JPH03564B2 - - Google Patents

Description

[Detailed description of the invention]

This invention relates to postage scales. In recent years, electronic scales that process data digitally have been developed as postage scales.
It is desirable that a device that performs metering processing electrically be as power-efficient as possible. Especially when considering simple devices that use batteries as a power source, power saving becomes an extremely important issue as it can extend the battery life. By the way, when weighing a postage using a postage scale, the postage is determined according to the weight of each postal item. Considering this, once the postage has been weighed and the postage is known, the postage can be weighed. After unloading the mail, the next mail item is placed on the scale and weighed, and even though the previous mail item is on the scale, the next mail item is not placed on the scale. If it is, it will be an incorrect measurement. The present invention has been made in view of these points, and it is an object of the present invention to provide a postage scale that can save power and prevent charge specification due to incorrect weighing. Embodiments of the present invention will be described below with reference to the drawings. FIG. 1 is a perspective view showing the external appearance, and numeral 1 indicates a housing in which circuit components such as a load cell and a microprocessor, which will be described later, are housed. A pedestal 2 connected to a load cell is placed on the top of the casing 1. The front part of the casing 1 is sloped low toward the front, and a postage insertion part 4 is formed on the slope, and a postage insertion part 4 into which a postage table 3 can be inserted and removed in the direction indicated by the arrow in the figure is formed. Sixteen weight indicator lamps 5a, 5b, 5c, . . . 5p are provided below as display elements corresponding to the weight ranges of the postage table. Further, below the postage table insertion section 4, a zero weight indicator lamp 6 is provided which is located to the left of the weight indicator lamp 5a that indicates the minimum weight range, and a zero weight indicator lamp 6 is provided which is located below the lamp 6 to indicate when it is time to replace the battery. A warning lamp 7 for display is provided, and a start switch 8 is provided below the weight indicator lamp 5p on the right side. Figure 2 shows the state when the postage table 3 in pound weight unit system is inserted into the postage table insertion section 4.
The weight values are printed in 1-ounce increments from 1 to 16 ounces (OZ), and the charges for first class, air mail, and third class are printed for each weight value. The weight value of 1 to 16 ounces in price list 3 is displayed on each of the weight indicator lamps 5a, 5b, 5.
It corresponds to c,...5p. FIG. 3 shows a control circuit housed in the casing 1, and 11 is a battery as a power source. A constant voltage circuit 12 is connected to the battery 11 via the start switch 8 which is closed only during extrusion, and a series voltage dividing circuit 15 formed by connecting a resistor 13 and a resistor 14 in series is connected. Further, a switch circuit 16 is connected to the battery 11, which together with a microprocessor to be described later forms a power cutoff control means. The constant voltage circuit 12 includes an NPN type first transistor 17 and a constant voltage diode 18, and connects the collector of the first transistor 17 to the battery 1 via the start switch 8.
1, and connect it to the positive terminal of the voltage regulator diode 1.
8 is connected to the base of the first transistor 17, and its anode is connected to the negative terminal of the battery 11. And the first above
A resistor 19 is connected between the collector and base of the transistor 17. The switch circuit 16 is
The emitter of the second transistor 20 is connected to the positive terminal of the battery 11, and the base of the second transistor 20 is connected to a resistor. 22 and the third transistor 21 are connected in series to the negative terminal of the battery 11. The collector and emitter of the second transistor 20 are connected in parallel to the start switch 8. Resistors 23 and 24 are connected between the base and emitter of the second and third transistors 20 and 21, respectively. The base of the third transistor 21 is connected via a resistor 26 to a signal output terminal of a microprocessor to be described later. an output end of the constant voltage circuit 12;
That is, a load cell 26, a signal amplifier 27, a zero point setting circuit 28,
Integral type A/D converters 29 are connected to each. Further, a reset signal generator 30 is connected to the output terminal of the constant voltage circuit 12. Furthermore, a microprocessor 32 is connected to the output end of the constant voltage circuit 12 via a diode 31. The load cell 26 has four resistors 33, 34, 3
5 and 36 are connected in a bridge shape, the connection point a of the resistors 33 and 36 and the connection point b of the resistors 34 and 35 are connected to the output end of the constant voltage circuit 12, and A voltage signal corresponding to the load is output between the connection point c and the connection point d between the resistors 35 and 36. That is, the output V _L generated between the connection points c and d of the load cell 26 is given by the following relational expression: V _L =F _X /F _o ·K · V _E . However, F _X is the load (Kg) applied to load cell 17, F _o is load cell 1
7, the rated load (Kg), K is the output voltage (mV/V) per 1 (V) of applied voltage when the rated load is applied to the load cell 26, and V _E is the output voltage of the constant voltage circuit 12 applied to the load cell 26. It is the output voltage (V). The signal amplifier 27 includes operational amplifiers 37 and 38, and the connection point d of the load cell 26 is connected to the amplifier 37.
The connection point c of the load cell 26 is connected to the non-inverting input terminal (+) of the amplifier 38. and the amplifier 3
The output terminal of the amplifier 7 is connected to its own inverting input terminal (+) via a resistor 39, and is also connected to the inverting input terminal (-) of the amplifier 38 via a resistor 40. In addition, the output terminal of the amplifier 38 is connected to a resistor 41.
It is connected to its own inverting input terminal (-) via. The amplification factor G of this signal amplifier 27 is given by the relational expression G=R ₄₁ /R ₄₀ . However, R ₄₁ is the resistance value of the resistor 41, R ₄₀ is the resistance value of the resistor 40, R ₄₀ is equal to the resistance value of the resistor 46, and R ₄₀ is equal to the resistance value of the resistor 39. The zero point setting circuit 28 includes a resistor 4
2. Consisting of a series circuit of a potentiometer 43 and a resistor 44 and an operational amplifier 45, the series circuit is connected to the output terminal of the constant voltage circuit 12, and the movable terminal of the potentiometer 43 is connected to the non-inverting input of the amplifier 45. terminal (+), the output terminal of the amplifier 45 is connected to its own inverting input terminal (-), and the signal amplifier 27 is connected to the inverting input terminal (-) of the amplifier 37 via the resistor 46. There is. The output voltage V _Z of this zero point setting circuit 28
is given by the relational expression V _Z = R ₄₄ + R' ₄₃ / R ₄₂ + R ₄₃ + R ₄₄・V _E ...... However, R ₄₂ is the resistance value of resistor R ₄₂ , R ₄₃ is the total resistance value of potentiometer 43, R' ₄₃ is the resistance value set by the movable terminal of potentiometer 43, and R ₄₄ is the resistance value of resistor 44. It is. Then, the output of the signal amplifier 27, that is, the output of the operational amplifier 38, is transferred to the analog 1 switch 4.
7 to the A/D converter 29. Also, the resistors 13 and 1 of the series voltage dividing circuit 15
4 connection point outputs are supplied to the A/D converter 29 via an analog 2 switch 48. Both switches 47 and 48 are connected to a switch drive circuit 4 controlled by a microprocessor 38.
It is designed to be ON/OFF controlled by 9. The A/D converter 29 is an operational amplifier 50
an integrator consisting of a plurality of analog switches 51,
51, . . . and a control circuit 52 that controls each of the analog switches, inputs the integrator output at a predetermined timing, and generates count data corresponding to the voltage level. The input voltage Vin from the signal amplifier 27 to the A/D converter 29 is given by the relational expression Vin=G・V _L +V _Z .
The count data output N _R from is given by the relational expression N _R Vin/V _E・N _S ……. From the above formula, this relational expression becomes: N _R = N _S /V _E・(G・V _L +V _Z )……. Furthermore, from the above formula, N _R = N _S・(R ₄₁ /R ₄₀・F _X /F _o・K+R ₄₄ +R′ ₄₃ /R ₄₂
+R ₄₃ +R ₄₄ ) ...... The sensitivity of the A/D converter 29 (the relationship between the number of counts and the input voltage) is determined by the movement of the potentiometer 54 in a series circuit of a resistor 53, a potentiometer 54, and a resistor 55 connected to the output terminal of the constant voltage circuit 12. The terminals can also be changed by adjusting them. The microprocessor 32 has a built-in CPU (Central Processing Unit), ROM (Read Only Memory), RAM (Random Access Memory), etc., and operates an A/D converter based on program data set in the ROM. Count data is read from 29 and calculated using a calculation register formed in RAM to obtain a weight value. Then, a weight indicating lamp to be lit is determined based on the calculated weight value, and a lamp specifying signal is supplied to the display 56. The display 56 receives a lamp designation signal from the microprocessor 32 and selectively controls the lighting of each of the weight indicator lamps 5a to 5p. Further, the microprocessor 32 reads the count data from the A/D converter 29 at the timing when the analog 2 switch 48 is turned on by the switch drive circuit 49, checks the battery voltage _VB , and checks the battery voltage _VB. However, when the output of the constant voltage circuit 12 falls below the voltage level α which is set slightly higher than the voltage level β at which the constant voltage output state cannot be maintained, that is, when it is determined that α>V _B ≧β, the warning lamp 7 is turned on. I am trying to control the lighting. The reset signal generator 30 supplies a reset signal to the microprocessor 32 when power supply is started. The RAM in the microprocessor 32 has a memory as shown in FIG.
6 count data registers _M01 to _M06 ,
MAVE average count data register,
The MZER zero point register, the MTRU true value weight register, the MT timer, the Init/F initial flag memory, the Bef/F before-lag memory, etc. are formed. FIG. 5 is a flowchart showing the main processing performed by the microprocessor 32. Based on this, the control of the microprocessor 32 will be described. When the power is turned on, a reset signal is input from the reset signal generator 30. First, the initial settings will start. This initial setting involves clearing the RAM and then setting various flags for initial processing. Then, the switch drive circuit 49 is controlled to turn on the analog 1 switch 47 and turn on the analog 2 switch 48.
is turned off, and a high level signal is supplied to the base of the third transistor 21 of the switch circuit 16. Further, the timer MT is set to start a counting operation, and the weight indicating lamps 5a to 5p, 6 of the display 56 and the warning lamp 7 are turned off. Furthermore, the initial flag memory Init.F is set to zero. Next, count data is read from the A/D converter 29 into the count data register _M01 . At this time, the count data stored in M ₀₁ to _{M 05} are shifted to M ₀₂ to M ₀₆ , respectively. Next, "1" is added to Init.F. Next, flicker prevention processing is performed. This is done by calculating the average value of the count data contained in M ₀₁ to _{M 06} and storing the average value count data in MAVE. Next, check whether Init・F has become "8". If it is "8", the contents of MAVE are stored in the zero point register MZER as zero point data. This is “1” in Init・F after the power is turned on.
The zero point setting is prohibited until the addition routine has been repeated eight times, and the zero point setting is made after the circuit operation has stabilized to ensure reliability. Further, Init.F is counted up sequentially and when it reaches "A", it is reset to "9" so that it does not exceed "A". This is inconvenient because if you do not return it to "9", Init・F will count sequentially and eventually reach "F", then return to "0", and then become "8" again, so you will have to set the zero point many times. This is because Next, calculate the weight. This is done by subtracting the contents of the zero point register MZER from the contents of the average value count data register MAVE and storing the result in the true value weight register MTRU. Next, it is checked whether the content of MTRU is larger than zero, and if it is not larger, "1" is set in the before flag memory Bef.F. If it is larger than zero, then
Check if "1" stands in Bef・F,
If "1" is set, the timer MT is reset and restarted. And clear Bef・F to zero. This indicates that when the zero point is set after the power is turned on, MTRU = 0, then Bef・F = 1, and then when weighing starts and the content of MTRU becomes greater than zero, the timer is restarted. There is. Next, check whether the weight unit is set to the pound system or the gram system. This can be done, for example, by setting the weight unit system using the jumper wire built into the housing 1, reading the setting state of the jumper image at the time of initial setup, and setting a flag. You can do it by holding it. If the pound system is set, the lamp to be lit is determined based on the preset relationships in Table 1, and if the gram system is set, the lamps to be lit are determined based on the preset relationships in Table 2. The lamp to be lit is then determined. Also, when this check process is performed immediately after zero point setting, it is checked whether the set zero point is within the preset allowable zero point range, and if it is within that range, zero weight is indicated. It is determined to turn on the lamp 6 to control the display 56, and if the weight is not within the range, it is determined to blink the zero weight indicating lamp 6 and the display 56 is controlled. Next, check if the weight value of MTRU is less than zero. This occurs, for example, when the base plate 2 is lifted, and if the weight value is smaller than zero, the display 56 is controlled and the weight indicator lamps 5a to 5p are cycled from right to left, that is, from lamp 5p to lamp 5a. to flash. weight

【table】

【table】

[Table] If the value is zero or more, then check whether the weighing is over. This is done by checking whether the weight unit is over 16 ounces if the unit is in pounds, or over 500 grams if the unit is in grams. If the weight value is over weighed, the display 56 is controlled to cause the weight indicator lamps 5a to 5p to flash cyclically from left to right, that is, from lamp 5a to lamp 5p. Further, if the weight value does not exceed the weighing amount, the display 56 is controlled to light up the weight indicator lamp corresponding to the weight value in accordance with the lamp determination. When this process is completed, switch drive circuit 4
9 to turn off the analog 1 switch 47 and turn on the analog 2 switch 48. Then, the output of the A/D converter 29 based on the voltage signal at the voltage dividing point of the resistors 13 and 14 is checked, and it is checked whether the voltage V _B of the battery 11 is equal to or higher than the level α. This is done by detecting how much count data the A/D converter 29 outputs based on the voltage signal from the voltage dividing point of the resistors 13 and 14, which is correlated with the battery voltage. When it is determined that the battery voltage V _B is higher than α, the switch drive circuit 49 is controlled and the analog 1 switch 4 is activated.
7 is turned ON, analog 2 switch 48 is turned OFF, and the routine returns to inputting count data. If the battery voltage V _B is not higher than α, then it is checked whether it is higher than level β. And α＞
If V _B ≧β, turn on the warning lamp 7, and then check whether the timer MT has reached the time end. This is done by checking whether the count value of the timer MT is a preset value, for example, assuming that it counts "1" every 0.5 seconds, it is "40", that is, 20 seconds have elapsed. and
If 20 seconds have not passed, switch drive circuit 4
9, the analog 1 switch 47 is turned on, the analog 2 switch 48 is turned off, and the routine returns to inputting count data. If 20 seconds have elapsed, it is determined that the time has come to an end, and the input voltage to the base of the third transistor 21 of the switch circuit 16 is switched from high level to low level. Also, in the above battery voltage check, the battery voltage
When it is determined that V _B is smaller than β, the base voltage of the third transistor 21 of the switch circuit 16 is immediately switched from high level to low level. With this configuration, when the start switch 8 is turned on, the constant voltage circuit 12 is connected to the battery 11, and the output of the constant voltage circuit 12 is connected to the load cell 26, signal amplifier 27, zero point setting circuit 28, A/D converter 29, and reset. The signal generator 30, microprocessor 32, etc. are supplied with power. The microprocessor 32 has a reset signal generator 30.
A reset signal is input from , and initial processing is performed. As a result, a high level signal is supplied from the microprocessor 32 to the base of the third transistor 21 of the switching circuit 16, and the switching circuit 16 turns on the third transistor 21 and turns on the second transistor 21.
The transistor 20 of is turned on. Thereby, even if the start switch 8 returns to its original open state, the constant voltage circuit 12 will remain connected to the battery 11. Count data is then read from the A/D converter 29 into the microprocessor 32, and the zero point is set after a certain period of time. If the zero point setting data falls within a preset allowable zero point range, the zero weight indicator lamp 6 lights up to notify the user of this fact. Further, if the zero point setting data is not within a preset allowable zero point range, it is determined that something is placed on the base plate 2, and the zero weight indicator lamp 6 flashes to notify the user.
In this case, if the object is removed from the base plate 2 and the start switch 8 is turned on again, the correct zero point setting will be performed. Even if the zero point is set correctly, if the metering is not performed for 20 seconds after the start switch 8 is turned on, the timer
When MT reaches the time end, the microprocessor 32 switches the high level signal to the base of the third transistor 21 to a low level signal, turns off the second transistor 20, and disconnects the battery 11.
Also, if there is a weighing operation during these 20 seconds, MTRU>0
The timer MT is then reset and restarted. And after the timer MT restarts
If the weighing state is left undisturbed for 20 seconds, the microprocessor 32 switches the high level signal to the base of the third transistor 21 to a low level signal and also disconnects the battery 11. Also, if you finish weighing within 20 seconds after the start of weighing, set the load to zero, that is, MTRU = 0, and then re-weigh, Bef・F, which was once cleared to zero, will be set to "1" again, so the timer MT stands for MTRU
>0, it will always be reset and restarted. Therefore, as long as the next weighing is carried out within 20 seconds after the last weighing and the scale is returned to zero, the timer will not restart repeatedly and the battery 11 will not be disconnected. Also, if you forget to remove the mail from tray 2 even after the previous weighing is complete, and weigh the next mail, the weight of the previous mail will be added to the weight. This will result in incorrect measurement. However, at this time, BBef and F are still cleared to zero at the start of the previous measurement, and even when the next measurement starts, the timer
Since the MT is not restarted, the timer MT immediately reaches its time end, and the switch circuit 7 is controlled by the microprocessor 32 to restart the battery 1.
1 is disconnected and the scale cannot operate. Therefore, the user will not be able to read the charge and will be aware of the incorrect metering. In this way, it is possible to prevent incorrect charge specification due to incorrect metering. The microprocessor 32 also performs routine 1
The switch drive circuit 49 is controlled to switch the analog switches 47 and 48 every cycle, and the resistor 1
3 and 14 to the A/D converter 29
The voltage _VB of the battery 11 is directly checked by checking the count data from the . When it is detected that the voltage V _B has fallen below the level α, which is set slightly higher than the level β at which the output of the constant voltage circuit 12 cannot maintain a constant voltage, the microprocessor 32 turns on the warning lamp 7. Notifies you when to replace the battery. Further, as soon as a situation occurs in which the voltage V _B falls below the level β, the high level signal to the base of the third transistor 21 is switched to a low level signal, the battery 11 is disconnected, and the function as a scale is stopped. Further, when mail is placed on the tray 2 and the weighing operation is started, a voltage signal corresponding to the load is output from the load cell 26, and the voltage signal is amplified by the signal amplifier 27 and input to the A/D converter 29. .
Then, the A/D converter 29 outputs count data corresponding to the input voltage. The microprocessor 32 takes this count data into the RAM count register _M01 . And M ₀₁ ~
Calculate the average value of the six count data of M ₀₆ and store it in the average value count data register MAVE,
Furthermore, MAVE-MZER is calculated and stored in the true value weight count data register MTRU.
Then, if the weight unit is set to the pound system, the contents of the MTRU are converted to a weight value in ounces, and the weight indicator lamp that should be lit is determined based on the relationship in Table 1. Determine. For example, if the weight value is 12.5 ounces, it is decided to turn on the weight indicator lamp 5m. In this case, since the weight is within the weighing range, the microprocessor 32 displays the display 56 and lights up the weight indicator lamp 5m. Therefore, if a postage table 3 as shown in FIG. 2 is inserted into the postage table insertion section 4, the fees for "first class,""airmail," and "third class" can be seen at a glance. For example, if the weight unit is set to the gram system, it is converted to a weight value in grams, and it is determined to which weight value the weight value corresponds based on the relationship shown in Table 2, and the weight indicator lamp to be lit is determined. If the weight value is, for example, 85 grams, it is decided to turn on the weight indicator lamp 5d. Therefore, in this case, a price list with prices set in units of grams may be inserted into the insertion section 4. Furthermore, when the microprocessor 32 determines that the weight value read by the weighing operation exceeds the weighing value, the microprocessor 32 notifies the user by blinking each of the weight indicator lamps 5a to 5p sequentially from left to right (from 5a to 5p). Therefore, the user can immediately know that the weighing amount has exceeded. Also, when the weight value is smaller than zero, this occurs when mail is unloaded from the tray 2 and the tray 2 is lifted by something, but in this case each weight indicator lamp 5
A to 5p can be notified by blinking sequentially to the right or left (5p to 5a). As described above, in the device of this embodiment, if the start switch 8 is turned on and the metering is not performed for 20 seconds, the battery 11 is immediately disconnected to prevent the battery 11 from being exhausted. Further, when the first measurement is started within 20 seconds after the start switch 8 is turned on, the battery 11 is kept connected and the measurement process is performed. Then, within 20 seconds from the start of weighing, the mail is unloaded from tray 2, and the next mail is placed on tray 2.
If the weight is placed on the screen, the next weighing process will continue. Therefore, the power supply can be maintained by simply exchanging mail, and responsiveness to continuous weighing operations is excellent. However, if a mistake is made such as placing the next mail item on tray 2 without unloading the mail item, the timer MT will continue counting without being reset. Since the battery 11 is disconnected and cannot function as a scale, it is possible to prevent incorrect charge specification due to incorrect weighing. In the above embodiment, the time end time of the timer was set to 20 seconds, but the time end time is not limited to this and may be set arbitrarily. As detailed above, according to the present invention, weighing operation is possible by turning on the power, and in a postage scale that specifies postage by weighing, a timer is started in response to turning on the power. At the same time, the timer is restarted in response to the start of weighing, and after the weight value returns to zero after weighing, the timer is restarted when the next weighing is started, and when the timer counts a predetermined time, the timer is restarted. Since the power supply is cut off, power consumption is prevented even if the product is left unattended after the power is turned on or after weighing, resulting in power savings.
It is particularly useful when batteries are used as a power source, and it has excellent operability and responsiveness for continuous weighing of mail items. To provide a postage scale capable of preventing erroneous charge specification by immediately disconnecting the power supply at the time end of a timer even if there is an erroneous measurement.

[Brief explanation of the drawing]

The figures show an embodiment of the present invention, in which Fig. 1 is a perspective view showing the external appearance, Fig. 2 is a plan view showing the structure of the display section, Fig. 3 is a circuit configuration diagram, and Fig. 4 shows the main components of the RAM. FIG. 5, which shows the memory configuration, is a flowchart showing the main processing performed by the microprocessor. 11...Battery, 16...Switch circuit, 26...
...Load cell, 29...A/D converter, 32
...Microprocessor, Bef/F...Before/Flag, MT...Timer.

Claims (1)

[Claims] 1. In a postage scale that enables weighing operation by turning on the power and specifies postage by weighing, it starts in response to turning on the power, and resets and restarts in response to the start of weighing. and a timer that is reset and restarted when the weight value returns to zero after weighing, and a power cutoff control means that controls to cut off the power supply when a predetermined time has elapsed since the timer started. and postage scales.