H21A5

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H21A5 Application Field and Working Principle

The H21A5, belonging to the Optical Sensors - Photointerrupters - Slot Type - Transistor Output family, is anoptical sensing device used for measurement or counting purposes. It\'s meant for use in electronic control circuits, aswell as various industrial machinery.

Application of H21A5

The H21A5 is mainly used for the detection of objects passing through a detection slot. It is suitable for use inencoders, numerical counters, rotary cassettes and so on. It has various uses; measuring distance between objects,detecting the rotation direction of a motor shaft, detecting the amount of items as they pass through the slot, andpositioning of an actuator, among others.

Structure of H21A5

The H21A5 has an optical head in the form of an integrated optoelectronic component, consisting of an infrared emitter and a phototransistor arranged in a vertical line. This optical head is usually mounted by solder joint and fixed to a heat dissipator. The active window of the phototransistor is located in the middle between the infrared emitter and the collector. The collector of the phototransistor can be either a PNP type or an NPN type. The emitterof the phototransistor is connected to the ground. An opaque slotted shield with input openings is placed in front of the sensor, so that any object passing through its opening will interrupt the optical path and the transistor will be activated and produce an output signal.

Working Principle of H21A5

When the slot in the shield is not blocked by an object, the infrared beam emitted by the emitter passes through it and is received by the phototransistor. This will cause the phototransistor to be reverse biased and the collector current will be extremely low. When an object passes through the slot, the infrared beam will be blocked and the current output of the phototransistor will rise sharply, activating the transistor output and producing a signal.

This signal can be used to detect the number of objects passing through the slot, the speed of the objects, and the direction of rotation of a shaft, among other measurements. The H21A5 is widely used in automation, semiconductor, industrial control, and measurement systems, and can count moving objects up to a maximum speed of 2 kHz.

Conclusion

The H21A5 belongs to the Optical Sensors - Photointerrupters - Slot Type - Transistor Output family and is used for various measurement and counting purposes. Its structure consists of an integrated optoelectronic component made from an infrared emitter and phototransistor, along with an opaque slotted shield. Its working principle is based on the interruption of the infrared beam, which causes the phototransistor to be activated and produces an output signal. The H21A5 is a reliable and cost-effective solution for various sensor applications.

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