JPH0581735U - Switch input reading device - Google Patents

Abstract

(57) [Abstract] [Purpose] A single port and input processing circuit process multiple switch inputs. [Structure] Resistors R _{11 to} R ₁₃ having different resistance values are respectively connected in series with switches 1 to 3 to form a switch circuit,
The terminal voltage of the switch circuit based on the combined resistance of the switch circuit and the resistor R ₁₄ connected in series is A / D converted (step 1) and compared with a plurality of threshold values stored in advance in the CPU 4 (step 2, 4 and 6) Determine the disconnection / contact state of each switch 1-3.

Description

[Detailed description of the device]

[0001]

[Industrial applications]

 The present invention relates to a switch input reading device having a plurality of switches, and more particularly to a technique for reducing the circuit configuration of a switch input processing circuit.

[0002]

[Prior Art]

 Conventionally, for example, an automobile has a plurality of switches such as an A / C (air conditioner) switch, a heater fan switch, and a rear defogger switch. When each switch is operated, the switch is in a disconnection / contact state, that is, an on / off state. The device that corresponds to the switch that is turned on is operated by determining the off state.

FIG. 5 shows a switch input reading device provided with such a plurality of switches. In FIG. 5, for example, three switches 1 to 3 are, for example, A / C (air conditioner), heater fan, and rear defogger switches. .. The resistor R ₁ and the capacitor C ₁ form a low pass filter that blocks high frequency noise generated when the switch 1 is turned on and off, and the diodes D ₁ and D ₂ are surge protection diodes for the switch 1. The inverter 5 also inverts the signal level from the switch 1 to the CPU 4. The switches 2 and 3 have the same circuit configuration. The CPU 4 has an input port corresponding to each switch, detects the signal level of the signal input from each switch through the low pass filter and the inverter, and determines the on / off state of each switch 1 to 3. To do.

[0004]

[Problems to be solved by the device]

 By the way, in the conventional switch reading device, the input port of the CPU 4 and its input processing circuit are required for each of the three switches 1 to 3, and the circuit is inevitably complicated. The present invention has been made in view of such conventional problems, and an object thereof is to provide a switch input reading device capable of processing a plurality of switch inputs with one port and an input processing circuit.

[0005]

[Means for Solving the Problems]

 Therefore, according to the present invention, as shown in FIG. 1, in a switch input reading device that determines the disconnection / connection state of each of a plurality of switches, resistors having different resistance values are connected in series to each of the plurality of switches. The series circuit of the switch and the resistor are connected in parallel to each other to form a switch circuit, and the switch circuit and another resistor are connected in series to connect to the power source, while the terminal of the switch circuit is connected. A voltage detecting means for detecting a voltage, and a judging means for comparing the terminal voltage detected by the voltage detecting means with a plurality of threshold values stored in advance to judge an open / closed state of each switch. I chose

[0006]

[Action]

 According to the above configuration, when the switches are connected, a combined resistance is formed by the resistance in series with the switch in the contact state and another resistance. Since the resistance values of the resistors connected in series with the respective switches are different from each other, the terminal voltage of the switch circuit differs depending on the disconnection / connection state of each switch. Therefore, this terminal voltage is detected by the voltage detecting means, and the judging means compares it with a plurality of threshold values stored in advance to judge the disconnection / contact state of each switch even if there is only one input processing circuit. Is possible.

[0007]

【Example】

 An embodiment of the present invention will be described below with reference to FIGS. The same elements as those in FIG. 5 are designated by the same reference numerals and the description thereof will be omitted. In FIG. 2 showing the present embodiment, the resistance R₁₁, R₁₂, R₁₃Are connected in series with, for example, the A / C switch 1, the heater fan switch 2, and the rear defogger switch 3, and the series circuit of each switch and the resistor is connected in parallel with each other to form a switch circuit. One end of this switch circuit is connected to the ground, and the other end is connected to the input terminal of the control unit 11. Also, each resistor R of the switch circuit₁₁, R₁₂, R ₁₃ Have different resistance values, for example R₁₁> R₁₂> R₁₃Set to. Resistance R in control unit 11₁₄Is another resistor connected in series with the switch circuit via the terminal of the control unit 11, and the voltage V_BConnected to the power supply. This resistance R₁₁~ R₁₃Combined resistance value R_totalIs calculated according to the equation (1), and the terminal voltage V of the switch circuit is_XIs calculated according to equation (2).

[0008]

[Equation 1]

Here, for example, the combined resistance value R when all the switches 1 to 3 are turned on_totalIs 1 / R ₁₁ ≠ 0, 1 / R₁₂≠ 0, 1 / R₁₃It is a value that ≠ 0, and when only switch 1 is turned on, 1 / R₁₁≠ 0, 1 / R₁₂= 0, 1 / R₁₃= 0. Resistance R in control unit 11₁₅Is a current limiting resistor, and the operational amplifier 12 constitutes a voltage follower for increasing the input impedance from the switch circuit to the CPU 4. Also the diode D₁₁And D₁₂, D₁₁And D₁₃, Are surge protection diodes.

The CPU 4 has one port for signal detection and has an A / D converter inside. And resistance R₁₄, A / D conversion is performed by inputting the terminal voltage of the switch circuit via the operational amplifier 12. In addition, as shown in FIG._s1, V_s2, ..., V_s8Is stored in advance. This threshold V_s1Is the threshold for judgment when all the switches 1 to 3 are turned on (connected), V_s2Is a threshold for determination when the switches 2 and 3 are turned on, V_s8Is a threshold for determination when the switch 1 is turned on, and each threshold V_s1~ V _s8 Is the terminal voltage of the switch circuit when all the switches 1 to 3 are turned on.₁, The terminal voltage when switches 2 and 3 are turned on is V₂, ..., the terminal voltage when the switch 1 is turned on is V₈As V₁<V_s1≤V₂<V_s2≤ ... ≤V₈<V_s8It is set so that In addition, the terminal voltage of the switch circuit calculated based on equation (2) is the power supply voltage V_B, An error occurs due to an error in the resistance value, etc._s1~ V_s8Is set so that the on / off state (disconnected / contact state) of each of the switches 1 to 3 can be reliably determined in consideration of this error.

The CPU 4 compares the voltage V _{IN of} the signal input through the operational amplifier 12 with the threshold voltage V _{s1 to} V _s8 , which is the terminal voltage of the switch circuit, by switching the switches 1 to 3 respectively. The on / off state of is determined. This determination processing is performed based on the flowchart of FIG. Next, this determination process will be described.

In step (denoted as “S” in the drawing, the same applies hereinafter) 1, the voltage V _IN input via the resistor R ₁₅ and the operational amplifier 12 is A / D converted. When all the switches 1 to 3 are turned on, it is determined in step 1 that V _IN ≤V _s1 and the process proceeds to step 3, where the devices corresponding to the switches 1 to 3 are A / C (air conditioner), heater fan, rear defogger. Operate all electrical loads in.

When the switches 2 and 3 are turned on, it is determined in step 4 that V _s1 ≦ V _IN <V _s2, and the process proceeds to step 5, where the electric load of the heater fan and the rear defogger corresponding to each of the switches 2 and 3 is increased. Operate. When all the switches 1 to 3 are turned off, it is determined in step 8 that V _{s8 ≤V IN,} and the process proceeds to step 10 to turn off all the electric loads of the A / C (air conditioner), the heater fan and the rear defogger.

The step 1 corresponds to the voltage detecting means, and the steps 2, 4, and 6 correspond to the determining means. According to this configuration, the combined resistance values of the resistors R _{11 to} R ₁₃ and the other resistor R ₁₄ of the switch circuit differ depending on the disconnection / contact state of each of the switches 1 to 3, and therefore the switch based on this combined resistance. The terminal voltage of the circuit is A / D converted and compared with a plurality of threshold values stored in advance in the CPU 4 to determine the disconnection / connection state of each of the switches 1 to 3 with one input circuit and one input port of the CPU. It is possible to reduce the number of input processing circuits.

[0015]

[Effect of the device]

 As described above, according to the present invention, a combined resistance of a switch circuit in which resistors having different resistance values are connected in series with a plurality of switches and another resistance connected in series with the switch circuit is Since it depends on the disconnection / connection state, the terminal voltage of the switch circuit based on this combined resistance is compared with multiple pre-stored threshold values to determine the disconnection / connection state of each switch with one signal input. It is possible to reduce the number of input processing circuits.

[Brief description of drawings]

FIG. 1 is a block diagram showing the configuration of the present invention.

FIG. 2 is a circuit diagram showing an embodiment of the present invention.

FIG. 3 is an explanatory diagram of thresholds stored in the CPU of FIG.

FIG. 4 is a flowchart showing the determination processing of FIG.

FIG. 5 is a conventional circuit diagram.

[Explanation of symbols]

1 to 3 switches 4 CPU R _{11 to} R ₁₅ resistance

Claims (1)

[Scope of utility model registration request] 1. A switch input reading device for determining the disconnection / contact state of each of a plurality of switches, wherein resistors having different resistance values are connected in series to each of the plurality of switches, and the switch and the resistor are connected in series. Circuit connected in parallel to each other to form a switch circuit, the switch circuit and another resistor are connected in series and connected to a power source, and a voltage detection means for detecting a terminal voltage of the switch circuit; A switch input reading device comprising: a determination unit that compares the terminal voltage detected by the detection unit with a plurality of threshold values stored in advance to determine the disconnection / contact state of each switch.