Photoelectric sensor and the application of various principles of photoelectric switches
Time:2013-03-21
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Just a form of electromagnetic radiation, radio waves and their characteristics as X-ray, transmission speed is about 300,000 km / s, so it can launch an instant by his reception. Infrared switch photoelectric switch is to use the human eye is not visible (wavelength of 780nm-1mm) of the near-infrared and infrared to detect, distinguish objects. Photovoltaic devices by the weak beam can be instantly launched a secure and accurate transmission and reception.
Important function of photoelectric switch is able to handle the intensity of light changes: use of optical components, beam in the media center to change; the use of reflective light beam to an object; so long after the moment the beam to return after launch. Photoelectric switch is a transmitter, receiver and detection circuit composed of three parts. Transmitter at the target launch beam, the beam emission from light-emitting diode generally (LED) and laser diodes.
Beam continuously firing, or to change the pulse width. By pulse modulation of the beam radiation intensity after the launch of multiple choice, and indirectly toward the goal is not to run. Receivers are composed of photodiodes or phototransistors. In front of the receiver, equipped with optical components such as lenses and aperture. In the back of the detection circuit, it can filter out the valid signal and application of the signal.
Photoelectric switches can be divided on the radio type, diffuse reflective, specular reflective.
Photoelectric switch on the radio: transmitter and receiver by the composition, structure is both separated from each other, in the case of the beam is interrupted will produce a switch signal changes, the typical way is located on the same axis photoelectric switch each other separation of up to 50 meters. Features: identify opaque reflective objects; effective span, because the beam across the sensing distance of only one; less susceptible to interference, the right to use reliably in the field or in dusty environments; device high consumption, two elements must be the laying of cables.
Diffuse reflection type photoelectric switch: when the switch launch beam, the objectives of diffuse reflection, the transmitter and receiver consisting of a single standard components, when combined with enough light to return the receiver, the switch state changes, the role range of typical values up to 3 meters. Features: Effective range is decided by the target reflectivity, target surface properties and by the decisions and color; smaller assembly cost, when the switch is formed by a single element, usually rough positioning can be achieved; with background suppression adjustment measure distances ; on the target on the dust-sensitive and reflection on the changing performance targets sensitive.
Specular reflection type photoelectric switch: the transmitter and the receiver is composed of a standard configuration, the light beam emitted from the emission side of the mirror is reflected, or back to the receiver, when the beam is interrupted to generate a switch signal when changes. Light signal by the time twice the duration of effective distance from 0.1 to 20 meters. Features: identifying opaque objects; with mirror components, forming a high effective distance range; less susceptible to interference, the right to use reliably in the field or in dusty environments.
