Now science and technology are developing rapidly, and the microelectronics, wireless, and network technologies are also developing rapidly. At the same time, people's living standards are constantly improving, and the requirements for the safety and convenience of the places where they live are becoming higher and higher. In smart residential buildings, people are more in urgent need of a new type of wireless doorbell product, which can integrate the advantages of reliability, security, convenience and so on, so the design of intelligent voice message doorbell has become a hot spot. The design consists of STC89C52 single-chip microcomputer circuit, 315M wireless module circuit, voice recording and playback circuit, music chip circuit key circuit and power circuit. Wireless data transmission is carried out by the 315M wireless remote control module, which has a long transmission distance and strong anti-interference ability. Outsiders can record voice and leave messages through the recording module. This system has low price, relatively stable performance, wide application range, and very promising market.

Design of Intelligent Voice Message Doorbell Based on Microcontroller

Semiconductor refrigeration was used for heat dissipation of high power LEDs. A practical temperature-controlling system was designed and built with a microcontroller unit( STC89C52) and a thermoelectric cooling module( TEC1-12703) as the core components. Functions including temperature measurement,display,setup,and control were realized. PWM( pulse width modulation)was applied to regulate the driving current of the thermoelectric cooler. Effective refrigeration and temperature control were thus achieved. This system was used for the temperature control of a LED module with the power of 7 × 3 W. When the environment temperature was 22 ~ 25 ℃,the substrate temperature of the LED module could be stabilized in the range of 40 ~ 70 ℃. If the upper and lower temperature limits of the LED substrate were set to be 64 ℃ and 65 ℃,respectively,the power consumed by thermoelectric cooling was only 27% of that consumed by the LEDs. The temperature-controlling system had a high cooling speed( up to 14 ℃ / min) and small temperature fluctuation( only ± 0. 5 ℃). It fulfilled the requirements for LED temperature control and could be used for many other applications.

LI Changguan

Papers

Temperature-controlling system for high power LEDs based on semiconductor coolers