Traditional Chinese Practical Eye protection (1): Circuit Design, Parts List & Workshop Prototype Guide

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Vision Protector(1)Reading for a long time under too strong or too weak light will damage your vision. The vision protector introduced in this article will sound an alarm and light up when the light is too strong or too weak, and the green light will turn on when the light is normal. When reading for too long, the protector red light and piezoelectric ceramic will remind you that it's time to take a break.Circuit working principle:The vision protector consists of five parts: photoelectric conversion circuit, comparison circuit, display circuit, alarm circuit, and timing circuit. Figure 158-1 is its block diagram, and Figure 158-2 is its circuit diagram.Figure 158-1(1) Photoelectric conversion circuitIt consists of two voltage dividers, a photoresistor and a variable resistor. RG1 and RP1 form voltage divider 1 and are used for strong light monitoring. RG2 and RP2 form voltage divider 2 and are used for low light monitoring. When the light is too strong, the RG1 value becomes small, and the voltage divider 1 outputs a high level; when the light is too strong, the RG1 value becomes small, and the voltage divider 1 outputs a high level; when the light is too weak, the RG2 value becomes large, and the voltage divider 2 outputs a low level. When the light is normal, voltage divider 1 outputs low level and voltage divider 2 outputs high level.(2) Comparison and display circuitThe comparison and display circuit is composed of XOR gates IC1-1, IC1-2, IC1-3, R4, R5, R6, VD1, VD2, and VD3. VD1~VD3 are light-emitting diodes. IC1-1, R6, and VD3 are strong light displays, IC1-2, R5, and VD2 are low-light displays, and IC1-3, R4, and VD1 are normal displays.(3)Alarm circuitThe alarm circuit consists of an oscillator and a controller. IC1-4, IC3-4, and IC2-1 form the controller, and IC2-4 form the oscillator. When one input terminal of IC2-1 is low level, the controller outputs a high level at the output terminal of IC1-4 to make the oscillator work and send out an alarm signal. If there is a high level signal input at the input end of IC3-4, the oscillator also works.(4) Timing circuitThe timing circuit is composed of IC3-1, IC3-2, IC3-3, R1, R2, and C1. IC3-1, IC3-2, R2, and C1 form a monostable timing circuit, and the timing time is determined by R2 and C1. …

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