JPH0425219A - Touch switch circuit - Google Patents

Abstract

PURPOSE:To prevent tentative stop due to noise or the like at the time of contacting by connecting a phase detector to the output of a NAND or AND gate, and operating a monostable multivibrator with the phase detector. CONSTITUTION:When a human body is in contact with a contact part 6, an input pulse to an input terminal 3a is delayed by a time T3 by a delay circuit comprising a resistor 4 and a combined capacitor consisting of the ground capacitance of the human body and a capacitor 7. When the delay time T3 is larger than a delay time T2, the pulse in a time width corresponding to the difference between the delay times T2, T3 is outputted from the output of an AND gate 3 at the tailing of the reference pulse output opposite to the time of non-contacting. Thus, a negative pulse with a time width corresponding to a time (T3-T2) is outputted from the NAND gate 8 of a phase detector to trigger a monostable multivibrator 9. Thus, the tentative stop due to noise at the contact is prevented.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a touch switch circuit that detects mechanical contact to a contact portion.

[Conventional technology]

In conventional touch switch circuits, a method of detecting the ground capacitance of a contact body is often used.

This is done by connecting the output from the pulse oscillator to both input terminals of a two-person gate such as an AND gate or exclusive OR gate, and further connecting a contact part to one of them.
This detects that the phase difference between two input terminals is small when they are not in contact, and increases due to the ground capacitance when they are in contact.

[Problem to be solved by the invention]

In the above method of determining the magnitude of the phase difference, it is necessary to determine the magnitude of the phase difference, which is a time period.The circuit becomes complicated, and the position during non-contact is affected by the environment in which it is used and variations in individual components. The phase difference is large, and as a result, the circuit may operate during non-contact. To prevent this, it is necessary to connect a delay circuit consisting of a resistor or a capacitor to the input terminal on the contact side. Further, there were also problems such as the operation temporarily stopping due to noise etc. upon contact.

[Means to solve the problem]

For this reason, the present invention connects a contact part and a reference pulse output to one input terminal of a NAND or an AND gate, connects an inverter gate between the other input terminal and the reference pulse output, and connects an inverter gate to the output of the NAND or an AND gate. An object of the present invention is to provide a touch switch circuit, which is characterized in that a phase detector is connected to the phase detector to operate a monostable multivibrator.

〔Example〕

An embodiment of the present invention will be explained with reference to FIGS. 1 and 2.

The square wave reference pulse output supplied from the inverter buffer (2) connected to the pulse oscillator (1) is connected to one input terminal (3a) of the AND gate (3) through a resistor (4).
), and is further inverted by an inverter gate (5) and connected to the other input terminal (3b).

The input terminal (3a) is touched by a human body and two contact portions (6) are connected via a capacitor (7). The output of the AND gate (3) is connected to the input terminal (8a) of the Nandt gate (8), which is a phase detector, and the other input terminal (8b)
The pulse output before inversion is connected to .

A trigger terminal (9a) of a retriggerable monostable multivibrator (9) is connected to the output terminal of the Nant gate (8).

The resistor (10) and capacitor (11) determine the operating time of the monostable multivibrator (9).

Next, the operation of this embodiment will be explained with reference to FIG. 2. Since the pulse oscillator (1) is always operating, it outputs rectangular pulses as shown in (,).

Therefore, as shown in (a), the reference pulse output from the inverter buffer (2) is inverted compared to (e), and its phase is delayed by the delay time T1 of the inverter buffer (2). This delay is about 30 ns in the case of a normal C-MOSIC. The reference pulse output mentioned above is a resistor (4
) is connected to the input terminal (3a) of the AND gate (3), and when there is no contact with one human body, this input pulse is (
As shown by the solid line in b), it has the same phase as the reference pulse output. Also, since it is connected to the other input terminal (3b) via the inverter gate (5), it is inverted and delayed by T2 compared to (b) as shown in (C). As a result, from the output of the AND gate (3), a pulse having a time corresponding to <72 is outputted at the rise of the reference pulse output, as shown by the solid line in (d). This output is connected to the input terminal (8a) of the Nandt gate (8) which is a phase detector, but as shown in (e), the pulse output before inversion connected to the other input terminal (8b) is at this time. Since is at a low level, the output of the Nant gate (8) maintains a high level as shown by the solid line in (f), and as a result, the monostable multivibrator (9) is not triggered, so its output is (g
) is maintained at a low level as shown by the solid line.

Next, when the human body touches the contact part (6), the input pulse to the input terminal (3a) is caused by the delay circuit formed by the combined capacitance of the ground capacitance and the capacitor (7) and the resistor (4). As shown by the broken line in (b), it is delayed by <73. If this delay time T3 is larger than the delay time T2,
From the output of the AND gate (3), a pulse with a time width corresponding to the difference between <73 and T2 as shown by the broken line in (d) is output at the falling edge of the reference pulse output, contrary to the non-contact time.

Therefore, from the Nandt gate (8), which is a phase detector, (f)
As shown by the broken line, a negative pulse with a time width corresponding to (T3-72) is generated, which triggers the monostable multivibrator (9).

While the human body is in contact with the contact part (6), the output of the monostable multivibrator (9) maintains a high level as shown by the broken line in (g), so this is amplified and used as a relay or motor. Can drive actuators.

Note that the monostable multivibrator does not need to be retriggerable; in that case, a stable output can be obtained by integrating the output of the monostable multivibrator. or,
It is also possible to connect a resistor or a variable resistor between the reference pulse output and the input terminal of the inverter gate, and further add delay time using a delay circuit constituted by this, the input capacitance of the input terminal, and an additional capacitor.

Furthermore, changing the AND gate to a Nand gate, or vice versa, can be freely done depending on circuit design requirements or the adoption of positive logic or negative logic.

〔Effect of the invention〕

As mentioned above, the present invention utilizes the delay time of the inverter gate connected to one of the input terminals of the AND gate, so it is compared to a delay circuit configured with a resistor or capacitor and using the delay time. The Nandt gate, which is a phase detector, is designed to prevent malfunctions during non-contact, and to ensure that the pulse output from the AND gate shifts from the rising edge of the reference pulse to the falling edge of the reference pulse when the human body is in non-contact and in contact. The operation is reliable. Furthermore, since a monostable multivibrator is used, temporary stoppage due to noise upon contact can be prevented by appropriately adjusting its operating time.

[Brief explanation of the drawing]

The drawings show an embodiment of the present invention, and FIG. 1 is a circuit diagram thereof;
FIG. 2 shows the operation, with the solid line showing the non-contact state and the broken line showing the contact state. In the figure, (2) is an inverter buffer that outputs a reference pulse, (3) is an AND gate, (5) is an inverter gate, (6) is a contact part, (8) is a Nandt gate that is a phase detector, (9) is a monostable multivibrator. Fig. Fig. Fig. + TI: 1 tg)

Claims (1)

[Claims] 1. A contact part and a reference pulse output are connected to one input terminal of a NAND or AND gate, an inverter gate is connected between the other input terminal and the reference pulse output, and an inverter gate is connected between the other input terminal and the reference pulse output. A touch switch circuit characterized in that a phase detector is connected to the output of the gate, and the phase detector operates a monostable multivibrator. 2. The touch switch circuit according to claim 1, wherein a NAND or an AND gate is used as the phase detector.