Dynamic Switch Contact Resistance Detection System
Sponsor: Weicheng Liu, SHFEILI
Team Members: Yuechuan Lin, Yuxin Chen, Jize Hou, Yukang Tian, Wanhao Yu
Instructor: Prof. Chengbin Ma
Prof. Chengbin Ma
As China has achieved great process on the smart grid construction in last few years, low-voltage electrical switches are proved useful in various applications . The number of products is large, while our sponsor SHFEILI is lack of an efficient and accurate way to judge qualification of switches. It becomes our concern to figure out the solution.
Fig. 1 Real Examine Process in SHFEILI
Our goal is to build a compositive embedded system that contains measurement circuit, processor, screen, and various adaptors. While the hardware components are to accurately measure the resistance, the software part will realize our algorithm to determine qualification.
Fig. 2 Detailed Structure
Fig. 3 Concept Rendering
The design contains three major parts: hardware design, circuit design, and algorithm design. Hardware design consists of the component arrangement and dimensions, which proves the user experience and service efficiency. Circuit design is PCB board design of the operational amplifier board to support rapid and accurate measurement. Algorithm design is to produce quick and precise qualify judgement in progress of measurement.
During usage, users choose proper adaptor for switch and assemble it to the main body. Following guidelines shown on the screen, users can finish examination in few seconds.
Fig.4 Exploded View
A python-based code is written into Raspberry Pi our system processor. It controls the measurement circuit, gather data, and apply our algorithm for quality judgement. The following graph shows feedback to user when switch under examine is not approved.
Fig. 5 Feedback User Interface
For measurement current, range and resolution, in the measurement progress, data of the current and range can be collected directly from the PCB board, and by considering the error from the processor and the circuit the resolution can be derived. The sampling rate is determined by the processor and is fixed. The algorithm accuracy should be tested by comparing result with sponsor’s data. Other specifications can be verified using easy experiments.
According to validation part, most specifications can be met.
Measurement Current <= 10 mA
√ Measurement Range @ 1-100 mΩ
√ Resolution <= 0.1 mΩ
√ Sampling Rate >= 1 kHz
√ System Weight <= 1 kg
√ Result Display <= 0.1 s
• Decision-making Algorithm Accuracy >= 95 %
√ means having been verified and · means to be determined.
Our prototype, Dynamic Switch Contact Resistance Detection System, can be used to determine qualification of low-voltage electrical switches with high accuracy and good efficiency. This system provides a solution that satisfies the requirement from our sponsor, SHFEILI, and can improve their examining process.
Sponsor: Weicheng Liu from SHFEILI
Instructors: Chengbin Ma, Main Li and Chong Han from UM-SJTU Joint Institute