CN201577081U

CN201577081U - Capacitive touch induction key circuit

Info

Publication number: CN201577081U
Application number: CN 200920317885
Authority: CN
Inventors: 姚国祥; 张银波
Original assignee: NINGBO SHUNYUN ELECTRONIC CO Ltd
Current assignee: NINGBO SHUNYUN ELECTRONIC CO Ltd
Priority date: 2009-12-18
Filing date: 2009-12-18
Publication date: 2010-09-08
Anticipated expiration: 2019-12-18

Abstract

The utility model discloses a capacitive touch induction key circuit used in an electronic switch. The existing touch induction key circuit has complex design and high cost, and is easily disturbed by other signals on a circuit board to cause failure of a key, or is easy to produce mis-operation in anti-jamming test due to ideal design. The circuit is characterized in that an integrated circuit is a single chip; the integrated circuit is provided with a PWM port and an A/D port; a coupling capacitor and a current-limiting resistor are connected between the PWM port and an induction spring; an RC filter circuit is connected between the induction spring and the A/D port; and the induction spring is also connected with a grounded diode. The circuit has high reliability, can effectively work under the condition that the voltage of a power grid fluctuates in +/-15 percent, and has the advantages of simplicity, low cost, capability of generating certain economic benefit, low power consumption and energy conservation.

Description

A kind of capacitance touch induced key circuit

Technical field

The utility model relates to a kind of capacitance touch induced key circuit that is used for electronic switch.

Background technology

Electronic switch is one of core of electronic product, and the button indispensable part that is electronic switch.At present, the touch-induction-type button has become the indispensable part of household appliances product.Whether the variation that produces capacitance when the touch-induction-type button mainly utilizes the finger touch button is responded to has button to press, have reaction speed fast, save the space, be easy to advantage such as interchange.Though the touch-induction-type button have traditional mechanical formula button can not and advantage, but still can't replace the mechanical type button fully, reason mainly is complex circuit designs, the cost height of touch-induction-type button, and the touch-induction-type key circuit is subjected to the interference of other signals on the circuit board easily and causes button ineffective, perhaps because the undesirable of design is easy to generate misoperation in anti-interference test.

The utility model content

Technical problem to be solved in the utility model is to overcome the defective that above-mentioned prior art exists, and provides that a kind of circuit is simple, the capacitance touch induced key circuit of the high and low cost of reliability.

For this reason, the technical solution adopted in the utility model is as follows: a kind of capacitance touch induced key circuit, comprise integrated circuit, it is characterized in that described integrated circuit is a single-chip microcomputer, integrated circuit has PWM port and A/D port, a PWM port and an induction are connected a coupling capacitance and a current-limiting resistance between the spring, between induction spring and the A/D port RC filter circuit are arranged, and respond to the diode that spring also connects a ground connection.Current-limiting resistance is used to limit the discharging current of coupling capacitance, prevents that integrated circuit from damaging because of overcurrent.What integrated circuit adopted is single-chip microcomputer, and the power consumption of circuit is little, the reliability height.The PWM port is used to provide the pulse signal of a 223KHz, and the A/D port is used to detect the variation of magnitude of voltage.Because the resistance of resistance is much larger than the resistance of current-limiting resistance in the RC filter circuit, charge constant is much smaller than discharge time constant.

Pulse signal about the utility model 223KHz of PWM port output by integrated circuit, utilize the reverse characteristic of diode and different resistance values to discharge and recharge the time difference and obtain a magnitude of voltage through the RC filter circuit again, judge by the variation of this magnitude of voltage whether button is pressed.

Above-mentioned capacitance touch induced key circuit, the RC filter circuit comprises a filter capacitor and a filter resistance, filter capacitor ground connection, one end of filter resistance is connected with the induction spring, the other end is connected with the A/D port, connect between filter resistance and the A/D port a described filter capacitor and an earth resistance.

The utlity model has following beneficial effect:

1, circuit reliability can be high, under the situation of line voltage with ± 15% fluctuation, still can effectively work;

2, circuit is simple, and it is made of resistance, electric capacity and diode, does not have other integrated circuit except that single-chip microcomputer, and cost is low, can produce the certain economic effect;

3, low-power consumption, energy-conservation.

Below in conjunction with specification drawings and specific embodiments the utility model is further described.

Description of drawings

Fig. 1 is circuit theory diagrams of the present utility model.

The resistance of resistance R 1 is that the resistance of 1K Ω, R2 is that the resistance of 220K Ω, R3 is 2.2M Ω among Fig. 1, and the capacity of capacitor C 1 is that the capacity of 12pF, C2 is 0.1uF, and the model of diode D1 is 1N4148, and K1 is the induction spring.

Embodiment

Capacitance touch induced key circuit as shown in Figure 1, this circuit is controlled by two one-chip machine ports, and one is the PWM port, and one is the A/D port, and the PWM port is used to provide the pulse signal of a 223KHz, and the A/D port is used to detect the variation of magnitude of voltage.Be connected to coupling capacitance C1 and current-limiting resistance R1 between PWM port and the induction spring K1, between induction spring and the A/D port RC filter circuit arranged, induction spring K1 also connects the diode of a ground connection.The RC filter circuit is made up of filter capacitor C2 and filter resistance R2, filter capacitor C2 ground connection, and the end of filter resistance R2 is connected with induction spring K1, and the other end is connected with the A/D port, series filtering capacitor C 2 and earth resistance R3 between filter resistance R2 and the A/D port.

The course of work of the present utility model is as follows: the PWM port of integrated circuit (single-chip microcomputer) is exported the pulse signal that an amplitude is 5V, and when being in high level, pulse signal is by 1 charging of 1 pair of capacitor C of resistance R, charge constant T1=R1*C1; When being in low level, capacitor C 1 is by R2, R3 discharge, discharge time constant T2=(R2+R3) * C1; Because R2+R3＞＞R1, so the charging interval＜＜the discharge constant, that is to say that when electric capacity did not also have enough time to have put electricity, charging began again, so the output voltage after the process C1 is the direct voltage that an amplitude is about 800mV (charging interval is shorter).

When with finger touch induction spring, can change the equivalent capacity between induction spring and the ground, its capacity is increased, also quite be connected the bigger equivalent capacity of a capacity responding between pogo pin end and the ground; At this moment, circuit will charge to this electric capacity, and discharge is by diode D1 discharge because the bigger cause of capacitance, make charge constant T3＞＞T1, therefore can obtain the direct voltage that an amplitude is 2.26V.

From the above, when not having the touch sensible spring, the detected voltage of A/D port is 800mV; When with finger touch induction spring, the detected voltage of A/D port is 2.26V; Therefore, single-chip microcomputer can determine according to the variation of this magnitude of voltage before and after touching whether button is touched.

Claims

1. capacitance touch induced key circuit, comprise integrated circuit, it is characterized in that described integrated circuit is a single-chip microcomputer, integrated circuit has PWM port and A/D port, a PWM port and an induction are connected a coupling capacitance and a current-limiting resistance between the spring, be connected to a RC filter circuit between induction spring and the A/D port, the induction spring also connects the diode of a ground connection.

2. capacitance touch induced key circuit according to claim 1, it is characterized in that described RC filter circuit comprises a filter capacitor and a filter resistance, filter capacitor ground connection, one end of filter resistance is connected with the induction spring, the other end is connected with the A/D port, connect between filter resistance and the A/D port a described filter capacitor and an earth resistance.