Automatic Yoghurt Making Using Digital PI for Fermentation Temperature Control

Abstract

It is hard to observe yoghurt making manually in long time period and in a large scale production. Thus, it is crucial to develop a controlling instrumentation that can give a continous yoghurt making process temperature and pH without any human existence as observer. The aim of this project was to build and develop a yoghurt making machine using digital PI to control the fermentation temperature. The system with PIC18F4550 as the main controller will monitor and control yoghurt making process and fermentation temperature 42oC. An experiment is conducted to compare system performance between on-off control and PI control in fermentation process. The system has already set up and develop for yoghurt making process requirement. The PI algorithm to control fermentation temperature at 42oC give better system performance compare to on-off controller. But, noise signal is occured randomly. The pH circuit also has not functioned properly. So, the end process indicator is not develop using pH value as an indicator but using estimated 8 hours time to finish. Keyword: yoghurt, fermentation temperature, Digital PID, phase angle control, PIC18F4550