JPH0453063Y2 - - Google Patents

Description

[Detailed description of the invention] [Purpose of the invention] (Field of industrial application) This invention connects a switch to a transistor in which multiple indicators are connected in parallel, and dynamically scans the switch with a microcomputer to determine whether the switch is open or closed. The present invention relates to an open/close determination device for a switch.

(Prior Art) FIG. 2 shows a general switch open/close determination device, in which 1 is a microcomputer. _X1
-X ₄ is a row line, Y ₁ and Y ₂ are column lines, and switches SW are arranged in a matrix at the intersections of these lines to form a switch matrix. One side of these row lines X ₁ to _{X 4} is connected to the input ports K ₀ to _{K 3} of the microcomputer 1, and the other side is connected to the power supply E through each pull-up resistor R, and the column lines
Y ₁ and Y ₂ are connected to the collectors of transistors Tr ₁ and Tr ₂ , respectively, and the bases of these transistors Tr ₁ and Tr ₂ are connected to output ports F ₀ and F ₁ of the microcomputer 1 via a resistor R. . Further, a plurality of light emitting diodes L are connected in parallel to the collectors of the transistors Tr ₁ and Tr ₂ , and the light emitting diodes L are each connected to output ports S ₀ to S ₄ of the microcomputer 1 via a resistor R. The microcomputer 1 updates the display data as needed, dynamically drives the output ports _S0 to _S4 and _F0 , _F1 , turns on the necessary light emitting diodes L, and performs dynamic scanning to determine whether the switch SW is open or closed. The input voltages of input ports _K0 to _K3 are read. For example, to determine whether the switch SW at the intersection of column line Y ₁ and row line X ₁ is open or closed, when transistor Tr ₁ connected to column line Y ₁ is on, input port _K Read the input voltage, and if this input voltage is “H”, the switch SW opens.
If it is "L", it is determined that the switch SW is closed. Here, the distinction between "H" and "L" is that when the microcomputer 1 is composed of C-MOS, when the input voltage is 4 to 5 V, it is "H", and when the input voltage is 4 to 5 V, it is "H" and 0 to 5 V.
When the voltage is 1V, it is "L", and between 1V and 4V, "H" and "L" are undefined. The conventional microcomputer 1 synchronizes the timing of the dynamic scanning of the switch SW and the dynamic driving of the light emitting diode L.

(Problem to be solved by the invention) In the above-mentioned conventional technology, dynamic scanning and dynamic driving are performed at the same timing,
Since the switch SW and the light emitting diode L are connected to the same transistor, for example, when one transistor Tr ₁ is on, this transistor
As the number of light emitting diodes L connected to Tr ₁ and turned on increases, the collector current of the transistor Tr ₁ increases, and the saturation voltage V _{CE (SAT)} between the collector and emitter increases. Therefore, when the number of light emitting diodes L that are turned on increases and the saturation voltage exceeds 1V, the input voltage at the input port will not change even if the switch SW connected to that transistor Tr ₁ is closed.
Since it was 1V or more, there was a possibility that it would not be determined as "L", and there was a problem that it would not be possible to accurately determine whether the switch SW was open or closed.

Therefore, the present invention has been made based on the above-mentioned problem, and an object of the present invention is to provide a switch open/close determination device that can accurately determine whether a switch is open or closed without being influenced by the display that is on. The purpose is to

[Structure of the invention] (Means for solving the problem) In the present invention, the microcomputer 1 is provided with means for turning off the display L when the switch SW is dynamically scanned.

(Function) Since only the current caused by the closed switch SW flows through the collector of the transistor Tr connected to the switch SW, accurate open/close determination of the switch SW is performed.

(Example) Hereinafter, an example of the present invention will be described in detail based on the drawings. The block diagram of the present invention is the same as the general block diagram shown in Figure 2, and the difference is that when the microcomputer 1 determines whether the switch SW is open or closed, the output ports _S0 to _S4 are set to "L". switch SW.
This is because the timing of the dynamic scanning of the light emitting diode L and the dynamic driving of the light emitting diode L are shifted.

In such a configuration, as shown in the flowchart of FIG. 1, the microcomputer 1 first turns the output ports _S0 to _S4 to "L" in step 1 to turn off all the light emitting diodes L. Then, in step 2, in order to determine whether the switch SW is open or closed, "H" is first output to the output port _F0 to turn on the transistor _Tr1 , and the input ports _K0 to _{K3 are} turned on.
Detects the input voltage of In this case, the transistor
Since the light emitting diode L is off, the collector current flowing through Tr ₁ is only the sum of the currents flowing through the closed switch SW. The current flowing through the switch SW is generally about 1/10 to 1/100 of the current flowing through the light emitting diode L, so many switches
Even when SW is closed, the saturation voltage between the collector and emitter of transistor Tr ₁ remains sufficiently lower than 1V.
Therefore, for the switch SW that is closed, the corresponding input ports K ₀ to K ₃ will surely become "L",
It is possible to accurately determine whether the switch SW connected to column line _Y1 is open or closed. Next, by outputting "H" to the output port _F1 to turn on the transistor _Tr2 , and similarly detecting the input voltages of the input ports _K0 to _K3 ,
It is possible to accurately determine whether the switch SW connected to column line _Y2 is open or closed.

Then, after determining the switch SW, step 3
As shown in the figure, the output ports S ₀ to S ₄ and
Output signals to F ₀ and F ₁ . In this case, the number of light emitting diodes L that are turned on increases, and the transistor
The saturation voltage between the collector and emitter of Tr ₁ and Tr ₂ is
Even if it exceeds 1V, there is no problem because it is after the switch SW has been determined to be open or closed.

In this way, while the light emitting diode L is turned off, the state of each switch SW is read, so the collector current of the scanning transistor Tr is only the amount due to the closed switch SW, and the current between the collector and emitter is The saturation voltage becomes sufficiently low and it is possible to accurately determine whether the switch SW is open or closed.

Above, one embodiment of the present invention has been described in detail.
It can be modified as appropriate within the scope of the gist of the present invention. For example, if PNP type transistors are used instead of NPN type transistors Tr ₁ and Tr ₂ , the logic of "H" and "L" that determine whether the switch SW is open or closed will be reversed, and each row line X ₁ to X ₄ will be pulled up. Instead of connecting to the power supply E with a resistor R, it is grounded with a pull-down resistor. Further, as the display device, devices other than light emitting diodes can be used. Furthermore, although a switch matrix with 4 rows and 2 columns is shown as a switch, the number of these and the number of indicators are arbitrary, and the present invention can be applied to switches other than the switch matrix.

[Effects of the invention] As detailed above, according to the invention, by turning off the display when dynamically scanning the switch, the switch can be opened and closed accurately without being affected by the display that is on. It is possible to provide a switch open/close determination device that can determine whether a switch is open or closed.

[Brief explanation of the drawing]

FIG. 1 is a flowchart showing one embodiment of the present invention, and FIG. 2 is a block diagram showing a general switch open/close determination device. 1...Microcomputer, SW...Switch, L...Light emitting diode (indicator), Tr ₁ , Tr ₂
...transistor.

Claims (1)

[Scope of utility model registration request] In a switch open/close determination device, a switch is connected to a transistor in which a plurality of indicators are connected in parallel, and a microcomputer dynamically scans the switch to determine whether the switch is open or closed. A device for determining whether a switch is open or closed, characterized by comprising means for turning off the switch.