Industrial automation control system, application of 3566 current loop isolation interface chip
In the industrial field, when the signal is transmitted between the electrical equipment and instruments that are far away, there is often interference, which causes the system to be unstable and even operate incorrectly. In addition to the influence of internal and external interference in the system, another very important reason is the grounding of various instruments and equipment. Under normal circumstances, the equipment shell needs to be connected to the earth, and the circuit system must also have a public reference ground. However, due to the potential difference between the reference points of each instrument and equipment, a ground loop is formed. The ground loop current will bring common mode and differential mode noise and interference, which often causes the system to fail to work normally.
An ideal solution is to electrically isolate the equipment, so that the originally connected ground wire networks become independent units, and the mutual interference will be greatly reduced.
In industrial automation control systems, instrumentation, and sensor applications, 4-20mA current is widely used to transmit control and detection signals. Because the 4-20mA current loop has strong anti-interference ability and simple circuit, it can be used to transmit analog signals of tens or even hundreds of meters. Generally, if the transmission distance exceeds 10 meters, the current signal needs to be isolated.
The 3566 is a single-chip two-wire isolation interface chip. The chip contains a current signal modulation circuit, a magnetoelectric coupling isolation conversion circuit and a demodulation circuit. Through the magnetic coupling, the energy is transferred from the input line to the output side without requiring Direct electrical connection. The typical value of 3566 nonlinearity is 0.2%, and the temperature drift coefficient is 100ppm, which is suitable for most industrial control and measurement occasions. The input signal of this chip is 4-20mA, and output 4-20mA signal after isolation. The input equivalent resistance of this chip is small, linearity is high, and has a wide input/output creepage distance. Figure 1 is the internal schematic diagram of 3566. Among them, pin 24 is the input current signal inflow terminal, pin 23 is the input current signal outflow terminal, pins 22 and 21 are the zero and full-scale adjustment potentiometer access terminals, and pins 11 and 10 are the output current outflow terminals. Inflow end.
Because all functions are integrated inside the chip, the 3566 is very convenient to use. In practical applications, only a few protection and adjustment components are needed. Figure 2 shows a typical wiring schematic diagram of IDC3516 series chips. The potentiometer RADJ1 connected between pins 22 and 23 is used to adjust the ratio of input current Ii to output current Io. The connection between pins 21 and 22 can be The variable resistance RADJ2 is the bias adjustment resistance of the output current Io. D1, D2 are limiting voltage regulator tubes, used for line surge voltage, lightning protection strong interference, F1, F2 are self-recovery insurance, used for protection of overcurrent in the line. C1 and C2 are filter capacitors, generally 1mF ceramic capacitors can be used, which can filter out high-frequency differential mode interference and reduce the pulsating components of input and output signals.
In the signal transmission, a part of the energy needs to be consumed inside the chip, therefore, the output signal power of the chip is always less than the input power, which is specifically reflected in the voltage drop at the input terminal. Figure 3 is the input characteristic curve of the chip, and the load on the output side is 250Ω. It can be seen that in this case, the signal source needs to have sufficient driving capability (>14V).
Whaylan Portable solar photovoltaic panels use high quality single crystal solar cells with a high conversion rate of 23.5%, further achieving efficient conversion of solar energy to electricity without fear of power shortage. Equipped with high transmittance PET/ETFE membrane packaging, the latest generation of lamination technology and deep embossing process, light and convenient, and with waterproof, dustproof, high temperature resistance, self-cleaning functions, so as to further realize outdoor imagination, endless solar power.
Suzhou Whaylan new energy technology co., Ltd. is located in Suzhou Wuzhong Economic Development zone. It is a new energy conversion electric power equipment, energy storage transformation, energy management, on the basis of independent research and development, production, sales and after-sales service in the integration of high-tech enterprises, business scope covers from grid photovoltaic inverter, energy storage system, off-grid power generation systems and other fields.
3500W power station,Portable Rechargeable Generator 220v,Lighting Solar Energy,Solar Panel Power Station
suzhou whaylan new energy technology co., ltd , https://www.whaylan.com