The concept of smart home and Internet of Things is gradually gaining popularity. More and more users hope that they can use electricity clearly and safely. Energy-saving and environmentally-friendly smart sockets that measure electrical energy consumption and other parameters are becoming the new favorite of the family. This paper introduces a design scheme of metering socket based on CSE7759 energy metering chip of Core Technology Co., Ltd. This program can measure the power parameters such as voltage, current, power and power of power equipment, and is equipped with LCD display. Electricity parameters. The program also has the function of automatically cutting off the power automatically.
First, the system design
The measuring socket hardware circuit mainly includes: energy metering, MCU control, liquid crystal driving, relay control, power supply voltage regulator circuit, as shown in the following figure.
Second, detailed design
2.1, energy metering circuit
The voltage sampling collects the signal on the zero line. The maximum input signal of the CSE7759 voltage sampling input pin is ±700mV. The input signal of the 1M and 1K resistor network is about 220mV, which meets the input requirements. The current sampling is completed by collecting the current on the live wire, and the current is converted into a voltage signal through the manganese copper resistor. The maximum input differential signal of the CSE7759 current input pin is ±43.75mV. In theory, the larger the sampling signal is, the higher the measurement accuracy is but the manganese copper is selected by the resistor. If the size is too large, the power consumption will be too large. For the specific selection, refer to the table below.
2.2, pulse count
The voltage and current signals are converted into pulse signal output by CSE7759, the CF pin output pulse frequency indicates the active power value, and the CF pin outputs the pulse frequency. When the SEL pin is high, the voltage is valid, when the SEL pin is low. The level indicates the current rms value. The MCU counts the output pulses of CF and CF1 by timing for a certain period of time, calculates the pulse frequency, and then calculates the actual value by the formulas (1), (2), and (3). Taking the voltage calculation as an example, assuming that the measured voltage value is U, and the measured pulse frequency is FU=1260 Hz, there are: 1260 Hz=(U/1001×2)/2.43V×3579000 Hz/512, which is calculated as U=219.2V. In addition, the CSE7759 voltage The current RMS has an accuracy of ±0.5% in the range of 500:1, and the active power has an accuracy of ±0.2% in the range of 1000:1, which fully satisfies the measurement of general electrical equipment parameters.
Note: V1 and V2 are voltage and current sampling signals respectively, Fsoc is built-in crystal oscillator, 3.579MHz, Vref is built-in reference voltage, 2.43V.
2.3, measurement correction
Due to the differences between devices, each metering socket parameter may not be exactly the same, so the metering correction problem is involved. The following is a description of the calibration method using voltage correction as an example.
1 Add the standard voltage U=220V, according to the formula Fu=(V1×2)/Vref×Fosc/512, calculate the theoretical value of the output pulse as Fu=1264.5Hz.
2 Measurement and measurement circuit CF1 output pulse frequency, if Fu'=1000Hz, and the theoretical value ratio L≡1264.5/1000=1.2645.
3 Store L in EEPROM. During the actual test, the voltage pulse frequency is measured as F, then the correction should be F'=F*L, and then the actual voltage value can be calculated according to formula (1).
Third, summary
The CSE7759-based metering socket can meet the needs of measuring the electrical parameters of everyday household appliances. In addition, CSE7759 has the advantages of small size (SOP8 package), built-in oscillator, simple peripheral circuit, high precision, low power consumption (working current <3mA), etc. It is a good choice for energy metering chips in smart sockets and home appliance metering modules.
Moving head beam light
Well and hight quality control
New design products
Customers design and Logo are welcomed
Quickily delivery
Competitive prices
Fit for gifts and premiums
sample can be available
OEM acceptable
Years of exporting experience as professional stage lighting manufacturer:
Senior R&D technical staff with 7 years experience in stage lighting industry;
Strict quality control in producing to maintain reliable quality;
Provide cost-effective products, wholesale price;
Professional sales team to provide perfect service.
Our company have 13 years experience of LED Display and Stage Lights , our company mainly produce Indoor Rental LED Display, Outdoor Rental LED Display, Transparent LED Display,Indoor Fixed Indoor LED Display, Outdoor Fixed LED Display, Poster LED Display , Dance LED Display ... In additional, we also produce stage lights, such as beam lights Series, moving head lights Series, LED Par Light Series and son on...
Moving Head Light Series,Beam Moving Heads Light,Beam Moving Light,Moving Head Light Beam
Guangzhou Chengwen Photoelectric Technology co.,ltd , https://www.cwstagelight.com