로그인회원등록 내글장바구니주문조회현재접속자
 상품 검색








 게시판 검색





 
 
회원등록 비번분실


온라인 입금계좌
ㆍ기업은행
ㆍ219-043192-01-028
ㆍ이건영

      거래은행 바로가기
 
 Sensor Applications
센서 자료실
작성자 leeky        
작성일 2006/04/06
첨부#2 touchsw1_block.gif (0KB) (Down:22)
Link#1 touchsw.html (Down:140)
ㆍ추천: 0  ㆍ조회: 524   
  Touch Sensitive Switch

Walter Banks, Byte Craft Limited

이 자료는 MPU의 포트만을 이용하여 하드웨어 추가없이,
절연체의 표면을 사람의 손이 접촉되었는지 검출하는 회로이다.
응용으로는 가전제품의 비접촉(무접점) 스위치 및 방수스위치 등의 응용이 가능하다.

A touch-sensitive switch is very easy to implement with a microprocessor.
The principle of the touch-sensitive switch is based on the rate of voltage rise on a capacitor
that is supplied with a constant current source.
When a constant current source is applied to a capacitor, the voltage will rise linearly with time.

The value of C is very low when the capacitor is a small plate on a printed circuit board.
The value of C rises significantly when a finger is pressed on the plate, separated by a thin layer of insulation material.
The number of free electrons in the finger acts like a virtual ground,
brought into close proximity to the insulated plate;
this effectively increases the value of the plate capacitance.

The touch-sensitive switch uses a port pin of a microcomputer to sense voltage on the capacitor.
Create a port-controlled constant current source with a series 500K resistor,
on a single port output pin. Toggling the pin between 0 and 1 will turn off and on the current source.
A current step function is applied to the capacitor,
and the capacitor voltage is measured after 5 microseconds.
 
If the capacitor voltage is higher than the trip voltage on the port,
then the capacitor value is low and no finger press is detected.
If the voltage has not risen to the trip point on the port,
then the capacitor value is high and a finger press is detected.

The following is a practical example of a touch sensitive switch:
 

The basic construction of the touch switch is a printed circuit pad overlaid
with a thin layer of insulating material. Heat shrink plastic can be used.

A port Pa puts out a step from 0 to Vcc through a 0.5M resistor (470K or 560K);
5 microseconds later, the port at Pb samples the value on the touch plate
(which is insulated from the finger). A sampled 1 indicates nothing touching the plate.
A sampled 0 indicates that the capacitor has not charged up to the switching threshold of Pb.

I have used these in a variety of ways, usually etching the plate directly
on a PC board and using a heat shrink plastic as an insulator.

The following code fragment illustrates the programming approach.
The function touch_switch_init is used to initialize the microprocessor's ports.
The function touch_switch is called whenever the status of the touch switch needs to be determined:
 touch_switch returns a 0 if the switch is not touched, and a 1 if it is being pressed.

void touch_switch_init (void)
{
/* Set port a to output and
port b to input */
pa_direction = output;
pb_direction = input;
}

char touch_switch (void)
{
pa.0 = 0; // Discharge the pin
delay_Ms(1); // Wait
pa.0 = 1; // Turn on the Constant current source
delay_Us(5); // Wait for 5 u_seconds
if (pb.0 == 1)
return (0); // No touch detected
else
return (1); // Touch detected
}


In simple applications where you need only one or two switches, the following circuit will also work.
 

This requires a single port bit, that outputs a 0 and discharges the capacitive switch.
The port data direction is changed and sampled 5 microseconds later.
A 0 indicates the presence of a finger, and a 1 the absence of a finger.
Use the following code fragment with this circuit.

char touch_switch (void)
{
pb_direction = output;
pb.0 = 0; // Discharge the pin
delay_Ms(1); // Wait
pb_direction = input; // Turn on the Constant current source
delay_Us(5); // Wait for 5 u_seconds
if (pb.0 == 1)
return (0); // No touch detected
else
return (1); // Touch detected
}

   
윗글 Digital Radar Speedometer
아래글 Economy radar detector
    N         제목    글쓴이 작성일 조회 추천
74 AT89C2051과 EM4095를 사용한 RFID 장치의 제작 leeky 2006/12/31 (일) 1172 0
73 UserPort for Windows 2000 leeky 2007/11/12 (월) 792 0
72 아날로그 PID 제어 회로 leeky 2007/11/12 (월) 1378 0
71 Windows Scope 2K4 leeky 2007/11/12 (월) 912 0
70 12C508 금속검출기 leeky 2006/02/24 (금) 1085 0
69 16C84 LCD표시 L,C 메터 leeky 2006/02/25 (토) 1129 2
68 89C2051 LCD표시 LC메터의 제작 leeky 2006/02/14 (화) 1143 8
67 12C508A 초음파 거리 측정기 avrtools 2006/02/23 (목) 1040 0
66 Caliper to computer (RS-232) interface leeky 2006/02/23 (목) 1052 4
65 가속도센서 ADXL202의 PIC12C508 인터페이스 leeky 2006/02/20 (월) 1018 2
64 16F84 광학식 심박측정기 leeky 2006/02/27 (월) 1102 6
63 12C508 전자 나침판 leeky 2006/02/27 (월) 689 0
62 ENC28J60 Ethernet to SPI Header Board leeky 2007/03/26 (월) 961 0
61 SHT11 습도센서 8051 인터페이스 leeky 2006/02/14 (화) 1011 0
60 SHT11 습도센서 SX18 인터페이스 leeky 2006/03/16 (목) 638 2
59 SRF04 초음파 거리센서의 제작 leeky 2006/02/25 (토) 642 0
58 Ambient Light Sensors TSL2550 avrtools 2006/04/06 (목) 453 0
57 PIC16F877A BioSense Physiologic Sensing leeky 2006/04/06 (목) 587 0
56 Electrocardiogram (ECG) Front End leeky 2006/04/06 (목) 664 0
55 Biometric Interface Board leeky 2006/04/06 (목) 774 0
54 MAX2242 802.11b 블루투스 RF증폭기 leeky 2006/04/06 (목) 464 0
53 AX.25 9600BPS 무선모뎀 L2PCX leeky 2006/04/06 (목) 363 0
52 TCS230 색상검출 평가키트 leeky 2006/04/06 (목) 618 0
51 100V10A 50W 전자부하 leeky 2006/04/06 (목) 542 0
50 FLAME SENSOR UVTRON R2868 leeky 2006/04/06 (목) 547 0
49 Compact Optical Image Scanner leeky 2006/04/06 (목) 481 0
48 지자기 방위계 모듈 CMPS03 leeky 2006/04/06 (목) 611 0
47 0~1.5KV 정전기 측정센서 PKE05A1 leeky 2006/04/06 (목) 326 0
46 Rain Sensor 인터페이스 회로 leeky 2006/04/06 (목) 550 0
45 초음파 감지 센서 leeky 2006/04/06 (목) 535 0
44 HUMIDITY SENSOR HS-1100 leeky 2006/04/06 (목) 415 0
43 Relative Humidity Sensor KSH01, KSH-02 leeky 2006/04/06 (목) 312 0
42 Digital Radar Speedometer leeky 2006/04/06 (목) 472 0
41 Touch Sensitive Switch leeky 2006/04/06 (목) 524 0
40 Economy radar detector leeky 2006/04/06 (목) 359 0
39 Twin Loop metal detector leeky 2006/04/06 (목) 489 0
38 Proximity Detector CS209A/D leeky 2006/04/06 (목) 468 0
37 Lego Sound Sensor leeky 2006/04/06 (목) 428 0
36 12C508 IR Proximity Detector leeky 2006/04/06 (목) 630 0
35 Sharp IR Sensor Hack leeky 2006/04/06 (목) 613 0
34 TIL300 PRECISION LINEAR OPTOCOUPLER leeky 2006/04/06 (목) 375 0
33 Analog Opto Isolator leeky 2006/04/06 (목) 421 0
32 Rich Caudle's capaciflector leeky 2006/04/06 (목) 264 0
31 Geiger Tube leeky 2006/04/06 (목) 376 0
30 Lynxmotion Infrared Proximity Detector leeky 2006/04/06 (목) 352 0
29 Low Power LED Flasher leeky 2006/04/06 (목) 424 0
28 백색 LED BLU 구동회로 leeky 2006/04/06 (목) 459 0
27 저전압 백색 LED 구동회로 leeky 2006/04/06 (목) 499 0
26 IR LED 송신회로 avrtools 2006/04/06 (목) 477 0
25 LED 총방사 광량의 측정 leeky 2006/04/06 (목) 392 0
24 자외선 측정센서의 교정 leeky 2006/04/06 (목) 341 0
23 UV센서 S9050의 데이터 leeky 2006/04/06 (목) 256 0
22 디지털 자외선 메터 leeky 2006/04/06 (목) 308 0
21 Simple Metal Detector leeky 2006/04/06 (목) 500 0
20 DS1820 온도센서 읽기 leeky 2006/04/04 (화) 554 0
19 RC5 적외선 리모콘의 신호처리 leeky 2006/02/17 (금) 649 0
18 NEC 적외선 리모콘의 전송규격 leeky 2006/02/17 (금) 538 0
17 MBI-6001 TRANSLESS LED DRIVER leeky 2006/02/14 (화) 377 0
16 PC로 제어하는 AD9850 DDS 신호발생기 leeky 2006/02/14 (화) 412 0
15 2400 Mhz test oscillator leeky 2006/02/14 (화) 445 0
14 DC BRUSHLESS FANS leeky 2006/02/14 (화) 533 0
13 RF mW Meter for SHF (2300MHz) leeky 2006/02/14 (화) 363 0
12 FET로 만드는 400W SSR leeky 2006/02/14 (화) 591 0
11 Scope2k4 소프트웨어 및 하드웨어 회로 leeky 2006/02/14 (화) 707 0
10 LTC1298를 사용한 PC 병렬포트용 ADC leeky 2006/02/14 (화) 369 0
9 0~14V 가변정전압, 0~2A 가변정전류 전원 avrtools 2006/02/14 (화) 506 0
8 ATV 1240-1300MHz 튜너용 PLL leeky 2006/02/14 (화) 257 0
7 1 Transistor FM Microphone leeky 2006/02/14 (화) 314 0
6 Helical Antenna Design Software leeky 2006/02/13 (월) 413 0
5 IRF510을 사용한 7MHz 출력10W 증폭기, PLL leeky 2006/02/13 (월) 463 0
4 MC34063A 설계용 계산기 avrtools 2006/02/13 (월) 447 0
3 RS232 신호 변환회로 leeky 2006/02/13 (월) 584 0
2 Sound card based multimeter Scope leeky 2006/02/13 (월) 731 0
1 2400MHz Helical Antenna Design leeky 2006/02/08 (수) 361 0
1

바구니 : 0
 보관함 : 0
오늘뷰 : 0
HOME   |   회사소개   |   제휴안내   |   회사위치   |   서비스이용 약관   |   개인정보 보호정책   |   사이트맵
17015 경기도 용인시 기흥구 동백중앙로16번길 16-25, 508호. 전화 : 031-282-3310
사업자 등록번호 : 697-47-00075 / 대표 : 이건영 / 업태 : 제조업 / 종목 : LED조명, LED전원, 제어장치.
개인정보 관리책임자 : 홈페이지 관리자 . Copyright ⓒ2016 아크레즈 (ACLEDS INC.)
HOME TOP PREVNEXT 0 0 0