Revealing the circuit design of smart Bluetooth lighting system - circuit diagrams read every day (57)

　　The lighting system is a subsystem in the smart home and can also be used independently. The lighting system can control various lighting effects in different living areas and occasions to easily solve household energy-saving problems and improve the quality of life. We often encounter this problem in life. When watching TV or reading in the living room, we do not need too strong lighting. We have to turn off the headlights in the living room and turn on other lamps with relatively dark light to meet the needs of watching TV or reading. In order to meet the lighting requirements of different occasions, a variety of lamps need to be installed, which brings great inconvenience to lamp control.

　　Solutions for lighting system control methods are divided into wired methods and wireless methods. Wired methods include X-10 and CEBUS for power line carriers, HomePNA for telephone line methods, IEEE802.3 for Ethernet methods, LONWORKS and IEEE1394 for dedicated bus methods, etc. The advantage of using power lines as the transmission medium for network information is that there is no need to lay additional cables, which reduces the difficulty of construction; the disadvantage is that the transmission rate is only 300Kbps, which is difficult to transmit video and audio signals, has poor confidentiality, and expensive access equipment. Wireless methods include IrDA in infrared mode, IEEE802.11 series in wireless LAN mode, HomeRF in home radio frequency technology, IEEE802.15.1 in Bluetooth, IEEE802.15.4 in ZigBee, etc. The wireless method solves the problem of wiring and can also meet the transmission of video and audio signals. This article introduces a smart home lighting system based on 2.4G radio frequency technology.

　　This solution uses STC12C5A08AD as the MCU controller. STC12C5A08AD is a new generation of microcontroller that adopts the 6th generation security technology. The program cannot be decrypted after being programmed, which enhances the security function. The speed is 8~12 times faster than the ordinary 8051 microcontroller. It has four built-in 16-bit timers and has relatively low power consumption. The control signal of the MCU controls the brightness of the lamp by controlling the thyristor through the optocoupler. A current detection loop is added to the high-current control interface to detect the magnitude of the high-current and is used for detection feedback. The communication method adopts 2.4G wireless communication module, which eliminates the need for wiring, reduces costs, has flexible control methods, wide remote control range, and fast communication speed. This solution can control a total of 12 lamps and is suitable for home lighting control.

　　2.4G Bluetooth module circuit design

　　Common general-purpose chips currently used for 2.4GHz communication include nRF2401 wireless chip module, RFW102 wireless chip module, etc. Based on design requirements and cost considerations, nRF2401 is used for wireless data transmission in this design. nRF2401 is a single-chip wireless transceiver chip that operates in the 2.4GHz ISM band and fully integrates a power synthesizer, power amplifier, crystal oscillator and adjustment circuit. Using QFN24 5×5 mm package, the application circuit uses fewer peripheral components; adopts FSK modulation method, 125 channels, which can meet the needs of multi-frequency and frequency hopping; the transmission rate is up to 1Mbps, with high data throughput; low power consumption, power supply voltage 1.9V~3.6V meets the needs of low-power design; there is a special voltage stabilizing circuit inside the chip, and it has better communication effect using various power supplies including DC/DC switching power supply.

　　Figure 2 2.4G communication circuit

　　Intelligent lighting control circuit design

　　Commonly used dimming methods include: pulse width modulation (PWM) dimming, changing the half-bridge inverter supply voltage dimming, pulse frequency modulation dimming, pulse phase modulation dimming and thyristor phase control dimming. . The phase-controlled dimming method has the advantages of small size, reasonable price and wide dimming power range. This system finally uses thyristor phase-controlled dimming to adjust the brightness of the lamps.

　　Applying the thyristor phase control principle, by controlling the conduction angle of the thyristor, a part of the sine wave voltage input from the power grid is cut off to reduce the average output voltage, thereby controlling the supply voltage of the lamp, thereby achieving dimming. SCR phase-controlled dimming can adjust the voltage of the lighting system quickly and with high dimming accuracy. The dimming parameters can be adjusted in real time in time intervals. Since the dimming circuit is mainly composed of electronic components, it is relatively small in size, light in weight and low in cost. The silicon controlled phase control dimming circuit is shown in Figure 3. The control signal of the microcontroller is inverted by 74HC04 and then sent to the optocoupler MOC3023. After photoelectric isolation, it is input to the control electrode of the thyristor T16C6F to control the conduction angle of the thyristor to achieve dimming.

　　Figure 3 Thyristor phase-controlled dimming circuit

Comments and analysis by the technical editor of Electronic Enthusiast Network:

　　The lighting system based on microcontroller control has the advantages of low cost, short development time, convenient installation and maintenance, and can easily meet the different needs of customers, and has broad market prospects. At present, my country's consumption level is not high, and there is not much demand for large and high-end systems. However, the low cost of lighting systems is becoming more and more widely used in the home market. The lighting system based on microcontroller control introduced in this article has certain market promotion value.