A method for extracting a stable clock from an indoor LED lighting signal

Abstract

The application discloses a method for extracting a stable clock from an indoor LED light signal, characterized in that a photodiode is used as a photoelectric detector to receive a light signal emitted by an indoor LED lamp, then photoelectric conversion is performed on the light signal to obtain a current signal, the current signal is subjected to current-voltage conversion and voltage amplification to obtain a low-voltage power distribution network double-frequency signal containing a direct current component and high-frequency noise, through band-pass filtering processing, setting of a voltage reference and a voltage comparator, a sinusoidal 100Hz clock signal extracted can be optionally shaped into a 100Hz square wave signal, which is used as a reference signal for calibration of a physical clock of a wireless sensor network node. The circuit is simple in implementation, the extracted sinusoidal and square wave clock signals have clear waveforms, and the frequency is accurate and stable.

Description

Technical Field

[0001] This invention belongs to the field of signal reception and analysis processing technology, and relates to a method for generating a reference clock for wireless sensor networks, specifically a method for extracting a stable clock from indoor LED illumination signals. Background Technology

[0002] Wireless sensor networks (WSNs) are self-organizing networks comprising numerous sensor nodes. These nodes typically communicate and collaborate to sense and collect information about various monitored objects within the network's coverage area in real time, process this information, and then transmit it to end users. WSNs are currently widely used in defense, industrial monitoring, and smart homes.

[0003] In a wireless sensor network with specific functions, consistent timing among different sensor nodes is essential for their collaborative operation. Tasks such as data tagging, coordinated sleep, and data fusion all require clock synchronization among sensor nodes. The prerequisite for clock synchronization in a wireless sensor network is that the clocks of each node are sufficiently accurate and stable. Accurate and stable sensor node clocks effectively reduce the frequency of clock synchronization, avoiding significant power consumption losses caused by frequent synchronization, thereby improving the data acquisition and processing capabilities and survivability of the wireless sensor network.

[0004] Methods for solving clock synchronization in wireless sensor networks generally fall into two categories. One category uses clock synchronization protocols such as RBS, TPSN, and FTSP to achieve virtual clock synchronization between nodes through software adjustments. The other category uses a common external clock signal as a reference to uniformly calibrate the physical clocks of all sensor nodes.

[0005] To maintain high efficiency and low loss, low-voltage power transmission and distribution in daily life typically uses alternating current (AC) mode, such as AC 220V / 50Hz. This AC signal has a precise and stable period or frequency. Furthermore, the precise and stable periodic fluctuations of AC power can be transmitted remotely through power transmission and distribution equipment, and can even be reflected in light signals through LED lights. Summary of the Invention

[0006] The purpose of this invention is to provide a method for extracting a stable clock from indoor LED illumination signals.

[0007] To achieve the above objectives, the present invention adopts the following technical solution:

[0008] A method for extracting a stable clock from indoor LED illumination signals is characterized by using a photodiode as a photodetector to receive the light signal emitted by the indoor LED lights, then performing photoelectric conversion on the light signal to obtain a current signal, and then performing current-to-voltage conversion and voltage amplification on the current signal to obtain a low-voltage power distribution network signal with twice the power frequency, containing DC components and high-frequency noise. After bandpass filtering and setting a voltage reference and voltage comparator, the extracted sinusoidal 100Hz clock signal can be selectively shaped into a 100Hz square wave signal as a reference signal for physical clock calibration of wireless sensor network nodes.

[0009] According to the present invention, the photodiode is a Hamamatsu diode S6968.

[0010] Specifically, the current-to-voltage conversion and voltage amplification use the OPA2330 chip.

[0011] The bandpass filtering process uses the AD8616 chip, with its center frequency set to 100Hz, stopband set to 80Hz, passband set to 20Hz, and Q value not less than 4.5.

[0012] The voltage comparator uses the AD8616 chip.

[0013] The voltage reference uses the TL072 chip.

[0014] The present invention provides a method for extracting a stable clock from indoor LED illumination signals. This method uses photoelectric conversion, amplification and filtering, and voltage comparison to extract a low-voltage power distribution network frequency signal (twice the power frequency of the network) as a reference signal for physical clock calibration of wireless sensor network nodes. The circuit implementation is simple, and the extracted sine and square wave clock signals have clear waveforms and accurate and stable frequencies. Attached Figure Description

[0015] Figure 1 This is a block diagram illustrating the method for extracting a stable clock from indoor LED illumination signals according to the present invention.

[0016] Figure 2 This is a circuit diagram illustrating the method for extracting a stable clock from indoor LED illumination signals according to the present invention.

[0017] Figure 3 It is the signal waveform after photoelectric conversion and amplification.

[0018] Figure 4 This is a test diagram showing a sinusoidal clock signal output from the SMA1 port.

[0019] Figure 5 This is a test diagram showing a square wave clock signal output from the SMA2 port.

[0020] Figure 6 It is the frequency distribution of the extracted clock signal.

[0021] Figure 7 It extracts the relationship between the clock signal strength and the distance to the LED.

[0022] Figure 8 It is the stability of the extracted clock signal.

[0023] The present invention will now be described in further detail with reference to the accompanying drawings and embodiments. Detailed Implementation

[0024] The applicant discovered through research that, for indoor applications of wireless sensor networks (such as indoor positioning, smart homes, and workshop scheduling), a stable clock extracted from indoor LED lighting signals can serve as a reference signal for the physical clock calibration of wireless sensor networks.

[0025] See Figure 1 This embodiment provides a method for extracting a stable clock from indoor LED illumination signals. A photodiode is used as a photodetector to receive the light signal emitted by the indoor LED lights, perform photoelectric conversion to obtain a current signal. After current-to-voltage conversion and voltage amplification, a low-voltage power distribution network signal at twice the power frequency, containing DC components and high-frequency noise, is obtained.

[0026] To obtain an accurate and stable low-voltage power grid signal at twice the power frequency, bandpass filtering is also required.

[0027] In addition, to improve the flexibility and availability of the extracted clock signal in the physical clock calibration of wireless sensor network nodes, a voltage reference and voltage comparator are designed to selectively shape the extracted sinusoidal 100Hz clock signal into a 100Hz square wave signal.

[0028] Figure 2 A circuit diagram for implementing the above method is provided, including:

[0029] (1) The photodetector can obtain signals from LED illumination, specifically using Hamamatsu diode S6968. Diode S6968 is connected to U1, the output of U1 is connected to U2 through C2 and R2, the output of U2 is connected to U3 through R4 and C4, the output of U3 is connected to U5 and outputs SMA1, and the output of U4 is connected to U3 and U5 respectively.

[0030] The S6968 diode outputs a current signal. An OPA2330 chip is used as U1 for current-to-voltage conversion and as U2 for voltage amplification. See [link to relevant documentation] for the signal waveforms after photoelectric conversion and amplification. Figure 3 .

[0031] (3) The low-voltage distribution network signal obtained after current-to-voltage conversion by U1 and voltage amplification by U2 contains DC components and high-frequency noise. The AD8616 chip is used as U3 to design a bandpass filter with a center frequency of 100Hz. At the same time, to prevent 50Hz power frequency interference, the stopband is set to 80Hz, the passband to 20Hz, and the Q value is not less than 4.5.

[0032] (4) To improve the flexibility and availability of the extracted clock signal during physical clock calibration of wireless sensor network nodes, the TL072 chip is used as the 1.65V voltage reference in the U4 design. The AD8616 chip is used as the voltage comparator in the U5 design. The extracted sinusoidal 100Hz clock signal (output from SMA1) can be optionally shaped into a 100Hz square wave signal (output from SMA2).

[0033] Experimental test:

[0034] A standard commercial LED light (Kangshio, 36W, 6500K white light) is directly connected to the indoor lighting grid (AC220V / 50Hz) for experimental testing. The hardware circuit designed in this example ( Figure 2 The sine and square wave clock signals extracted at a distance of 3 meters from this ordinary commercial LED light are as follows: Figure 4 and Figure 5 As shown, the waveform is clear, and the frequency is accurate and stable. Figure 6 The test results for the extracted clock signal frequency distribution show that the center frequency is 100Hz and exhibits a normal distribution. Figure 7 The extracted clock signal strength and the distance relationship with the LED light show that, within a 7m distance range, the hardware circuit designed in this embodiment ( Figure 2 They can all reliably receive the aforementioned clock signal. Figure 8 The Allan variance stability test results for the extracted clock signal show a long-term stability of 9.5 × 10⁻⁶. -8 / week, exceeding the long-term stability of ordinary crystal oscillators, can be used as a reference signal for physical clock calibration of wireless sensor network nodes.

Claims

1. A method of extracting a stable clock from an indoor LED lighting signal, characterized in that, The photodiode is used as a photoelectric detector to receive the light signal emitted by the indoor LED lamp, and then the photoelectric conversion is performed on the light signal to obtain a current signal, the current signal is converted from current to voltage and amplified in voltage to obtain a low-voltage power distribution network two times power frequency signal containing a direct current component and high-frequency noise, the band-pass filtering processing is performed, and the voltage reference and the voltage comparator are set to shape the extracted 100Hz clock signal in a sine form into a 100Hz square wave signal as a reference signal for calibrating the physical clock of the wireless sensor network node; The photodiode adopts a Hitachi diode S6968; The current-voltage conversion and voltage amplification adopt an OPA2330 chip; The band-pass filtering processing adopts an AD8616 chip, the center frequency is set to 100Hz, the stopband is set to 80Hz, the passband is 20Hz, and the Q value is not less than 4.5; The voltage comparator adopts an AD8616 chip; The voltage reference adopts a TL072 chip.

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