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Optical Sensors - Photointerrupters - Slot Type - Transistor Output

QVA21214 Application Field and Working Principle

The QVA21214 is a slot-type photointerrupter optical sensor. It uses an infrared emitting diode (IRED) and a silicon photo-transistor housed in a leadless plastic package. This type of optical sensor allows non-contact detection of objects without mechanical contact. It is applied in a vast number of fields, and is especially effective for high-speed detection of items such as pieces being removed from a manufacturing line, parts passing through a detection point, defective product detection, and general area protection and detection. The QVA21214 is also used in areas such as those with high-speed equipment, dust-prone areas, areas with debris, or those with magnetic or electric pressures.

In terms of its working principle, the QVA21214 operates by transmitting an infrared light beam between the IRED and the photo-transistor. In a normal condition, the light beam is uninterrupted, allowing for the transistor to maintain a closed contact between the collector and the emitter. This, in turn, results in a high output voltage at the transistor output terminal. When the light beam is blocked or interrupted, a voltage drop occurs at the transistor output terminal. As a result, a detection signal is then transmitted. In addition, the QVA21214 also utilizes a built-in resistor, which allows for the voltage supplied to the IRED to be regulated. This resistor sets a maximum current to be blessed through the IRED, thus preventing it from being overloaded.

The resins used in the QVA21214 are particularly resistant to temperature, humidity, dust, and various acidic and alkaline substances. This type of optical sensor also offers a long lifetime of up to 50 million operatings due to the use of an interference prevention mechanism. In addition, the leadless package ensures it can be used in thin and small applications. These features have made the QVA21214 a popular choice in various application fields, especially in those requiring a reliable, high-speed detection capability.

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