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QTR-1A Reflectance Sensor (2-Pack)

SKU: POLOLU-2458 Brand: Pololu
The 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. The reflectance measurement is output as an analog voltage. This sensor is sold in packs of two units.
$8.40 AUD, inc GST
$7.64 AUD, exc GST

In stock, ships same business day if ordered before 2PM
Delivered by Fri, 12th of Aug

Quantity Discounts:

  • 10-25 $7.33 (exc GST)
  • 25+ $7.10 (exc GST)
- +

3 from local stock, 1 supplier stock; your order will dispatch between Dec 1 to Dec 10. And yes, stock levels and lead times are accurate!

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  • $10+ Express (2+ days*, tracked)
  • FREE Pickup (Newcastle only)

Shipping costs may increase for heavy products or large orders.

Exact shipping can be calculated on the view cart page.

*Conditions apply, see shipping tab below.

Note: The QTR-1A reflectance sensor requires an analog input to take readings. The similar QTR-1RC reflectance sensor is available with a digital I/O-compatible output.

Functional Description

The 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.

The 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.

This 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.

For a line sensor with eight of these units arranged in a row, please see the QTR-8A reflectance sensor array; for a similar array of three slightly different sensor components, see the QTR-3A. For a smaller sensor with longer range, and intended for use with the board perpendicular to the surface, please see the QTR-L-1A reflectance sensor.

QTR sensor size comparison. Top row: QTRX-HD-07, QTR-HD-07; middle row: QTR-3, QTR-1, QTR-L-1; bottom row: QTR-8.

Specifications

  • Dimensions: 0.3" x 0.5" x 0.1" (without optional header pins installed)
  • Operating voltage: 5.0 V
  • Supply current: 17 mA
  • Output format: analog voltage
  • Output voltage range: 0  to supplied voltage
  • Optimal sensing distance: 0.125" (3 mm)
  • Maximum recommended sensing distance: 0.25" (6 mm)
  • Weight without header pins: 0.008 oz (0.2 g)

Interfacing with the QTR-1A Output

There are several ways you can interface with the QTR-1A output:

  • Use a microcontroller’s analog-to-digital converter (ADC) to measure the voltage.
  • Use 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.
  • Connect the output directly to the 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-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.

Pololu's Pololu AVR library provides functions that make it easy to use these sensors with Pololu's Orangutan robot controllers; please see the QTR Reflectance Sensors section of Pololu's library command reference for more information. Pololu also have a Arduino library for these sensors.

Included Components

This 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.

People often buy this product together with:

TB6612FNG Dual Motor Driver Carrier TB6612FNG Dual Motor Driver Carrier
QTR-8A Reflectance Sensor Array QTR-8A Reflectance Sensor Array
QTR-L-1A Reflectance Sensor (2-Pack) QTR-L-1A Reflectance Sensor (2-Pack)

Dimensions

Size: 0.3" × 0.5" × 0.1"1
Weight: 0.2 g2

Identifying markings

PCB dev codes: irs01a

Notes:

1
Without optional included header pins.
2
For a single sensor without included optional header pins.

Documentation and other information

File downloads

Recommended links

This product is listed in:

Sensors>Reflectance

Product Comments

Exact shipping can be calculated on the view cart page (no login required).

Products that weigh more than 0.5 KG may cost more than what's shown (for example, test equipment, machines, >500mL liquids, etc).

We deliver Australia-wide with these options (depends on the final destination - you can get a quote on the view cart page):

  • $3+ for Stamped Mail (typically 10+ business days, not tracked, only available on selected small items)
  • $6+ for Standard Post (typically 6+ business days, tracked)
  • $10+ for Express Post (typically 2+ business days, tracked)
  • Pickup - Free! Only available to customers who live in the Newcastle region (only after we email you to notify your order is ready)

Non-metro addresses in WA, NT, SA & TAS can take 2+ days in addition to the above information.

Some batteries (such as LiPo) can't be shipped by Air. During checkout, Express Post and International Methods will not be an option if you have that type of battery in your shopping cart.

International Orders - the following rates are for New Zealand and will vary for other countries:

  • $11+ for Pack and Track (3+ days, tracked)
  • $16+ for Express International (2-5 days, tracked)

If you order lots of gear, the postage amount will increase based on the weight of your order.

Our physical address (here's a PDF which includes other key business details):

Unit 18, 132 Garden Grove Parade
Adamstown
NSW, 2289
Australia

Take a look at our customer service page if you have other questions such as "do we do purchase orders" (yes!) or "are prices GST inclusive" (yes they are!). We're here to help - get in touch with us to talk shop.

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