A projection screen limit method and limit mechanism

Abstract

The invention discloses a projection curtain limiting method and limiting mechanism. The limiting mechanism comprises a power supply, a controller and a control circuit, and a driving motor is mounted in a winder shell of a projection screen; the driving motor is connected with a cloth shaft; during the forward and reverse rotation of the driving motor, the cloth shaft can roll and unroll the curtain; two ends of the control circuit are respectively connected with the power supply and an AC synchronous motor; the control circuit comprises a zero-crossing detection circuit, a single-chip microcomputer, a forward silicon controlled rectifier and a reverse silicon controlled rectifier. The zero-crossing detection circuit detects the pulse number of an alternating current when the driving motor rotates, the single-chip microcomputer stores an upper boundary point, a lower boundary point and the pulse number and sends signals to the forward silicon controlled rectifier and the reverse silicon controlled rectifier, and the forward silicon controlled rectifier and the reverse silicon controlled rectifier control the alternating current synchronous motor to rotate forwards, turn over and stop. The zero-crossing detection circuit is adopted to measure the pulse of the alternating current for metering, and the silicon controlled rectifier is adopted, so that the accuracy is higher.

Description

technical field [0001] The invention belongs to the field of projection screen equipment, and in particular relates to a projection screen limiting method and a limiting mechanism. Background technique [0002] Projection screens, combined with projectors, are used in movies, offices, home theaters, large conferences and other occasions. They are tools for displaying images and video files, and they are divided into many specifications and sizes. In order to save office space and keep clean when the projection screen is not in use, the projection screen is rolled up. In order to ensure that the projection screen stops rotating when the projection screen rises and falls to the limit position, electric screen travel limit controllers are often used in the industry. The electric screen stroke limit controller is used to control the projection screen to rise or fall to the right position, and the screen motor will stop working when the power is cut off, and it is also a limiter...

AI Technical Summary

Problems solved by technology

[0017] Aiming at the above-mentioned deficiencies in the prior art, the technical problem to be solved by the present invention is that the existing electric curtain travel limit controller is used as a mechanical control method, which has high cost, high failure rate, and cumbersome debugging; when the relay exists, the company adopts Delay is not conducive to precise control, and the number of turns and the two-stage control method before and after are more complicated

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