Design and implementation of digital current loop device for frequency converter
Dang, Yen (2024)
2024
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Julkaisun pysyvä osoite on
https://urn.fi/URN:NBN:fi:amk-2024112129246
https://urn.fi/URN:NBN:fi:amk-2024112129246
Tiivistelmä
This thesis focuses on the design and implementation of a digital current loop device for a frequency converter to serve as an intermediate device between the motor and the frequency converter. In addition, this current loop device has an advanced feature of fast and slow increments or decrements, which is very convenient and user-friendly for users.
The work methods for this project were split into three main stages: circuit design and prototyping, Arduino software development and manufacturing the physical Printed Circuit Boards (PCB) for the digital current loop device. The expected inputs such as torque (Nm) and speed (rpm) values were fed into a rotary encoder and were displayed on an LCD I2C screen simultaneously. Then, the digital inputs for the torque (0 – 50 Nm) and for the speed (0 – 3000 rpm) were converted into the 0 – 20 mA current loops through DACs connected to the Arduino Nano board. In addition, the prototype measurement was divided into four main parts: Filter, Digital Signal Processing, Digital Analog Converter (DAC) and Analog to Digital Converter (ADC). These individual circuits on breadboards were verified with the software program simultaneously to achieve the accurate outcomes before integrating them together.
The results from the integrated PCBs were consistent with the individual circuit initially tested on the breadboards. Consequently, the desired torque and speed values showed positive correlations with the corresponding current values ranging from 0 – 20 mA. The finished device was assembled by placing PCBs into two metal boxes connected via CAT6 cable. To ensure accuracy and eliminate the capacitive crosstalk issue and frequency interference, signal wires were paired and proper grounding and shielding techniques were implemented. These measures were crucial for maintaining signal stability in potentially noisy environments, ultimately enhancing the accuracy of the 0 – 20 mA current loop outputs.
The work methods for this project were split into three main stages: circuit design and prototyping, Arduino software development and manufacturing the physical Printed Circuit Boards (PCB) for the digital current loop device. The expected inputs such as torque (Nm) and speed (rpm) values were fed into a rotary encoder and were displayed on an LCD I2C screen simultaneously. Then, the digital inputs for the torque (0 – 50 Nm) and for the speed (0 – 3000 rpm) were converted into the 0 – 20 mA current loops through DACs connected to the Arduino Nano board. In addition, the prototype measurement was divided into four main parts: Filter, Digital Signal Processing, Digital Analog Converter (DAC) and Analog to Digital Converter (ADC). These individual circuits on breadboards were verified with the software program simultaneously to achieve the accurate outcomes before integrating them together.
The results from the integrated PCBs were consistent with the individual circuit initially tested on the breadboards. Consequently, the desired torque and speed values showed positive correlations with the corresponding current values ranging from 0 – 20 mA. The finished device was assembled by placing PCBs into two metal boxes connected via CAT6 cable. To ensure accuracy and eliminate the capacitive crosstalk issue and frequency interference, signal wires were paired and proper grounding and shielding techniques were implemented. These measures were crucial for maintaining signal stability in potentially noisy environments, ultimately enhancing the accuracy of the 0 – 20 mA current loop outputs.