JPS6349917A - Circuit for recognizing opened/closed state of switch - Google Patents

Abstract

PURPOSE:To reduce the number of I/O lines by connecting a serial circuit of a diode orientated in a specific direction and an opening/closing switch in parallel between a 1st and a 2nd conductive lines. CONSTITUTION:A remote control device circuit A208 is controlled by three key switches S1-S3 in an remote control part 203. The remote control is constituted of a polarity control circuit 204, a current detecting circuit 205, a current supply circuit 206 and a control circuit 207. The two key switches S1, S2 of said remote control part 203 are formed by a serial circuit consisting of the 1st and the 2nd diodes D1, D2 which are respectively orientated in the reverse directions so that the current supply directions at the time of ON of the switches S1, S2 are distinguished. Thus, the opened/closed state of lines W1, W2 can be decided by a polarity discriminating circuit 204 or the like by selectively turning on/off respective key switches S1-S3. The existence of current is detected by a current detecting circuit 205 or the like and the opened/closed state of the switches S1-S3 is discriminated to control the circuit A208.

Description

Detailed Description of the Invention (a) Industrial Application Field The present invention relates to a switch open/close state recognition circuit. More specifically, it is a device that detects whether a plurality of switches for opening and closing electrical paths are in an open state or a closed state. This relates to a circuit that inputs information about the presence of a computer into an electronic circuit, such as a microprocessor.

(B) Conventional technology Generally, in order to make an electronic circuit recognize the open/closed state of a switch, a potential difference is applied to two wires connected to both ends of the switch, and some method is used to detect whether or not current flows between the two wires. If there are N switches, if you do this for each switch independently, 2N
However, if all the wires on one side of the switch are shared, only N+1 wires need to be connected to the electronic circuit to determine the status. As a method for further reducing the number, a method is often used in which a matrix is constructed between a tS group (G+) consisting of n2 electric wires and a layer wire group (G2) consisting of n electric wires. In this method, the number of wires required to recognize the states of n and nt switches can be reduced by arranging switches corresponding to n+n□ pairs of wire G1 and t gland G. n1+n! I'm trying to make sure that it's enough.

Now, signal input/output of a microprocessor or the like is normally performed through a terminal called a port.

When using boats built into the microprocessor, the number of boats is self-limited.

When externally attaching boats, a large number of boats can be provided, but as the number of boats increases, more parts must be used. Mochikai No. 58-106626 (GO6
F3102) is an example in which the input/output line to the switch is shared with the address line and the data line, thereby eliminating the need to use a port, but an address defood circuit is newly required.

When trying to make a microprocessor recognize the status of a large number of switches using conventional methods, the number of ports is often insufficient. there were. This situation is not limited to microprocessors, but is common in cases where the number of input/output lines is limited for some reason. Furthermore, even if the number of switches is not particularly large, when the switches and the circuit that recognizes their status are far apart, it is better to have fewer tSs connecting them. The problem is that there are too many.

(c) Problems to be solved by the invention The present invention can solve problems even if the number of input/output lines to an electronic circuit is small.
It is an object of the present invention to provide a circuit means that can recognize the open and closed states of many switches.

(d) Means for Solving the Problems The present invention provides a diode (a) that is connected in parallel between the first and second conductive wires (<W1) (Wj) and that allows current to flow only in the direction from W to W.
D2) and the open/close switch (S+), and (b) a diode (b) that allows current to flow only in the direction of W1 from w+.
Connect at least two circuits: a second series circuit consisting of D2) and the open/close switch (S2), and (C) a circuit consisting of the open/close switch (S2), and determine whether current can flow from Wl to W8. The gist of the present invention is to sequentially test whether a current can flow from Wl to W1, and determine whether the switch is open or closed based on the results.

(e) Operation and Examples The principle of the present invention will be explained with reference to FIG. 1, taking as an example the case where the circuits (a), (b), and (c) are all connected. Table 1 shows the electric wire W+ (Lot) to W,
(Whether the TL flow flows to 102> or not, and from W to Wl
The correspondence between the results of two types of continuity tests to determine whether current flows to or not and the open/close states of switches (S2), (S2), and (SS) is shown. There is no one-to-one correspondence between the eight open/close states of the switch and the continuity test results, but if it is guaranteed that at most one of the three switches is in the closed state, , columns (1) (2) (3) (4) of Table 1
), and it is possible to determine which switch is open based on the continuity test results. Table 1 shows the open/close states of the switches and the results of the continuity test.

Next, consider a case where any one of circuits <a), (b), and <c) is omitted. First, if (a) is omitted,
If it is assumed that Sl is always open, the column (
1)(2)<3)(5) is valid, and (S2)(S
2) are not closed at the same time, then column (1) (
2) See (3) and check S8 and S based on the continuity test results.

The status of can be determined. The same applies if (b) can be omitted. If (C> is omitted, the valid columns in Table 1 are (1), (3), (4), and (7)), and in this case,
Including the state where (Sl>, (S t) are closed at the same time,
There is a one-to-one correspondence between the state of the switch and the result of the continuity test.

As described above, in the present invention, two or three switches are arranged where conventionally one on-off switch is arranged, and conversely, the state of the same number of switches can be controlled by using fewer electric wires. Therefore, it can be determined through

FIG. 2 shows a remote control unit (203
) three key switches (S2), (Sffi), (
The remote control device circuit A(
208) is remotely controlled. In FIG. 2, the current supply circuit (206) has two lines (W +') (W f
This circuit applies a potential difference (fixed polarity) to fi') and supplies a current that flows when these two lines become a closed circuit. The current detection circuit (205) connects one of the two lines (W+'
), and by detecting whether or not current is flowing, it is determined whether or not the two lines are closed, and the information is transmitted to the control circuit (207). Polarity control circuit (20
4) is the above two lines (W l') (W !') and Wl
(201), W, and (202), and is a switch circuit that connects the two wires of (201), W, and (202).
, '-w2) (w, '-w2) or (W+' WJ
) (W-'-W1), the control circuit (207) sequentially inverts the connection combination of the polarity control circuit (204) using a logic circuit (microprocessor, etc.). , ′? The open/close states of the switches (S 2 ) (S 2 ) (S s ) are determined according to Table 1 based on the information received from the f-current galvanometer output circuit 05 >. Based on the judgment results, the circuit (
A) (208) is controlled. To explain in more detail, the current supplied from the current supply circuit (206) is connected to the polarity control circuit (206).
204>, the direction is reversed by ffi[I.

The control circuit (207) controls this switching timing, and at the same time controls (S2) (S2) (
The circuit A (20g) is controlled by determining the open/closed state of the circuit A (20g).

Note that in this embodiment, three switches (S2) (S2)
(S1) to control the operation of circuit A (208). For example, if we take a motor as circuit A,
Using a 2gJ conductor and three switches, you can remotely control the motor's 1 forward rotation, 1 reverse rotation, and 1 stop operation.

The $3 figure shows 12
This is a circuit that scans several key switches. micro·
The processor (305) is configured to perform a process such that boat<P I)(P t)
(p I) (P 2), (p2) (ps) and (
The input/output direction can be switched for each pair of P=>(P-). Each boat has a protective resistance (Rp+) (Rpm
) (Rp+) (Rpt)
, )<W)Cws>(w2) are connected to the power supply potential (logic high level) through pull-up resistors (R1) (R,>(R,)(R,), respectively.
W2) and (W2), (W1) and (W2), (W2) and (
A circuit similar to that shown in FIG. 1 is constructed between W2), (Wt), and (W4), respectively. Impedance Zout at output of each boat, impedance Zin at input
, and pull-up resistor (R,) (Rt) (Rs) (R,
) between the resistances (!(r)) of Zout (r (Zi
n... List items related to (1).

Protective resistance (Rp+ > (Rpa) (Rps) (Rp4)
prevents excessive current from flowing if, for example, the boat (P+) is outputting a high level and the boat (P2) is outputting a low level and switch (S2) and switch (S,2) are closed at the same time. This protective resistance (Rp, > (R
The resistance value (r2) of p□)(Rps)(Rpa) must be r, (r...(2)).

Table 2 is a table showing the procedure for controlling the state of the boat and the method for determining the open/closed state of the switch in the circuit of FIG.

The input/output direction and output level of each boat are controlled by software as shown in Table 2 (a).
For example, (1> in Table 2 (a) is boat (P 2) (
P *) is set to the output state and outputs low [L-O] and high [H-1] levels, respectively, and the level detected by the ports (P s) (P 2) in the input state at that time is set to Y.
This means that it is temporarily stored as s, , Y41. This cycle is repeated at appropriate time intervals, with the four states in Table 2 sequentially (the order does not matter). Furthermore, (Yij) means that the boat < Pj) is 0" output. represents the input level of the boat (Pi) at the time of .

By going through the states in Table 2 (a), ys+, Y4
1.Yl! , Y41, Y mouth, Yo, Y, ,, Y warehouse, 8
information can be obtained. From these, the closed switch is determined according to Table 2 (b). This determination is correct as long as there is at most one switch in the open state.As an example, the case where only the switch (S++) is closed will be explained in detail. In state (1) of Table 2 (a), the line (W2
) is at a higher potential than the Tt line (W1), but the rectifier (Dl
1), no current flows between them, and the boat (P
A high level potential is input to 3) via the pull-up resistor (R1) (ie, Y.-1).

Next, in state (3) of Table 2 (a), conversely, t
! The rectifier (D, 2) becomes conductive and the current flows from the power supply potential (Vcc) to the pull-up resistor (R1) and the rectifier (
Dl1), the switch (S, 1), and the protection resistor (Rps) to the boat (ps). In this case, the above formula (1)
Because of the relationship shown in equation (2), the potential of the electric wire (Wl> is almost the same as the output potential of the boat (P2) and becomes a low level (that is, Y+s"Q, where both ends of the rectifier in a conductive state (The potential difference is assumed to be sufficiently small.)

Therefore, from Table 2 (b), it is determined that the switch (S, 2) is in a conductive state (it is clear that all six input information except Y, 1, and Y11 are 1).

In practical use, by checking the status history from several cycles ago, it is possible to detect cases where one switch is closed while the second and subsequent switches are closed, or cases where 4 in Table 2 (a)
It is possible to reject cases where the open/closed state changes during a cycle of two states, or to eliminate chattering. These depend on the software.

Figure 4 shows the key switch scanning circuit of Figure 3 and Kawa-sama, but the difference is that the switch (S, , > (
There is no S Im) (S, 2) (S as), and the human output direction of the four boats (P, > (P1) (Ps) (P2) can all be switched independently.
Also, as a result, the protective resistance (Rpa) (Rps) (Rp
s>(Rpa) is also inconvenient. Although the number of switches in this circuit is 8, which is less than that in FIG. 3, it has the advantage of being able to accurately determine even when two or less switches are closed at the same time.

Table 3 is a table showing the procedure for controlling the state of the boat and the method for determining the open/closed state of the switch in the circuit of FIG.

Control follows Table 3 (a), and determination follows Table 3 (b). (b) is (y, , y, 2), (Y41, y, 2)
, (Y++, Y!s), (Yo, Y2), of which 2 are not (1, 1).
For example, (Y
13, Y □5) - (O, 0), (Y, , ,
Y14)-(o, 1), (Y, 1, Yes)-
(1, 1), (Y42, Y□) - (1, 1), from the table (S, 2), (S).

It can be determined that the three switches (S2) are closed, and
This set of Yij values cannot be created by the open/closed states of any other switches. In this example, it was determined that three switches were closed, but in general, a correct determination is always possible as long as two switches are closed.

Figures 3 and 4 are examples using four boats, but this can be easily expanded to include (n+10n+) boats, 3n+nx in Figure 3 and 2n in Figure 4.
1nt switches can be scanned (in the conventional method, nl
n).

(f) Effects of the Invention As described above, according to the present invention, the remote control control line, etc.
2 instead of the conventional 4 (in the case of 3 switches)
In addition, the number of input/output lines for key switch scanning can be reduced to 172 to 1/3 of the conventional number, which is effective in reducing hardware. This is particularly effective when scanning a keyboard with a single-chip type microprocessor or the like that has a limited number of input/output ports.

[Brief explanation of the drawing]

FIG. 1 is a circuit diagram for explaining the basic principle of the switch open/close state recognition circuit of the present invention, and FIG. 2 is a circuit diagram showing an embodiment in which the switch open/close state recognition circuit of the present invention is applied to a remote control device. , 3 and 4 are circuit diagrams showing an embodiment in which the open/close state recognition circuit of the present invention is applied to a key switch scanning circuit. (101) (201) (301) (401)... Conductive wire (W2), (102) (202) (302) (402
)... Conductive wire (W), (303) (403)...
Conductive wire (Wj), (304) (404)... Conductive wire (
W2), (203)...Remote control unit, (204)...
・Polarity control circuit, (205)...Current detection circuit, (2
06)... Current supply circuit, (207)... Control circuit, <208)... Remote control device circuit, (305) (4
05)...Microprocessor, (DI) (D *
)(p ++)(p liri(vt2)(p t2)(p
s2) (p s*) (p, 1) (D at)...
Guiodo, (s 2) (s 2) (s 5)
(s,2)(S,ri(S,j)(s,,>
(S11>(Sll>(Sj,>(S, ri(St2)(
S, > (8, 1) (S, 2)... Open/close switch.

Claims (3)

[Claims] (1) In parallel between the first and second conductive wires (W_1) (W_2), (a) a unidirectional conductive element (D_1) that allows current to flow only in the W_1 to W_2 direction and an open/close switch (S_1); 1st
a series circuit; (b) a second circuit consisting of a one-way conductive element (D_2) that allows current to flow only in the direction from W_2 to W_1 and an open/close switch (S_2);
When at least two circuits, a series circuit and (c) an on/off switch (S_3) are connected, and the potential of W_1 is set to be higher than W_2, the state of the current flowing between the two conductive wires, and W_
A switch open/close state recognition circuit that determines the state of the open/close switch based on the state of the current flowing between these conductive wires when W_2 is set to a higher potential than W_1. (2) The first and second conductive wires (W_1) (W_2) are n_
A claim that is one of n_1n_2 pairs formed by combining one conductive wire from a group of conductive wires (G_1) consisting of one conductive wire and a group of conductive wires (G_2) consisting of n_2 conductive wires. An open/close state recognition circuit for the switch according to item 1. (3) The state of the current flowing between the first and second conductive wires is such that when applying a potential difference between the two conductive wires, one conductive wire has a high impedance, and the other conductive wire has a low impedance. Claim No. 1, wherein when a potential is supplied to the two conductive wires and a current flows between the two conductive wires, the state of the current is detected by utilizing the fact that the potential of the conductive wire on the high impedance side is drawn into the potential on the low impedance side. An open/close state recognition circuit for the switch described in item 1 and item 2.