JPH0354820B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION (Field of Application) The present invention relates to a switch-on detection device for an operating section having a plurality of operating switches.

(Prior Art) A conventional device of this type will be explained with reference to FIGS. 1 and 2. FIG. FIG. 1 shows an operation panel 101 of an electronic copying machine. For example, an operator who wishes to make copies presses the number setting key 103 to set the number of copies, and then presses the copy start key 102. A control section (not shown) constantly monitors which key switch is pressed by the operator, detects the pressed key switch, and performs predetermined control.

FIG. 2 shows an example of a conventional switch-on detection device for an operating section. In the figure, reference numeral 201 is an operation panel, in which a plurality of key switches S ₁ to G ₁₆ are connected in series with backflow prevention diodes D ₁ to _{D 16} , respectively.

202 is a control unit, and the microprocessor 2
11, currents IS1 to IS4 are sequentially supplied from the current supply type driver 208 to the operating unit 201 through the current supply line 206 with temporally shifted phases. If any of the key switches S ₁ , S ₅ , S ₉ , and S ₁₃ is pressed during the time when the current IS1 is supplied, the signal is detected via the signal detection line 207 corresponding to the pressed key switch. Current flows through a load resistor 210 connected to the line. Therefore, a high level signal is input to the buffer 209 connected to the signal detection line, and the microprocessor 211
A signal is transmitted to

Similarly, during the times when currents IS2 to IS4 are supplied to the operation unit 201, (S ₂ , S ₆ , S ₁₀ , S ₁₄ ),
The key switches (S ₃ , S ₇ , S ₁₁ , S ₁₅ ) (S ₄ , S ₈ , S ₁₂ , S ₁₆ ,) will be detected.

As described above, conventional devices generally include m current supply lines, n signal detection lines, and switches and switches that connect these current supply lines and signal detection lines arranged in a matrix to each other. It is formed by a circuit consisting of a series circuit of backflow prevention diodes. This device time-divides the m current supply timings so that they do not overlap with each other,
By detecting the voltage of n signal detection lines,
It is designed to be able to detect m×n key switches.

However, according to the conventional device having such a configuration, at least (m+n) wire connecting members are required to connect the control section and the operation section. Therefore,
When the number of key switches increases, there are disadvantages in that the number of wiring materials increases and the device becomes complicated, and the volume occupied by the wiring materials cannot be ignored, resulting in an increase in the size of the device. Furthermore, the number of current drivers for supplying current to m current supply lines, the number of input buffers for detecting n signals, and n load resistors are required, which increases the number of components. , which has the disadvantage of reduced reliability. Furthermore, in the operating section, it is natural that m×n single-pole single-throw switches are required, but m×n backflow prevention diodes are also required, which has the drawback of low reliability and increased assembly man-hours.

(Objective) The present invention has been made to eliminate the above-mentioned drawbacks, and its purpose is to reduce the number of wiring materials connecting the control unit and the operation panel, reduce the number of component parts of the control unit and the operation unit, Another object of the present invention is to provide a highly reliable switch-on detection device for an operating section.

(Summary) In order to achieve the above object, the present invention comprises a plurality of operating switches each having one pole connected to a common line, a plurality of fixed resistors connected in series, and a plurality of fixed resistors connected in series. A predetermined voltage is applied to the fixed resistors connected between each of the connection points of the plurality of fixed resistors and their end points and the plurality of operation switches, and the plurality of fixed resistors connected in series. The present invention is characterized in that it includes means for applying voltage and means for detecting the output level of the common line, and that the control section and the operating section are connected by, for example, two wiring members.

(Example) The present invention will be described in detail below with reference to the drawings.

FIG. 3 is a circuit diagram of an embodiment of the present invention.

In the figure, 301 is an operation panel. This operation panel 301 is composed of n key switches S ₁ to Sn and 2n fixed resistors having a resistance value r for operating the main body of the copying machine (not shown). On the other hand, 30
2 is a control section (not shown) for controlling the main body of the copying machine. This control section 302 is composed of a microprocessor 303, an A/D converter (analog-to-digital converter) 304, a fixed resistor 305, and other control circuits (not shown).

The n key switches S ₁ to Sn on the operation panel 301 are single-pole, single-throw push switches. One pole of each key switch is connected to the common line 307, and the other pole is connected to each of the resistor strings in which n fixed resistors are connected in series through the fixed resistor having the resistance value r. Resistor connection points P ₁ , P ₂ , P ₃ ,
..., connected to Pn. One end P ₀ of the resistor array is connected to the control unit 3 via a first common line 306.
A constant voltage source Vr is supplied from 02. On the other hand, the second
The common line 307 is connected to the fixed resistor 3 of the control unit 302.
It is grounded via 05. The second common line 3
The potential Vi of 07 is input to the A/D converter 304, converted into a digital value, and then transmitted to the microprocessor 303.

The potential Vi of the second common line 307 takes on different values depending on which one of the key switches S ₁ to Sn on the operation panel 301 is pressed. For example, when any one of the key switches S ₁ to Sn (x is an integer from 1 to n) is pressed, the potential Vi of the second common line 307 is determined by the following equation.

Vi= _R0 /(x+1)r+ _R0・Vr= _R0 /m・r+ _R0・Vr...(1) (However, m=2, 3, 4...n) Therefore, the microprocessor 303 is
By knowing the digital conversion value of Vi and comparing this value with the data corresponding to the key switches S ₁ to Sn stored in the memory of the microprocessor 303, it is possible to determine which of the n key switches of the operation unit 301. You can tell if the key switch has been pressed.

Next, when two different key switches, for example, Sx ₀ and Sx ₁ (x ₀ and x ₁ are integers from 1 to n, x ₀ < x ₁ ) are pressed at the same time, the equivalent of the operating section 301 in FIG. The circuit becomes as shown in FIGS. 4a and 4b. Therefore, the potential Vi' of the common line 306 is given by the following equation.

Vi′=R ₀ /2(x ₁ −x ₀ )+3/(x ₁ −x ₀ )+2・r
+R ₀・Vr=R ₀ /21+3/1+2・r+R ₀・Vr=R ₀ /Q・
r+R ₀・Vr...(2) However, Q=21+3/1+2 (1=1, 2, 3,..., n-1) By the way, the potential Vi of the common line 306 when only one key switch is pressed is (1)) and at the same time 2
Common line potential when two key switches are pressed
If we compare Vi′ (formula (2)), we always find that Vi≠Vi′.
The reason for this is that m in equation (1) is an integer, whereas Q in equation (2) cannot be an integer.

Therefore, the voltage value determined by equation (1) is stored in advance in the memory of the microprocessor 303, and when any other voltage is detected,
By discarding this detection data assuming that two key switches have been pressed, it is possible to detect erroneous operations such as pressing two key switches at the same time.

Note that the resistance r between points P0 and P1 in FIG. 3 is not necessarily necessary and may be deleted.

The present invention is not limited to electronic copying machines, but can be used in other electronic devices.

(Effects) As described above, according to the present invention, it is possible to detect which switch among n key switches has been operated by simply providing two signal lines between the operating section and the control section. I can do it. Therefore, the number of wiring members is significantly smaller than that of conventional devices, and therefore the structure is simple and highly reliable.

Further, according to the present invention, since the operating section can be constructed of only a fixed resistor and a single-pole switching switch, an inexpensive operating section can be realized with a small number of parts.

Further, according to the present invention, even if an operator accidentally operates two key switches at the same time, it is possible to detect that the operation is erroneous, so that a safe and highly reliable operation unit can be constructed.

[Brief explanation of drawings]

Figure 1 is a plan view of the operation panel of a conventional electronic copying machine.
Figure 2 is a circuit diagram of a conventional switch-on detection device.
Fig. 3 is a circuit diagram of an embodiment of the present invention, Fig. 4a,
b shows a circuit diagram when two key switches are pressed at the same time. 301...Operation panel, 302...Control unit, 303...Microprocessor, 304...A/D converter,
305... Fixed resistor, 306... First common line, 3
07...Second common line.

Claims (1)

[Claims] 1. A plurality of scanning switches having one pole connected to a common line, a plurality of fixed resistors connected in series, and a connection point of the plurality of fixed resistors connected in series. a fixed resistor connected between each of the plurality of fixed resistors and the plurality of operation switches, a means for applying a predetermined voltage to the plurality of fixed resistors connected in series, and an output of the common line. A switch-on detection device for an operating section, comprising: means for detecting a level, and detecting which operating switch is turned on by detecting the potential of the common line. . 2. A switch-on detection device for an operating section according to claim 1, wherein the potential of the common line is detected by A/D conversion.