Traditional Chinese Practical Blind Hearing: Circuit Design, Parts List & Workshop Prototype Guide
In short: Traditional Chinese Practical Blind Hearing. This entry documents a circuit & prototype taken from Chinese practical-technology literature, written for small-scale makers and home producers. The text below is the full English translation of the original Chinese workshop notes, covering materials and quantities, the step-by-step sequence, and the practical cautions recorded in the source. Roughly 2508 words of English technical text, translated and preserved without editing. It is intended for experimental and reference use, not for regulated or commercial certification.
Blind people listen and touch voltmeterThe circuit shown in Figure 121 can convert a DC input voltage in the range of 0 to 100mV into a sound signal. When the measured voltage exceeds the reference voltage, the earphones will emit sound.Transistors VD1 and VD2 form a reference voltage source, providing a reference voltage for operational amplifier A1, and A1 forms a voltage comparator. Operational amplifier A2 forms a self-excited multivibrator to provide audio signals to the headphones. Select F007 for A1 and A2.Figure 121Potentiometer RP1 is a reference voltage potentiometer, potentiometer RP2 is a decimal switch, and potentiometer RP3 is a zero-adjustment potentiometer. When the measured voltage exceeds the reference voltage from the earphones, a blind person can touch the Braille on the decimal switch to read the input voltage. …
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