{"product_id":"qtr-1a-reflectance-sensor-2-pack","title":"QTR-1A Reflectance Sensor (2-Pack)","description":"\u003cp\u003eThe QTR-1A reflectance sensor carries a single infrared LED and phototransistor pair in an inexpensive, tiny 0.5\" x 0.3\" module that can be mounted almost anywhere and is great for edge detection and line following. \u003cstrong\u003eThe reflectance measurement is output as an analog voltage.\u003c\/strong\u003e\u003c\/p\u003e\n\u003cp\u003eThis sensor is sold in packs of \u003cstrong\u003etwo\u003c\/strong\u003e units.\u003c\/p\u003e\n\u003cp\u003e\u003cstrong\u003eNote:\u003c\/strong\u003e The QTR-1A reflectance sensor requires an analog input to take readings. The similar \u003ca href=\"\/en-eu\/products\/qtr-1rc-reflectance-sensor-2-pack\" target=\"_blank\"\u003eQTR-1RC reflectance sensor\u003c\/a\u003e is available with a digital I\/O-compatible output.\u003c\/p\u003e\n\u003cp\u003eThe Pololu QTR-1A reflectance sensor carries a single infrared LED and phototransistor pair. The 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.\u003c\/p\u003e\n\u003cp\u003eThe LED current-limiting resistor is set to deliver approximately 17 mA to the LED when VIN is 5 V. The current requirement can be met by some microcontroller I\/O lines, allowing the sensor to be powered up and down through an I\/O line to conserve power.\u003c\/p\u003e\n\u003cp\u003eThis sensor was designed to be used with the board parallel to the surface being sensed. Because of its small size, multiple units can easily be arranged to fit various applications such as line sensing and proximity\/edge detection.\u003c\/p\u003e\n\u003cp\u003e\u003cstrong\u003eSpecifications\u003c\/strong\u003e\u003c\/p\u003e\n\u003cul\u003e\n\u003cli\u003eDimensions: 0.3\" x 0.5\" x 0.1\" (without optional header pins installed)\u003c\/li\u003e\n\u003cli\u003eOperating voltage: 5.0 V\u003c\/li\u003e\n\u003cli\u003eSupply current: 17 mA\u003c\/li\u003e\n\u003cli\u003eOutput format: analog voltage\u003c\/li\u003e\n\u003cli\u003eOutput voltage range: 0  to supplied voltage\u003c\/li\u003e\n\u003cli\u003eOptimal sensing distance: 0.125\" (3 mm)\u003c\/li\u003e\n\u003cli\u003eMaximum recommended sensing distance: 0.25\" (6 mm)\u003c\/li\u003e\n\u003cli\u003eWeight without header pins: 0.008 oz (0.2 g)\u003c\/li\u003e\n\u003c\/ul\u003e\n\u003cp\u003e\u003cstrong\u003eInterfacing with the QTR-1A Output\u003c\/strong\u003e\u003c\/p\u003e\n\u003cp\u003eThere are several ways you can interface with the QTR-1A output:\u003c\/p\u003e\n\u003cul\u003e\n\u003cli\u003eUse a microcontroller’s analog-to-digital converter (ADC) to measure the voltage.\u003c\/li\u003e\n\u003cli\u003eUse a comparator with an adjustable threshold to convert the analog voltage into a digital (i.e. black\/white) signal that can be read by the digital I\/O line of a microcontroller.\u003c\/li\u003e\n\u003cli\u003eConnect the output directly to the digital I\/O line of a microcontroller and rely upon its internal comparator.\u003c\/li\u003e\n\u003c\/ul\u003e\n\u003cp\u003eThis 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\u003c\/p\u003e\n\u003cp style=\"text-align: left;\"\u003e\u003cimg alt=\"\" src=\"\/\/cdn.shopify.com\/s\/files\/1\/0174\/1800\/files\/0J638.1200_medium.png?v=1476282898\" style=\"float: none;\"\u003e\u003cimg src=\"\/\/cdn.shopify.com\/s\/files\/1\/0174\/1800\/files\/0J640.1200_medium.png?v=1476282952\" alt=\"\"\u003e\u003c\/p\u003e\n\u003cp\u003eFor more resources check out the \u003ca href=\"https:\/\/www.pololu.com\/docs\/0J20\"\u003ePololu AVR library\u003c\/a\u003e and \u003ca href=\"https:\/\/www.pololu.com\/docs\/0J19\"\u003eArduino library\u003c\/a\u003e for these sensors.\u003c\/p\u003e\n\u003cp\u003e\u003cstrong\u003eIncluded Components\u003c\/strong\u003e\u003c\/p\u003e\n\u003cp\u003eThis module has a single mounting hole intended for a #2 screw (not included); if this mounting hole is not needed, this portion of the PCB can be ground off to make the unit even smaller. Each pack of two reflectance sensors includes sets of straight male header strips and right-angle male header strips, which allow you to mount them in the orientation of your choice (note: the header pins might ship as 1×6 strips that you can break into two 1×3 pieces). You can also solder wires, such as ribbon cable, directly to the pads for the most compact installation.\u003c\/p\u003e","brand":"Pololu","offers":[{"title":"Default Title","offer_id":32140869258,"sku":"POL-2458","price":4.95,"currency_code":"EUR","in_stock":false}],"thumbnail_url":"\/\/cdn.shopify.com\/s\/files\/1\/0174\/1800\/products\/0J4714.1200.jpg?v=1476283100","url":"https:\/\/shop.pimoroni.com\/en-eu\/products\/qtr-1a-reflectance-sensor-2-pack","provider":"Pimoroni Ltd","version":"1.0","type":"link"}