Capacitive proximity alarm circuit and system

• US 8,624,751 B2
• Filed: 07/20/2011
• Issued: 01/07/2014
• Est. Priority Date: 12/28/2010
• Status: Expired due to Fees

• Current Assignee: Hong Fu Jin Precision Industry (Shenzhen) Co., Ltd. (Hon Hai Precision Industry Co., Ltd.), Hon Hai Precision Industry Co., Ltd.
• Original Assignee: Hong Fu Jin Precision Industry (Shenzhen) Co., Ltd. (Hon Hai Precision Industry Co., Ltd.), Hon Hai Precision Industry Co., Ltd.
• Inventors: Xie, Ling-Yu, Xie, Xing-Ping
• Primary Examiner(s): Lee, Benjamin C
• Assistant Examiner(s): BURGDORF, STEPHEN R
• Application Number:
  US13/186,768
• Publication Number:
  US 20120161976A1
• Time in Patent Office: 902 Days
• Field of Search: 200/600, 307/116, 307/125, 307/652, 324/66, 324/658, 327/517, 340/562, 340/568.1, 340/573.1, 340/657, 340/666, 340/686.1, 340/686.6, 361/179, 361/181, 600/525
• US Class Current: 340/686.6
• CPC Class Codes: B25F 5/00 Details or components of portable power-driven tools not particularly related to the operations performed and not otherwise provided for
• CPC Class Codes: F16P 3/148 using capacitive technology

Abstract

An alarm system for emitting an alarm includes a distance detecting circuit, a gate circuit, a voltage conversion circuit, a distance judging circuit and an alarm circuit. The distance detecting circuit receives a first signal, detects a distance between an object and the alarm system, outputs a second signal and a third signal according to the distance. The gate circuit receives the second signal and the third signal and outputs a voltage level signal. The voltage conversion circuit receives the voltage level signal and converts the voltage level signal into a DC voltage signal. The distance judging circuit receives the DC voltage signal and compares the DC voltage signal against a reference voltage signal to output a control signal if necessary. The alarm circuit receives the control signal and produces the alarm when the distance between the object and the alarm system is less than a threshold distance.

Claims

1. An alarm system for alarming when a distance from an object is less than a threshold distance, comprising:

a signal generating circuit adapted to generate a first signal;

a distance detecting circuit adapted to receive the first signal, detect a distance between the object and the alarm system, output a second signal and a third signal according to the distance;

a gate circuit adapted to receive the second signal and the third signal and output a voltage level signal;

a voltage conversion circuit adapted to receive the voltage level signal and convert the voltage level signal to a DC voltage signal;

a distance judging circuit adapted to receive the DC voltage signal and compare the DC voltage signal with a reference voltage signal to output a control signal; and

an alarm circuit adapted to receive the control signal and produce an alarm when the distance between the object and the alarm system is less than the threshold distance,

wherein the signal generating circuit comprises a first operational amplifier, a crystal oscillator, a first resistor and a first capacitor;

the first operational amplifier comprises a first operational amplifier non-inverting input terminal, a first operational amplifier inverting input terminal and a first operational amplifier output terminal;

the first operational amplifier non-inverting input terminal is grounded via the first resistor;

the first operational amplifier inverting input terminal is grounded via the first capacitor; and

the first operational amplifier non-inverting input terminal is electrically connected to the first operational amplifier output terminal via the crystal oscillator;

the distance detecting circuit comprises a second operational amplifier, a metal slice, a second resistor and a second capacitor;

the second operational amplifier comprises a second operational amplifier non-inverting input terminal, a second operational amplifier inverting input terminal and a second operational amplifier output terminal;

the second capacitor comprises a second capacitor first terminal and a second capacitor second terminal;

the second operational amplifier non-inverting input terminal is electrically connected to the metal slice to detect the distance between the object and the alarm system;

the second operational amplifier non-inverting input terminal is electrically connected to the second capacitor first terminal via the second resistor; and

the second capacitor second terminal is grounded;

the distance detecting circuit further comprises a third operational amplifier;

a third resistor and a fourth resistor;

the third operational amplifier comprises a third operational amplifier non-inverting input terminal, a third operational amplifier inverting input terminal and a third operational amplifier output terminal;

the fourth resistor comprises a fourth resistor first terminal and a fourth resistor second terminal;

the third operational amplifier non-inverting input terminal is electrically connected to the fourth resistor first terminal via the third resistor;

the fourth resistor second terminal is electrically connected to a first connection point between the metal slice and the second resistor;

the third operational amplifier non-inverting input terminal is electrically connected to the first operational amplifier output terminal via the third resistor; and

the third operational amplifier inverting input terminal is electrically connected to the second operational amplifier inverting input terminal;

the gate circuit comprises an Exclusive OR logic chip;

the Exclusive OR logic chip comprises a first input terminal, a second input terminal and an Exclusive OR logic chip output terminal;

the first input terminal is electrically connected to the second operational amplifier output terminal; and

the second input terminal is electrically connected to the third operational amplifier output terminal;

the voltage conversion circuit comprises a fifth resistor and a third capacitor;

the fifth resistor comprises a fifth resistor first terminal and a fifth resistor second terminal;

the fifth resistor first terminal is electrically connected to the Exclusive OR logic chip output terminal; and

the fifth resistor second terminal is grounded via the third capacitor;

the distance judging circuit comprises a comparator and a variable resistor;

the comparator comprises a comparator non-inverting input terminal, a comparator inverting input terminal and a comparator output terminal;

the variable resistor comprises a variable resistor first terminal, a variable resistor second terminal and a variable resistor adjust terminal;

the comparator non-inverting input terminal is electrically connected to a second connection point between the fifth resistor and the third capacitor;

the comparator inverting input terminal is electrically connected to the variable resistor adjust terminal;

the variable resistor first terminal receives a first DC voltage;

the variable resistor second terminal is grounded; and

the comparator output terminal is adapted to output the control signal.

2. The alarm system of claim 1, wherein the first operational amplifier output terminal is adapted to output the first signal;

the second operational amplifier output terminal is adapted to output the second signal; and

the third operational amplifier output terminal is adapted to output the third signal.

3. The alarm system of claim 1, wherein the Exclusive OR logic chip output terminal is adapted to output the voltage level signal;

the second connection point between the fifth resistor and the third capacitor is adapted to output the DC voltage signal; and

the comparator output terminal is adapted to output the control signal.

4. The alarm system of claim 1, wherein the alarm circuit is adapted to emit light or make a sound to produce the alarm.

5. An alarm system for alarming when a distance from an object is less than a threshold distance, comprising:

a distance detecting circuit adapted to receive a first signal, detect a distance between the object and the alarm system, output a second signal and a third signal according to the distance;

a gate circuit adapted to receive the second signal and the third signal and output a voltage level signal;

a voltage conversion circuit adapted to receive the voltage level signal and convert the voltage level signal to a DC voltage signal;

a distance judging circuit adapted to receive the DC voltage signal and compare the DC voltage signal with a reference voltage signal to output a control signal;

an alarm circuit adapted to receive the control signal and produce an alarm when the distance between the object and the alarm system is less than the threshold distance; and

a signal generating circuit adapted to generate the first signal;

wherein the signal generating circuit comprises a first operational amplifier, a crystal oscillator, a first resistor and a first capacitor;

the first operational amplifier comprises a first operational amplifier non-inverting input terminal, a first operational amplifier inverting input terminal and a first operational amplifier output terminal;

the first operational amplifier non-inverting input terminal is grounded via the first resistor;

the first operational amplifier inverting input terminal is grounded via the first capacitor; and

the first operational amplifier non-inverting input terminal is electrically connected to the first operational amplifier output terminal via the crystal oscillator;

the distance detecting circuit comprises a second operational amplifier, a metal slice, a second resistor and a second capacitor;

the second operational amplifier comprises a second operational amplifier non-inverting input terminal, a second operational amplifier inverting input terminal and a second operational amplifier output terminal;

the second capacitor comprises a second capacitor first terminal and a second capacitor second terminal;

the second operational amplifier non-inverting input terminal is electrically connected to the metal slice to detect the distance between the object and the alarm system;

the second operational amplifier non-inverting input terminal is electrically connected to the second capacitor first terminal via the second resistor; and

the second capacitor second terminal is grounded;

the distance detecting circuit further comprises a third operational amplifier;

a third resistor and a fourth resistor;

the third operational amplifier comprises a third operational amplifier non-inverting input terminal, a third operational amplifier inverting input terminal and a third operational amplifier output terminal;

the fourth resistor comprises a fourth resistor first terminal and a fourth resistor second terminal;

the third operational amplifier non-inverting input terminal is electrically connected to the fourth resistor first terminal via the third resistor;

the fourth resistor second terminal is electrically connected to a first connection point between the metal slice and the second resistor;

the third operational amplifier non-inverting input terminal is electrically connected to the first operational amplifier output terminal via the third resistor; and

the third operational amplifier inverting input terminal is electrically connected to the second operational amplifier inverting input terminal;

the gate circuit comprises an Exclusive OR logic chip;

the Exclusive OR logic chip comprises a first input terminal, a second input terminal and an Exclusive OR logic chip output terminal;

the first input terminal is electrically connected to the second operational amplifier output terminal; and

the second input terminal is electrically connected to the third operational amplifier output terminal;

the voltage conversion circuit comprises a fifth resistor and a third capacitor;

the fifth resistor comprises a fifth resistor first terminal and a fifth resistor second terminal;

the fifth resistor first terminal is electrically connected to the Exclusive OR logic chip output terminal; and

the fifth resistor second terminal is grounded via the third capacitor;

the distance judging circuit comprises a comparator and a variable resistor;

the comparator comprises a comparator non-inverting input terminal, a comparator inverting input terminal and a comparator output terminal;

the variable resistor comprises a variable resistor first terminal, a variable resistor second terminal and a variable resistor adjust terminal;

the comparator non-inverting input terminal is electrically connected to a second connection point between the fifth resistor and the third capacitor;

the comparator inverting input terminal is electrically connected to the variable resistor adjust terminal;

the variable resistor first terminal receives a first DC voltage;

the variable resistor second terminal is grounded; and

the comparator output terminal is adapted to output the control signal.

6. The alarm system of claim 5, wherein the first operational amplifier output terminal is adapted to output the first signal;

the second operational amplifier output terminal is adapted to output the second signal; and

the third operational amplifier output terminal is adapted to output the third signal.

7. The alarm system of claim 5, wherein the Exclusive OR logic chip output terminal is adapted to output the voltage level signal;

the connection point between the fifth resistor and the third capacitor is adapted to output the DC voltage signal; and

the comparator output terminal is adapted to output the control signal.

8. The alarm system of claim 5, wherein the alarm circuit is adapted to emit light or make a sound to produce the alarm.