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Homebrew industrial control PLC using Atmega8

Back in college we had this subject on Programmable Logic Controllers – which is used to control industrial motors, actuators and indicators while collecting input data from sensors? Why use a PLC? Well PLCs are compact, off the shelf, easy to program using Ladder Logic, its much lesser in cost and less power hungry compared to the other means of control while able to control high power instruments and machines. Did I say much less in the previous paragraph? Well it cost less but not cheap – here is a home brew PLC. It doesn’t go in a black box [like the PLCs from Siemens] but it sure do high power control. The main controller of this PLC project is an ATMega8A-P which is rigged to an external EEPROM using I2C bus to be able to hold on more command sequences. The microcontroller is isolated from the high power devices. Inputs are made out of opto couplers – this would enable the microcontroller to sense from sensors that outputs voltages higher/lower than the limits of the AVR. For the output… Continue reading