

Claims (1)

(57) [Claims] 1. A counter for sampling a weight signal in accordance with a sampling period created by a microprocessor and counting the weight signal for each sampling, the count output of the counter being calculated by the microprocessor,
In the electronic scale that displays the obtained weight value on the display unit, the microprocessor, the counter and the power supply unit connected to the display unit for supplying an electric current and operated by the output from the microprocessor and the power supply unit. An electronic scale comprising: a buzzer circuit to which a current is supplied, and a buzzer driving switching means which is turned on / off according to a change in the output voltage of the power supply unit in series with the buzzer constituting the buzzer circuit.