sensor - York Jong on Diigo

08 Aug 09

28 Apr 09

偶得一触摸按键电路，请大虾分析其原理（附图） (www.ouravr.com)

www.ouravr.com/...bbs_content.jsp - Preview

A点输出高频脉冲信号幅度为5v，当没触摸时，信号没旁路，所以输出5v左右，当触摸时信号被旁路，幅度降低。芯片普通的单片机
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- A点为脉冲信号且一直保持不变，频率为350KHz,占空比约2/3，幅值为5V。但B点波形在触摸时是有变化，可似乎很难准确用视波器量出来

12 Feb 09

ADC without ADC

Some Microcontrollers, like the small 8-pin Microchip PIC 12F675, do have an ADC integrated, but it is expensier than a PIC without ADC. A simple solution is to use a RC circuit to measure the resistance or capacitance.

www.josepino.com/pic_projects - Preview

schematics embedded ADC sensor RC GPIO

The circuit labeled A shows the most common RC circuit used. I like to use the B circuit, I get better results.
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- You can replace the resistor and use a thermistor to measure temperature (PTC or NTC), also a photoresistor can be used to measure light. Any kind of resistive sensor can replace the resistor. If you are using a capacitive sensor, just replace the capacitor instead of the resistor.
- Just connect the RC circuit directly to an I/O pin of the microcontroller. You can use a 33pf capacitor and 1k resistor.
  
  First, make the I/O pin as OUTPUT.
  Second, make the pin POSITIVE (+) for one milisecond. (Using a PIC at 4mhz, a 255-cycles loop will be enough).
  Third, Make the I/O pin as INPUT and measure how long stays as POSITIVE (+).
- The PIC will measure the RC value of the I/O pin. If the time measured is too long, that means; there is no key pressed. Precision resistors and Mylar capacitor is required to get exact values.
- Note: Measuring capacitance or resistance usign this technique is affected by the voltage.

07 Feb 09

Bayer filter - Wikipedia, the free encyclopedia

A Bayer filter mosaic is a color filter array (CFA) for arranging RGB color filters on a square grid of photosensors.

en.wikipedia.org/...Bayer_filter - Preview

sensor color camera photo

06 Feb 09

ATMEL 业界最强电容触摸技术 Atmel Touch Library

www.ouravr.com/...bbs_content.jsp - Preview

touch sensor QTouch QMatrix AVR

05 Feb 09

Atmel Products - Touch Technology - Touch Library

Atmel Touch Library is a royalty free software library (IAR) for developing touch applications on standard Atmel AVR microcontrollers. Customers can link the library into their firmware in order to provide touch sensing capability to their projects. The Library can be used to develop single chip solution for many control applications, or to reduce chip count in more complex applications.

www.atmel.com/...touchswlib.asp - Preview

sensor touch QTouch QMatrix AVR

06 Jan 09

電容式觸控技術百家爭鳴

觸控面板(Touch Panel)與觸控按鍵(Touch Pad)一直都廣泛應用在售票機、銀行自動提款機(ATM)、筆記型電腦與各種攜帶式電子裝置上。其實，觸控感測器相當於傳統的機械式切換器 (Switch)，然因控制器單元的製作成本過高，難以普及，因此以往觸控按鍵大多使用具備接點的傳統機械式切換器較為可行

www.2cm.com.tw/technologyshow_content.asp - Preview

touch sensor screen

在上下玻璃基板表面內側，鋪設條紋狀方向呈90°的交錯電極膜片
上方基板為樹脂膜片，可以直接黏貼在顯示器表面。而膜片之間設有隔板(Separator)，未觸控時膜片之間維持一定間隙，並保持絕緣狀態，一旦手指觸壓膜片時，該部位會變形，導致電極相互接觸、電流導通，此時只要感測已導通的對線(Pair)，就可以獲得交點的座標
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- 四線式觸控面板的結構單純，但缺點是穿透率不利於廠商，且膜片端的電極一旦受損，面板容易發生故障，導致使用壽命過短
- 五線式則是四線式的改良版。如圖2所示，它是全面製作透明電極，再從玻璃端的四個角落與膜片端處拉出電線，合計5條線因而稱為五線式。其運作方式是在觸控時，電壓會施加至左右方向的電極之間，膜片的電壓隨著觸控位置改變，如右側施加+5伏特，左側施加-5伏特時，一旦觸控中央部位，膜片的電壓就變成2.5伏特，隨著手指移動至右側就接近5伏特、移動至左側就接近0伏特
- 五線式觸控面板整面都是透明電極，因此抗損性很高，使用壽命也較長
- 縱橫鋪設電極與四線阻抗膜方式相同，不過投射電容方式的阻抗膜卻不是通過觸控領域，而是捕捉電極之間的電容變化
- 面板表面覆蓋玻璃抗刮性、耐久性、耐環境性都很強，不過不會產生電容變化的絕緣物觸控面板無法運作，因此手套觸控無法操作
- 表面電容方式(Surface Capacitive)與投射電容方式相同，都是感測靜電容量的變化，若將投射電容方式視為四線阻抗膜方式，表面電容方式就等於五線阻抗膜方式，其中第五線就是人體
- 表面電容方式的結構如圖8所示，是由透明導電膜與四角落的電極構成，操作時對四角落的電極施加相同電壓，面板整體會形成均勻電界，全部都是同相位時，面板上的電容會放電，此時電流不會流動
- 當手指觸控面板時，變成與利用電容器接地的狀態相同，電流從四角落通過手指流動，越靠近觸控部位的電極電流值越大，此時只要量測來自四角落的電流量的比率，就可以判斷特定部位
- 複數接點並列形成滑塊(Slider)，可以感測手指的移動位置
- 由於電容式觸控感測器操作時完全沒有觸壓感，因此某些設計刻意組合機械結構，製成具備機械感測機構的觸控感測器，操作時可以獲得傳統機械接點式的操作感受
- 圖10(d)呈現的鋸齒狀為滑塊用，它可以感測手指處於水平方向的方位，應用在類似MP3等歌曲點播、音量調整，要求以手指橫向操作的產品上
- 弛張振盪方式利用電阻器與定電流電源使電容器充電，接著量測一定電壓的時間，當手指觸壓面板時，電容器的容量越大，站立時間則越來越遲緩

觸控式螢幕的玄機

觸控螢幕的應用非常廣泛，例如遊客導覽系統、自動櫃員機、銷售點終端機、工業控制系統等。在2000年，六家專門廠商加上幾家大公司的觸控產品部門，總產值高達八億美元。由於這種介面使用方便、經久耐用，而且花費不高，因此市場還在成長之中

blog.sina.com.tw/...article.php - Preview

touch sensor screen

電阻式螢幕，用手指或其他觸頭輕按就會產生電壓；電容式螢幕，手指會吸取微小的電流（常用於筆記型電腦的觸控板）。至於第三種波動式螢幕，則是用聲波或紅外線覆蓋整個表面，而手指或觸頭會阻斷這些駐波圖樣
電阻式螢幕是歷史最久、用途最廣，也是價格最低的一種，而且任何觸頭（無論手指或筆尖）都可以使用。電容式螢幕必須使用手指，或是接有地線的觸頭，以便傳導電流。波動式螢幕則是最新且最昂貴的類型。表面聲波螢幕必須用手指或軟式觸頭（例如鉛筆上的橡皮擦）輕觸，以吸收表面能量；紅外線觸控螢幕則可使用任何觸頭
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- 用指甲（而不是皮膚）輕壓螢幕，假如螢幕有反應，就可能是電阻式或紅外線式螢幕。果真如此，再同時用兩根手指分別輕壓螢幕上兩點。假如游標移到其中一根手指下方，這裝置使用的就是紅外線（軟體只記錄第一個接觸點）；假如游標移到兩根手指之間，螢幕就是電阻式（兩個接觸點皆有影響力）。假如這個裝置對指甲毫無反應，你的下一步還是用兩根手指分別輕壓螢幕上兩點。這時候，如果游標移到其中一根手指下方，那麼這螢幕使用的原理是聲波；假如游標移到兩根手指中間，它就是電容式觸控螢幕

電容式欲勝電阻式多點觸摸還需要更多殺手應用

由於電容觸摸屏可以實現多點觸摸，並在亮度和耐用性上超過電阻觸摸屏，有不少人認為未來它將逐漸取代後者。但問題的關鍵是，何時它的價位才能與電阻式競爭？多點觸摸有哪些殺手應用？電容觸摸屏控制IC是不是也會走集成之路？它是與前端顯示模組集成還是後端主晶片集成？

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touch sensor screen

由於先天結構(原理)上的原因，使用一段時間後需要重新對觸摸屏進行校正
電阻式方案已經非常成熟，一般都是和液晶屏打包配套，成本比較低
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- 電阻式觸摸技術也能做出與蘋果iPhone手機的多點觸摸類似功能，即支援手指滑動指令，支援手觸翻轉介面
- 電容性觸摸屏目前還不能很好地支持快速手寫輸入
- 在電容觸摸屏端已可識別手寫輸入的定位與軌跡，現在正在研發的是後端處理晶片如何來識別這些資訊，並傳達出來
- 多點觸摸分兩種：識別多點方向(Multi-Touch Gesture)和判斷多點位置(Multi-Touch All-Point)
- 在電容式技術的應用上，你可以看見觸控式面板和IC控制器會被安排放得非常接近，因為這個技術需要探測電流容量非常微弱的轉變，同時越長的電線引起信號干擾耦合影響的機會越大，造成錯誤觸控

25 Aug 08

Knowing how sensors work on the GoGo board

www.gogoboard.org/...makingSensors.xsp - Preview

GoGo sensor DIY

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- You can simply connect two wires or paper clips to pins 1 and 2 of the GoGo board to measure humidity in the soil.
- This same idea can be used to make a water detector sensor. When the two wires touch water, the sensor readings will change.
- You can improve the humidity sensor by connecting the two wires to a piece of gypsum, plaster, or any other material that absorbs water

29 Mar 08

COLOR SENSORS TUTORIAL

www.societyofrobots.com/sensors_color.shtml - Preview

5star DIY calibration color light photoresistor project sensor similarity trick tutorial

Suppose you have a sensor that can see many different colors, such as a
photoresistor. How would you use this sensor to detect
red apples vs. green apples?
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- If you shine a red light (such as from a red LED) on both apples, the red apple will reflect much more light than the green apple.
  As such, the apple that appears the brightest to your sensor will be the red apple.
- photoresistors have different levels of sensitivity to different colors.
  Typically photoresistors are optimal and peak at around 520nm. They are also sensitive to distance away from the target.
- The ambient light (for example, sunlight coming in through your window) can change
  throughout the day. You will need to shield your sensors from this light.
- different color LED's shine at different wavelengths and different brightnesses,
- In reality you must calibrate your sensors before they will work.
- equation:
  
  abs(new_reading - calibrating_reading)/calibrated_reading * 100 = similarity
  
  now using our numbers:
  
  grey floor = (108 - 95)/95 * 100 = 13.7% different
  
  white line = (108 - 112)/112 * 100= 3.6% different
  
  compare: white line < grey floor
  
  therefore the sensor sees a white line
- To detect two colors, of an infinite number of shades, you just need one LED and one sensor.
- if you wanted three different colors it would look something like this:
- Programming your color sensor is very easy. You simply turn on a LED with a digital output pin,
  wait about 50ms for the photoresistor to change (photoresistors are much much slower than
  infrared sensors), take a reading with an analog pin,
  then turn off the LED (if you have more than one LED).
- your color range sensor won't have a range of more than a few inches at most, depending on the brightness
  of your LED.
- So what if we had the LED shine for only 50ms?
  Well, that's 1 / .05 = 20, or 1/20th of a second. This means that if you shine your LED for only 50ms, then it can
  take about 10 to 20 times more current, and therefore shine about 10 to 20 times brighter.

10 Feb 08

WiiLi.org Wii Linux - Wiimote

www.wiili.org/Wiimote - Preview

IR UI Wii Wiimote accelerometer motion sensor

The motion of the remote is sensed by a 3-axis linear accelerometer located slightly left of the large A button.
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- The Wiimote does not normally report motion sensor readings to the host, but can be requested by sending SET_REPORT request to channel 0x12:
  
  (52) 12 00 31
  
  The 3rd byte is a bitmask. 0x01 turns on the rumble, and 0x04 turns on continuous output. If 0x04 is not set, packets are only output when the values change (almost always when the motion sensor is enabled). If 0x04 is set, values are output continuously. In continuous mode, the device will send data at 100 packages per second.
- Nintendo discovered the motion sensors were not accurate enough to use the remote to control an on-screen cursor. To correct this, they augmented the remote with an infrared image sensor on the front designed to locate two IR beacons within the controller's field of view. The beacons are housed within a device misleadingly called the Sensor Bar.

Electric Field Imagaing

web.media.mit.edu/efs.html - Preview

UI electric electrostatics field fish motion sensor

Electric Field Sensing lets machines inexpensively sense
in 3 dimensions, with high precision and fast update rates.
The thesis explains how to extract the available geometrical
information from any sized electric field sensing array. A single
channel provides a touch sensitive button; a few channels enable a 3d
mouse, and many channels enable a kind of imaging.
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Wiimote Hack - Hack a Wii - Wiimote Hacks, Mod Chips, DIY Nintendo Wii projects and more

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DIY Wii Wiimote hack sensor

09 Feb 08

Flashing LED - BEAM Wiki

www.beam-wiki.org/...index.php - Preview

BEAM LED electronics light sensor

A flashing LED is just an LED with a built-in microcircuit to cause it to flash periodically.
Like other LEDs, FLEDs are light-sensitive, and so flash faster in brighter light.

Electronics Applications

www.asc.vic.edu.au/...cations%20of%20electronics.htm - Preview

4star LDR LED diode electronics photodiode sensor termistor

When
light shines on the LDR, it has low resistance and allows current to flow. When light does not shine on it, the LDR has
a very high resistance, and a much smaller current will not flow through it.
The
current through a photodiode is directly proportional to the light
intensity
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- The photodiode and phototransistor can be both photovoltaic (generators
  of potential difference) and photoconductive (modifiers of an electric
  current), depending on the application.
- A
  reverse-biased photodiode operates in what is called photoconductive mode,
  since the conduction of the semiconductor junction varies with the illuminating
  light intensity. If the reverse-biased
  voltage is relatively large (i.e. several volts) the reverse-biased photodiode
  will have a very fast response time (much faster than an LDR) and is suitable
  for detecting light signals that vary down to a time scale of a fraction of a
  microsecond.

21 Jan 08

LED Touch sensor

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LED photoconductor reverse-biased sensor touch

Bi-Directional LEDs

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LED capacitor embedded light photovoltaic reverse-biased sensor

an LED by itself will generate a tiny DC voltage when exposed to a light source of the same or higher frequency of the LED. I think of this as photovoltaic operation. Any high-impedance voltmeter can measure this voltage, and it ranges based on intensity from 0 to 1.5 volts
using the LED as a light dependent capacitor. By reverse biasing the LED, a charge is placed on the junction. This charge is then dissipated by the LED’s photovoltaic properties once the reverse bias is removed.
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- Step 1> Forward bias the led array (all LEDs lit)
- Step 2> Reverse bias the first led in the array.
- Step 3> Switch the cathode connected pin into a high-z input mode and connect it to the microcontrollers ADC.
- Step 4> Perform an analog to digital conversion on the LED, reading the voltage potential stored in the LED. I’ve obtained values around 3.3 volts while the led is “dark” and as low as 0.9 volts while the led is brightly lit by the rest of the array via a mirror.
- Step 5> Forward bias the LED again
- The problem with a faster sample time is I loose dynamic range or “brightness sensitivity”. I believe this is due to the fact the LED does not discharge fast enough.
- A forum member on the linear1 forum recommended I place a resistor across the LED to speed up this discharge

LED array turned into touch button

www.trnmag.com/...touch_button_Brief_122904.html - Preview

LED UI sensor touch

The researcher's prototype acts as a touch button. Because it
is also a display, it is also capable of showing prompts.
The researcher's technique requires at least two light-emitting
diodes, one that senses light and one that emits light. When a translucent
or reflective object like a finger makes contact, it reflects light from
the emitting diode onto the sensing diode

Matrices as Sensors

projects.dimension-x.net/...63 - Preview

4star LED embedded light sensor

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York Jong's Library tagged sensor → View Popular

资料收集：常用传感器 (www.ourdev.cn)

偶得一触摸按键电路，请大虾分析其原理（附图） (www.ouravr.com)

ADC without ADC

Bayer filter - Wikipedia, the free encyclopedia

ATMEL 业界最强电容触摸技术 Atmel Touch Library

Atmel Products - Touch Technology - Touch Library

電容式觸控技術百家爭鳴

觸控式螢幕的玄機

電容式欲勝電阻式多點觸摸還需要更多殺手應用

Knowing how sensors work on the GoGo board

COLOR SENSORS TUTORIAL

WiiLi.org Wii Linux - Wiimote

Electric Field Imagaing

Wiimote Hack - Hack a Wii - Wiimote Hacks, Mod Chips, DIY Nintendo Wii projects and more

Flashing LED - BEAM Wiki

Electronics Applications

LED Touch sensor

Bi-Directional LEDs

LED array turned into touch button

Matrices as Sensors

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