JPH0224519A - Power source circuit of electronic scale - Google Patents

Abstract

PURPOSE:To make it possible to perform power supply operation in a relatively dark place by providing first and second switching means between a load circuit and a solar battery and an auxiliary battery, and controlling the switching means with the voltage of the solar battery. CONSTITUTION:A first switching means TR1 is connected between a basic circuit MC of a scale which is to become a load and a solar battery BT1. A second switching means TR1 is connected between the circuit MC and a lithium battery BT2 which is an auxiliary battery. A control switching means TR4 is connected to the base circuits of these switching means. The control switching means T4 undergoes ON/OFF control with the output voltage of said solar battery BT1. In this way, the solar battery BT1 can supply the power source even if the output voltage is low when the voltage of the solar battery BT1 becomes the value at which the switching means TR4 is turned ON and OFF. Therefore, the scale can be used even with lighting in a kitchen and the like where the illumination is low.

Description

DETAILED DESCRIPTION OF THE INVENTION Field of Industrial Application The present invention relates to an electronic balance using a solar cell as a power source, and to the configuration of a power supply circuit including the solar cell.

(b) Conventional technology For example, in an electronic scale that measures and displays the weight of an object to be weighed, there is provided a vibrating weight sensor for detecting the weight of the object to be weighed, and the vibrating type An electronic scale equipped with a liquid crystal display device that displays the weight detected by a weight sensor and powered by a solar battery has been disclosed. Since this was impossible, Hondesen developed a method for rounding up stored data by connecting a solar battery and a primary lithium battery for memory backup in parallel to the basic balance circuit, as shown in Figure 3, and supplying power from both. proposed to supply it.

That is, in Fig. 3, the negative terminal of the solar cell (BTI) and the negative terminal of the lithium battery (BT2) are connected to form a common ground (GND), and the positive terminal of the thick battery (BTI) is connected to prevent backflow. Connected to the emitter terminal of the transistor ('rttr) via a diode (Dl), connected the positive terminal of the lithium battery (BT2') to the emitter terminal of the transistor (TR2), and both the transistors (rRl) (Ta2). Connect the collector terminal of the resistor (R4)
are connected to each other through a voltage stabilizing circuit to serve as output terminals to the scale basic circuit (MC), and each of the pace terminals of the transistors (TRI) (TR2) is connected to a transistor (MC) through a pace resistor (R2M17). A short resistor (R7) is inserted between the pace terminal of the transistor (TR3) and the ground (GNI)'1 via a pace resistor (R6), and the pace resistor (R6) is connected to the collector terminal of the transistor (TR3). is the analog switch IFKT (TR
a) is connected to the pre-fertility scale basic circuit (MC). And the gate of IF E T (TR4)! terminal O)
#i is connected to the positive terminal 1 of the solar cell (BTI) via a low resistance R1) and to the ground CGHD) via a resistor (R2), and the drain terminal (to) is connected to the switch (FNs). The lithium battery (BT2
) is connected to the positive terminal of the The drawback of this circuit is that unless the voltage of the solar cell CB1) is relatively high, power cannot be supplied to the scale basic circuit (MC). That is, in order to close the switch (8Wl) and supply power to the scale basic circuit (MC), the transistor (TR3) and IFIli are connected.
T (TR4) must be conductive, but for this the gate voltage of FIT (TR4) must be FI! iT (T
R4) must be greater than or equal to the sum of the voltage between source c and gate (about 17) and the emitter-collector voltage of transistor ('rFt3) (about O, a V), so the solar cell Unless the output voltage of (BTl) is approximately L6V or higher, power cannot be supplied to the scale basic circuit (MC).

However, if (TR4) is a FIT (NPll) transistor, add the voltage between the emitter and collector of each transistor (TR3) (TR4) and get the 9-value (0,6+0.8-
Power cannot be supplied unless the voltage is above L2V).

By the way, the scale itself is often used under fluorescent lights, such as in the kitchen, and the solar cell (B'rl) is not provided with sufficient illuminance, causing a problem with the above circuit.

Problems to be Solved by the Invention The problems to be solved by the present invention are to improve the power supply circuit so that sufficient power can be supplied to the basic circuit of the scale even when the output voltage of the solar cell is low. be.

2) Means for solving the problem A basic scale that detects the weight of the object to be weighed by a change in capacitance, converts the oscillation output of an oscillation circuit corresponding to the change in capacitance into weight, and displays it on the display. a solar cell and an auxiliary battery connected in parallel to each other to supply power current to the scale basic circuit, and a first battery connected to both batteries respectively;
A second switching means and a control switching element connected to both of the switching means and controlling the switching means on and off based on the output voltage of the solar cell are provided.

(e) Function If the voltage of the solar cell is sufficient to turn on and off the switching elements, sufficient power can be supplied to the basic circuit of the scale even at a low output voltage, and the scale can be used for lighting in kitchens, etc.

(F) Embodiment The power supply circuit of the present invention will be described below with reference to an embodiment of the power supply circuit of an electronic scale shown in the drawings.

(4) a static processor that detects a change in capacitance due to displacement of the capacitor as a change in the oscillation frequency of the oscillation circuit using an oscillation circuit configured with a time constant circuit including a sensor;
is the AND of the sampling output signal and the output signal of the capacitance-frequency converter 12) through nine circuits (5), and the output of this AND circuit (6) is connected to the input terminal (
a counter that counts the number of pulses input through the
(6) is connected to the display output terminal (0σT2) of the microprocessor (3).
) is a liquid crystal display unit that digitally displays the weight of the object to be weighed +11 based on the weight display output of the weighing object +11. The counter (4)
(2) is a heavy-capacitance conversion unit constituted by a parallel plate capacitor that is displaced against the microprocessor;
inputs the above-mentioned conde numerical value to the microprocessor (3) as a weight data signal. Each of the above parts is supplied with power by a power supply circuit (9).

Normal weighing operations are possible with the above circuit configuration.

That is, the weight of six objects to be weighed (1) placed on a total of one plate (11) is converted into the bond capacitance of a capacitor in the weight-capacitance converter (1), and the capacitance - Frequency conversion section (2)
It is output from On the other hand, the built-in clock circuit of the microprocessor (3) outputs a sampling pulse having a constant width to its output terminal (CK), and the output signal of the output terminal (CK) is transmitted to the frequency converter (2). Together with the output, it is input to the AND circuit (6), where both are subjected to a logical operation (AND operation), and the AtfI) circuit (
The output of step 5) is input to the counter (4). The counter (4) passes through the AND circuit (5) while the microprocessor (3) is outputting a sampling pulse.
1Pr+21 output pulses are counted and the counted value is output to the microprocessor (3).

The microprocessor (3) reads the above pulse count value and calculates the number of pulses at heavy tOg (only one plate in total) and Xg.
The number of pulses of the clock (total of one object to be weighed) is calculated, and the calculation result is converted into weight and output from the output terminal (Oστ2) to the liquid crystal display section (6). )
The weighed weight of the object to be weighed + 11m is displayed.

By the way, (7) is built in the microprocessor (3), and (8) is set by the key matrix circuit (7), and when nine hours have elapsed, the alarm output terminal (8) of the microprocessor (3) is set.
This is a buzzer circuit that includes a buzzer (not shown) that is driven by an alarm signal output from the 0σTl) and emits an alarm sound. The timer time setting keys of the key matrix circuit (7) include a key for setting the digit of 10 minutes and a key for setting the digit of 1 minute. To explain the operation method of the above-mentioned alarm means, first, the timer mode setting key is pressed to set the built-in circuit of the electronic scale to the timer mode, and the weighing operation of the scale is interrupted. Then, operate the timer time setting key to set the time from 0 to 99 minutes.6 Next, when the timer mode setting key is pressed again, the timer circuit in the microprocessor (3) starts operating. The reference time for this timer circuit is a day oscillation circuit comprised of a crystal oscillator in the clock circuit of the microprocessor (3).

The alarm output of the microprocessor (3) is output to the alarm output terminal (Olllrrl) twice by the arithmetic circuit in the microprocessor (3), once 10 seconds before the set time and again at the set time.
) is programmed to issue an alarm output. The alarm output 10 seconds before the set time is 2048Hz or iJ:
A single pulse of 4098 Hz is followed by a predetermined interval, and the second alarm output is 2048 Hz.
A pair of pulses with small intervals of 4098Hsi continue with a predetermined interval. Therefore, the buzzer circuit (8) emits an alarm sound of "beep...beep" when 10 seconds remain before the timer setting time, and "beep...beep" when 0 seconds remain.

On the other hand, the IJ Lux path (7) can also be used as follows. That is, the key matrix circuit (7) is provided with a preset mode key, a 100g digit key, and a 10g digit key for setting the required weight in advance. After doing this, first press the preset key to interrupt the operation of the electronic scale and put the built-in circuit into preset mode. At this time, the 1g digit of the set weight is always set to O. Therefore, the set weight can be set in increments of 10 g between 10 and 990 g. Then, press the preset mode key again to set the light value and store the light value in the memory of the microprocessor (3), causing the microprocessor (3) to calculate the standard value of the warning sound immediately before the set weight is reached.

The standard value of the warning sound is when the setting 1t is 50g or more, the setting type 11X90% setting heavy dragon is less than 50g, and the setting weight is 5g.

After calculating the standard value of the warning sound and storing it in the memory of the microprocessor (3), the normal electronic scale weighing mode is returned to.

When the set weight is 50g or more, it is okay if the refinement is a little rough, so set weight > measured weight ≧ set weight x 90 cm. Also, when the set weight is 50 g or less, it is necessary to set the refined nitrogen higher. The microprocessor (3) supplies an alarm output to the buzzer circuit (8) so as to generate the first alarm signal when weight>measured weight≧setting amount t-5g.

Note that the set weight data and the standard value of the warning sound will not disappear unless the microprocessor (3) is reset (for example, the power is turned off), so it is possible to repeatedly measure the same weight over and over again.

Next, details of the power supply circuit (9) will be explained based on the diagram @L. In the figure, the negative terminal of the solar cell (E'rt) and the negative terminal of the lithium battery (BT2) are connected to form a common ground (GND).
) is connected to the emitter terminal of the transistor C'rat of vJl via a backflow prevention diode (Dl), and the positive terminal of the lithium battery (BT2) is connected to the second
The collector terminals of both front transistors (TR1) (TR2) are connected to the voltage stabilizing circuit (SC) via a resistor (R4), and this voltage stabilizing circuit is connected to the emitter terminal of the transistor (TR2). (8C) Weigh basic circuit (M
C) and both the transistors (TRI)
Connect each base terminal of (TR2) to a pace resistor (R3) (
'R5) is connected to the collector terminal of @4 transistor (TR4), and the emitter terminal of this fourth transistor CTR4) is connected to the base terminal of the third transistor (TR3) through resistors (R6) (R7). ground (GND)
) is connected to the scale basic circuit (MC) via a resistor (R6), and the voltage dividing point (2) between the resistor c'Ft6) and the resistor (R7) is connected to the Connected to the positive terminal of a lithium battery (BTz). The fourth transistor (T'R4) connects its base terminal to the solar cell (BT1') via a resistor (Rt).
) and connected to the ground (GND) via a resistor (R2).

In this circuit, when light with sufficient illuminance is incident on the thick battery (BTI), when the switch (8W1) is instantaneously closed, the lithium battery CB2) is connected to the third transistor (TR3) through the resistor (R6). ), the transistor (TR3) becomes conductive.

The output voltage of the solar cell (BTx) is high, and current is supplied from the solar cell (BTt) to the base of the fourth transistor (TR4), so that this transistor (TR4) also becomes conductive. In this way, when the 3.4th transistor (TR3) (TRY) becomes conductive, the 4.2nd transistor (TRs 'J(TR2')
) flows through these transistors (TR1).
(TR2) becomes conductive. In this case, solar cell CBTx)
Even if there is a voltage difference between the voltage of the solar cell CB'1'1) and the lithium battery (BT2),
If the voltage is T2), the current supply capacity of the solar cell (BTI) is small, and when the scale basic circuit (MC) is connected, the solar cell (
The voltage across BTt) decreases, and this voltage difference apparently disappears. -Voltage of lithium battery (BT2)>Solar battery (B
'rl), charging of the solar cell (BTI) is suppressed by the diode (Dl), so the batteries CB'r1) (BT2) will not charge each other.

When the first and second transistors (TRIXTR2) conduct, power is supplied from the solar cell (BT2) and the lithium battery (BT2) to the voltage stabilization circuit (8C), and the stabilized voltage power is supplied to the scale basic circuit (8C). MC').

When power is supplied to the scale basic circuit (MC), the voltage at the voltage division point ■ becomes l”Hl ghJ level, and this voltage division point (1)
becomes the power supply for the microprocessor (3) of the balance basic circuit (MC), and the microprocessor (3) starts operating. However, if the liquid crystal display (6) displays the same value for 2 minutes, the microprocessor (3) The base current continues to be supplied to the third transistor (TR3) even if the switch (gwl) is opened.

In addition, the voltage of the lithium battery CBT2) is the voltage of the transistor (
The saturation voltage between the emitter and collector of TR2) drops, but the flowing current is several hundred μA - a normal basic circuit (MC
), this voltage drop is so small that it can be ignored. In this way, the voltage of the lithium battery (BTz) hardly drops and the basic circuit (
MC). The other operations of such a circuit are the same as those described with reference to FIG. 3, and will therefore be omitted here.

In the above embodiment, the power supply circuit (9) of the scale basic circuit (MC)
) is turned off in the following cases.

a. When the light to the solar cell (BTx) is blocked, the fourth transistor (TR4) is turned off, and both the first and second transistors (TRI) and (TR2) are turned off.

b, The same value is displayed on the liquid crystal display +81 for more than 2 minutes, the voltage level at the voltage dividing point (to) becomes rIJO-r-J, the third transistor (TR3) is turned off, and the "11.2) transistor (TRI) (TR2) are both turned off.

(G) Effects of the Invention As described above, the present invention detects the weight of an object to be weighed by a change in capacitance, and converts the oscillation output of an oscillation circuit corresponding to the change in capacitance into weight. It has a scale basic circuit that is displayed on the display, a solar cell and an auxiliary battery that are connected in parallel to each other in order to supply power current to the scale basic circuit, and a first and second battery that are connected to both batteries, respectively. switching means;
By providing a control switching means that is connected to both of these switching means and controls the switching means on and off based on the output voltage of the solar cell, it can be used even in a dark place (50 to 100 LuX) compared to a conventional power supply circuit. Moreover, by using the solar cell and the auxiliary battery in combination, it is possible to suppress the consumption of the auxiliary battery to a small level.

[Brief explanation of the drawing]

FIG. 1 is an implementation circuit diagram showing the power supply circuit of the electronic scale of the present invention,
FIG. 2 is a block diagram showing an implementation circuit diagram of an electronic scale employing the power supply circuit of FIG. 1, and FIG. 3 is a conventional circuit diagram corresponding to FIG. 1. (10...Object to be measured, (G)...Display section, (MC)
...Basic scale circuit, (BTI) ...Solar cell, (BT
2)...Lithium battery (auxiliary battery), (TRx)...
- First switching means, ('TR2)...Second switching hand Q, (''4)...Control switching means.

Claims (1)

[Claims] (1) The scale has a basic circuit that detects the weight of the object to be weighed by a change in capacitance, converts the oscillation output of an oscillation circuit corresponding to the change in capacitance into weight, and displays the weight on the display. , a solar cell and an auxiliary battery connected in parallel to each other for supplying power supply current to the scale basic circuit, first and second switching means connected to both the cells, respectively, and a solar cell connected to both of the switching means. A power supply circuit for an electronic scale, comprising a control switching means for controlling on/off of the switching means based on the output voltage of a battery.