Traditional Chinese Practical High-sensitivity hearing aids (3): Circuit Design, Parts List & Workshop Prototype Guide

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High sensitivity hearing aid(3)The hearing aid composed of HDT6 integrated circuit and EC9-1 type hearing aid earphones has the following characteristics: (1) Due to the use of thick film integrated circuits and high-quality hearing aid earphones specially designed for deaf hearing aids, it has high sensitivity, good frequency response characteristics, clear sound quality, and noise reduction. Low sound and comfortable to wear; (2) Light weight, small size, easy to carry; (3) Stable and reliable performance, not afraid of collisions and falls, cheap price, very suitable for deaf patients to choose and use; (4) The peripheral circuit is simple, the components used are common, and easy to make and repair.Figure 106-1Circuit principle:The circuit schematic diagram is shown in Figure 106-1. When the external audio signal is sent to the resident pickup microphone BP, the audio signal is coupled by C1 and input to pin ① of HDT6. It undergoes three-level audio amplification inside the IC, and then performs power amplification. Finally, the amplified signal is output from pin ⑥, which directly drives the earphone to produce sound, and acts on hearing correction for deaf patients. In the figure, C1 and C2 are used for signal coupling; C3 and C4 are power supply decoupling capacitors to prevent howling; R2 is a feedback resistor, mainly used to improve sound quality and stabilize circuit operation; RP is a voltage divider, switch and volume adjustment potentiometer for people with hearing loss to adjust the sound level.Production and debugging:The printed circuit board drawn according to the circuit diagram is shown in Figure 106-2. The size of the printed board is not 1:1. Readers can determine the position of the pin arrangement holes based on the size of the HDT6IC, and then draw it by referring to Figure 106-2. Try to make it small and beautiful, and it is generally suitable to fit in a jacket pocket.The electret microphone BP should be a commercially available recorder microphone with higher sensitivity. During installation, weld hard wires with a thickness of 0.8 to 1.0mm on both poles of the microphone to facilitate firm insertion and soldering on the printed board and prevent interference sounds when loosening and impacting. Drill a round hole with the same diameter as the microphone in front of the hearing aid box cover to help pick up external audio signals. The hearing aid ear is the key to this device. The ordinary earplugs on the market are not suitable for use as hearing aid headphones for the deaf. Such headphones have poor frequency response and poor sound quality, and can only be used by normal people to listen to radio programs. You should choose the ESC-1 hearing aid earphone launched in China, which is particularly suitable for matching with various models of mid-to-high-end hearing aids at home and abroad. Its frequency range is 300~3400Hz, the typical frequency response is 200~5000Hz; the sensitivity is 110~116dB/mV or more at 1000Hz; the impedance is 700~800Ω. All the components used are miniaturized. The electrolytic capacitor is a CD11 type with a withstand voltage of 6V; the resistance is a 1/16Ω metal mold resistor; the battery is one AA cell. …

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