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CNY70 reflective sensor is an infrared sersor allowing alteration of an analog electrical signal depending on the amount of infrared light that is reflected by an object near the sensor, in this way the sensor can be used as a switch or as a reader analog signal.
There are two types of application, a proximity sensor and a tachometer. The proximity sensor is located perpendicular to a reflective surface which means that, at steady state there is always a high amount of energy reflected back to the sensor, when an object with different surface finish is interposed between the reference surface and the receptor alters the amount of reflected light which changes the signal and thus logical conditions are true that activates the green LED.
The tachometer has the same type of sensor but in this case is aligned perpendicular to a motorized wheel divided into two sections by a black and white tape, which shows two types of finishes differently reflecting infrared light from the sensor, the change in reflection generated by the rotation of the wheel causes it to generate a repetitive pulse received by the plate arduino, frequency between each change of signal is directly proportional to the angular velocity of rotation of the wheel, allowing computing the signal to reach a certain speed and activate the green LED.
The project is made with recycled materials so that was done at low cost and fast way.
Easy and Nice
The sensor data sheet: CNY70