Adafruit
Reflective IR Sensor with 470 and 10K Resistors
This Reflective IR Sensor is a simple plastic casing with two elements - an IR LED and an IR phototransistor. You can control the IR LED and turn it on to bo...
This Reflective IR Sensor is a simple plastic casing with two elements - an IR LED and an IR phototransistor. You can control the IR LED and turn it on to bounce IR off objects to determine their reflectivity. White & light colored stuff will bounce the light, so you can detect it. Black & dark colored stuff will absorb the IR light so that it isn't detected. Likewise, if something isn't in the way of the sensor, it won't trigger either.
These sensors are handy when you want to detect if something has passed by the sensor, or a very simple hand-detector. Also sometimes these are used as rotary encoder, if the encoder wheel has black and white stripes, the photo sensor is fast enough to tell you the RPM.
Comes with a 470 ohm resistor (for biasing the IR LED) and a 10K resistor which you can use as a pull-up resistor for the phototransistor. The sensor is breadboard friendly and easy to solder to.
This works best when detecting a light-colored object approximately 5mm away - 2mm to 10mm worked fairly well but your results may vary with the LED brightness, object shininess, etc.
Jargon buster
Plain-language definitions for the technical terms used above.
- encoder
- A device attached to a motor or shaft that reports movement, such as rotation steps or position. In a pump system, an encoder can help measure or control how much the motor has turned, which affects how repeatable the watering amount can be.
- LED
- A light-emitting diode is a small electronic component that lights up when current flows through it in the correct direction. In this kit, LEDs create the flashing effect, so polarity and correct soldering matter for the project to work.
- phototransistor
- A light-sensitive transistor that changes its electrical output when light hits it. Compared with a modulated IR receiver, a simple phototransistor can be more affected by ambient light, so it may need extra filtering or careful setup.
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