Eggshell Crack Detection System Design Based On DSP

Removing cracked eggs is an important procedure for guaranteeing quality of processing eggs and reducing cost. At present, China mainly relies on testing workers under observation in the lights or turn with mutual collision, listen to the voice of eggshell, and other methods to identify and remove cracked eggs, this approach is inefficient and require large amounts of manpower, therefore, study on high-speed, high efficiency, high-precision automated detection of broken eggs is an inevitable trend in modern Egg detection technology.In this task, first we analyzed the egg's phonating mechanism when it is knocked by a small rubber bead. An intact egg and a cracked egg don't phonate similarly because of different structures. According to this characteristic, in this paper, an eggshell crack detection system was designed based on DSP. The system contains the following modules: sound collecting, signal amplifying, band-passed filtering, analogy to digital conversion, serial port communication, LCD display. Using this system, we could collected the sound signals of knocking eggshells and uploaded them which were separated into a digital signal to a PC for processing through the DSP and PC serial interface.Based on digital signal processing technology and using MATLAB software, a large numbers of experimental data on access were analyzed through power spectrum. By this means we could found out the differences between intact egg's sound signal and cracked egg's sound signal in frequency field, then regarded their average and extreme differences of the power spectrum area and the first resonance peak amplitude as the discriminant factors, at last, we established the discriminant function to distinguish intact eggs and cracked eggs based on Bayes discrimination principle.In software design, we programmed the procedure of detecting cracked eggs based on DSP with C language and assembly language. The system software includes the main program and interrupt service program. In the main program, the DSP is always waiting for knocking eggs. Once the knock happened, the program entered the interrupt service program, in which the system began to sample, storage and process the signals of knocking eggshells, at last, the results were displayed through LCD. In addition, in order to communicate with PC, we programmed a serial communication procedure by VC++ software.In this paper, we chose DSP as the core of the system, which processes fast, and has high efficiency, lower costs, in order to achieve the function that once an egg was knocked it started to simple signal, we adopted the threshold circuit to check the signal's section start, and it could provide a sort of Hardware platform for the online test of cracked eggs.