A program-controlled frequency distance adjustment method for reflective infrared photoelectric sensors

Abstract

The invention relates to a reflection-type infrared photoelectric sensor and a program control frequency distance adjustment method thereof. The sensor comprises an infrared emission circuit, an infrared receiving circuit, a one-chip microcomputer, an output interface circuit and a setting circuit. The infrared emission circuit is driven by the one-chip microcomputer and can emit infrared pulse light with a modulation frequency of f. The infrared receiving circuit comprises an infrared remote control reception module with a central receiving frequency of f0. The setting circuit sends a setting request signal to the one-chip microcomputer. The one-chip microcomputer receives a distance adjustment request signal and controls the infrared pulse optical frequency to adjust an effective detection range of the sensor. The photoelectric sensor and the distance adjustment method achieve program control frequency distance adjustment and take full advantage of software resource. The circuit structure is simplified, and intelligentized setting is achieved. All setting can be finished by utilization of only one button, which is convenient and practical. In addition, output modes of an output interface can be switched, usage is flexible and convenient, and the application range of the sensor is widened.

Description

technical field [0001] The invention belongs to the technical field of photoelectric sensors, in particular to a program-controlled frequency distance adjustment method for reflective infrared photoelectric sensors. Background technique [0002] The working principle of the reflective infrared photoelectric sensor is: emit infrared light with a certain modulation frequency through the infrared emitting tube, and the reflected light is detected by the photosensitive tube and amplified and demodulated to determine whether the detected object enters the effective detection range, and then output the switch signal , the purpose of using modulated light is to improve the ability of anti-interference. Generally, the modulation frequency of the transmitted light is equal to the central reception frequency of the receiving circuit. [0003] Common reflective infrared photoelectric sensors are divided into two types, namely, fixed detection distance type and adjustable detection dis...

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Problems solved by technology

However, this method also has defects: First, increasing the amplification gain can improve the sensitivity, but it reduces the anti-interference ability; second, the adjustable resistor has mechanical contact, which is easily affected by the environment and changes its inherent parameters, which in turn affects the sensor’s performance. stability

[0007] It is known that a class of phase detection and detection circuits represented by phase-locked loops all have frequency-selective characteristics. When the frequency of the input signal is close to its center receiving frequency, it has the greatest sensitivity. When it is large, the sensitivity drops to zero, that is to say, as the frequency shifts, the sensitivity will gradually drop, which provides the possibility to adjust the sensitivity of the sensor by frequency conversion

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