Intelligent lighting control solution

1. Overview   
         
Smart home takes home as the platform, and uses computer technology, digital technology, network communication technology and integrated wiring technology to organically combine various subsystems closely related to family life, such as anti-theft alarm system, home appliance control system, network information service system, etc.

Through the central management platform, home life can be comfortable, safe, convenient, energy-saving, healthy and environmentally friendly. Similar names include digital home, digital garden, network home, home automation, E-HOME, etc. 
         
At present, smart home can provide users with home security alarm, video intercom, home appliances, lighting dimming, indoor and outdoor remote control of equipment, telephone remote control, INTERNET remote control and other functions. Product types include wired, wireless or wired and wireless combination. Wireless mode has the advantages of no wiring, mobility, easy installation and wide application occasions, and gradually becomes the mainstream of application.  
  
2. Solution design   
         
Beneng Technology has developed a series of smart home solutions using IAI's wireless series chips combined with MICROCHIP's PIC series microcontrollers, such as water and gas wireless meter reading solutions for residential areas, wireless switch solutions for home terminals, wireless lighting control solutions, QVGA solutions for large-screen interfaces of terminal controllers, terminal INTERNET access solutions, etc. IAI's wireless chip series has the characteristics of high integration, few peripheral components, low power consumption, stable and reliable performance, etc. The chip integrates all the functional modules necessary for FSK wireless transceiver, including multi-sideband PLL synthesizer, PA, LNA, mixer, baseband filter, intermediate frequency amplifier, signal strength indicator RSSI, data quality detection DQD, battery voltage detection, AFC and microcontroller, etc. At the same time, MICROCHIP's PIC series chip microcontroller has the characteristics of low power consumption, high stability and good anti-interference. For this reason, our company has developed two small communication modules PHY and EV-IA4421-433M-3 using IA4421 chip, which can provide users with serial port or SPI interface, which is convenient for users to use and develop.  
         
This article introduces an intelligent lighting control solution from both software and hardware aspects. The solution is divided into two parts: handheld RF remote control and lighting control. The home lighting brightness adjustment, full on and off, timing control and soft start functions can be realized through handheld devices. 

2.1 Hardware composition framework of lighting control part The  

       hardware composition block diagram of lighting control part is shown in Figure 1, where the interface circuits of each part are as follows: 


Figure 1 Wireless lighting control


circuit Figure 2

Non-isolated power supply circuit diagram ① The non-isolated power supply circuit provides the working voltage for MCU and wireless module, as shown in Figure 2, using PI's LinkSwitch-TN. Since the power MOSFET and controller are integrated in one IC, the design process can be greatly simplified. The number of components used in the circuit is very small, and no transformer is required, that is, the quick design part can be used to complete the design of common output voltage and current using standard components.  
         
② The wireless module connection circuit is shown in Figure 3. PHY only needs to use 5 I/O ports to work, and uses SPI compatible control interface as the data communication interface. Our test board is also connected to the PHY module in this way. The functions of each interface are as follows: SCK: SPI serial port clock input; SDI: SPI serial port data input; NSEL: SPI chip select input (low level is valid); SDO: SPI serial port data output; NIRQ: interrupt request output (low level is valid); PHY module is used as data. The module has the advantages of small size and low power consumption, and is very suitable for use in wireless devices. 


Figure 3 Wireless module connection circuit

③ The dimming module circuit is shown in Figure 4, including an EMI filter, a passive power factor correction, ballast control and lamp resonant output stage. The output stage adopts PWM output drive signal, drives the half-bridge MOS tube through the drive transformer, and realizes the control of the light. 


Figure 4 Dimming control circuit

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2.2 Hardware composition framework of handheld RF remote control  
         
The hardware composition framework of handheld RF remote control is shown in Figure 5, and the specific circuit interface is shown in 


Figure 6. Key circuit

① The key circuit is shown in Figure 6.                              
4*4 light touch keys are used as user input. The user key input judgment adopts the ordinary I/O method. The specific definition of each key can be determined according to the design needs of the developer.                                         
② The wireless module connection circuit is basically the same as the handheld RF wireless module circuit and the lighting control part. The circuit is shown in Figure 3. Both use the SPI method to communicate with the wireless module. 
③ The power supply circuit is shown in Figure 7. The handheld remote control uses 5V~9V dry batteries to power the system. 


Figure 7 Power supply circuit

2.3 Lighting control software composition framework  
         
The software flow is shown in Figure 8, which is divided into system initialization, main loop flow and interrupt service program. The function descriptions are as follows:  
         
① MCU initialization function: including MCU timer setting, PWM setting, interrupt setting and input and output settings of each I/O port, etc.  
         
② IA4421 initialization: set each register of IA4421, including frequency, transmission rate, transmission power, frequency deviation and other settings.  
         
③ Main loop program: mainly includes the detection of wireless signals and the detection of working current and voltage.  
         
The main loop program is the basic control part of the software. It is an infinite loop program. Through this series of management functions, it continuously detects the occurrence of events and performs corresponding functional operations. It contains many subroutines, such as: Check if it's time to execute events (timer time event processing), communication handshake recognition, address recognition, PWM output processing, current and voltage sampling processing, power management, etc. 


Figure 8 Software Flowchart

2.3 Handheld RF remote control software composition framework  
        
The software flow chart is shown in Figure 9. The software system includes: MCU initialization, variable initialization, IA4421 initialization, and main program loop detection. 

The main loop program includes user key input detection, wireless data transmission, wireless signal reception and feedback data processing, correctly sending user input information and timely feedback of the lighting control status to the handheld device, so that the user can see it at a glance.


Figure 9 RF remote control software flow chart

3. Summary  
         
The intelligent lighting control solution introduced in this article can be used in any smart home design solution and can be easily applied to various smart home systems.