※本產品原廠代理從國外進口，有些交期較長，下訂前請詢問！
This sensor module has 8 IR LED/phototransistor pairs mounted on a 0.375" pitch, making it a great detector for a line-following robot. Pairs of LEDs are arranged in series to halve current consumption, and a MOSFET allows the LEDs to be turned off for additional sensing or power-savings options. Each sensor provides a separate analog voltage output.
這個感測器模組有八個成對的 IR LED/phototransistor 設置在 0.375” pitch ，提供循跡機器人ㄧ個很棒的偵測器。成對的 LED 串聯排列減半電流消耗，及 MOSFET 允許 LED 額外感測關閉或省電功能選擇。每ㄧ個感測器提供分開的類比電壓輸出。
QTR -8A 陣列循線感測器可延伸作為循線感測測器，但也可以當成一般用途近接獲反射感測器。對於八個成對的 IR 發射器及接收器 (phototransistor) 是一個便利的載板即使間隔只有 9.525mm 。每ㄧ個 phototransistor 連接到一個拉高 (pull-up) 電阻來形成一個電壓分離器，其產生 0V 及 VIN 間的 ( 標準 5V) 類比電壓輸出如同 IR 反射的功能。較低輸出電壓為較大反射的指標。
Note: The QTR-8A reflectance sensor array requires analog inputs to take readings. The similar QTR-8RC reflectance sensor array is available with digital I/O-compatible outputs, and the reflectance sensor is available individually as a QTR-1A reflectance sensor or QTR-1RC reflectance sensor.
Functional Description
The QTR-8A reflectance sensor array is intended as a line sensor, but it can be used as a general-purpose proximity or reflectance sensor. The module is a convenient carrier for eight IR emitter and receiver (phototransistor) pairs evenly spaced at intervals of 0.375" (9.525 mm). Each phototransistor is connected to a pull-up resistor to form a voltage divider that produces an analog voltage output between 0 V and VIN (which is typically 5 V) as a function of the reflected IR. Lower output voltage is an indication of greater reflection.
The outputs are all independent, but the LEDs are arranged in pairs to halve current consumption. The LEDs are controlled by a MOSFET with a gate normally pulled high, allowing the LEDs to be turned off by setting the MOSFET gate to a low voltage. Turning the LEDs off might be advantageous for limiting power consumption when the sensors are not in use or for varying the effective brightness of the LEDs through PWM control.
The LED current-limiting resistors for 5 V operation are arranged in two stages; this allows a simple bypass of one stage to enable operation at 3.3 V. The LED current is approximately 20-25 mA, making the total board consumption just under 100 mA. The schematic diagram of the module is shown below:
尺寸 : 2.95" x 0.5" x 0.125" ( 不含 header pins 安裝 )
- 操作電壓 : 3.3-5.0 V
- 供應電流 : 100 mA
- 輸出格式 : 8 analog voltages
- 輸出電壓範圍 : 0 V to supplied voltage
- 最適感測距離 : 3 mm
- 最大建議感測距離 : 6 mm
- 重量 ( 不含 header pins): 3.09 g
Specifications
- Dimensions: 2.95" x 0.5" x 0.125" (without header pins installed)
- Operating voltage: 3.3-5.0 V
- Supply current: 100 mA
- Output format: 8 analog voltages
- Output voltage range: 0 V to supplied voltage
- Optimal sensing distance: 0.125" (3 mm)
- Maximum recommended sensing distance: 0.25" (6 mm)
- Weight without header pins: 0.11 oz (3.09 g)
Interfacing with the QTR-8A Outputs
There are several ways you can interface with the QTR-8A outputs:
- Use a microcontroller’s analog-to-digital converter (ADC) to measure the voltages.
- Use a comparator with an adjustable threshold to convert each analog voltage into a digital (i.e. black/white) signal that can be read by the digital I/O line of a microcontroller.
- Connect each output directly to a digital I/O line of a microcontroller and rely upon its internal comparator.
This last method will work if you are able to get high reflectance from your white surface as depicted in the left image, but will probably fail if you have a lower-reflectance signal profile like the one on the right.
QTR -8A 輸出介面
使用微控制器類比到數位轉換器 (ADC) 來測量電壓
使用比較器 (comparator) 可調整閥值來轉換每ㄧ個類比電壓到數位 ( 如： black/white) 訊號，可以讀取微控制器數位 I/O line
直接地連接每ㄧ個輸出到微控制器的數位 I/O line 及以此來依靠內部比較器。
這最後的方法可以工作假如你可以從白色表面得到高反射 ( 左圖 ) 。但可能失敗假如你得到一個低反射訊號 ( 右圖 )
|  | | QTR-1A output 1/8" away from a spinning white disk with a black line on it. | | |  | | QTR-1A output 3/8" away from a spinning white disk with a black line on it. | |
模組可一分為二
假如你不需要或不適合所有八個感測器，你可以一分為二並能可以使用八個感測器在兩塊模組上 ( 如下圖 ) 。 PCB 可以兩側的穿孔做記號並彎折到斷裂分離。最後兩塊功能都是獨立的。
包含元件
這塊模組寄送時有 25-pin 0.1" header strip 及 100 Ohm through-hole 電阻 。可以將 header strip 弄成小塊及焊接到你的陣列感測器上。或是要安裝更緊密你可以直接焊到組件上。 Pins 在模組上的排列以便於使用 11X1 strip 或 8×2 strip 。 在陣列感測器一分為二時才需要使用電阻。
Our Pololu AVR library provides functions that make it easy to use these sensors with our Orangutan robot controllers; please see the QTR Reflectance Sensors section of our library command reference for more information. We also have a Arduino library for these sensors.
Breaking the Module in Two
If you don’t need or cannot fit all eight sensors, you can break off two sensors and still use all 8 sensors as two separate modules, as shown below. The PCB can be scored from both sides along the perforation and then bent until it snaps apart. Each of the two resulting pieces will function as an independent line sensor.
Included Components
This module ships with a 25-pin 0.1" header strip and a 100 Ohm through-hole resistor as shown below.
You can break the header strip into smaller pieces and solder them onto your reflectance sensor array as desired, or you can solder wires directly to the unit or use a right-angle header strip for a more compact installation. The pins on the module are arranged so that they can all be accessed using either an 11×1 strip or an 8×2 strip.
The resistor is required to make the two-sensor array functional after the original eight-sensor array is broken into two pieces. This resistor is only needed once the board has been broken.
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| Solder the included resistor to the 2-sensor array piece as shown to make the separated piece functional. |
