Core PLC (Programmable Logic Controller) board
For programming the board/microcontroller/pic16f877A pickit 2 programmer is made on the board. Pickit 2 is a programmer by microchip used to program its pic microcontrollers. Pickit 2 uses icsp interface to program the target microcontroller. Icsp interface of pickit 2 programmer is connected with the pic16f877a microcontroller using DIP switches. When ever a new logic is desired to be downloaded in the processor, switch on the dip switches. Dip switches are installed to prevent the controller pins from interference by the pickit 2 programmer circuit. I have a separate tutorial on pickit 2 programmer made at home. Visit the link for more information
Microchip Pickit 2 Programmer made at home – Diy Project
The Resistors on the front side of the pcb that are not aligned are added after the pcb printing. These resistors are added as pull-ups to the input pins. While testing the circuit i found that the input pins of pic16f877 floats so i added the pull-up resistors. On pcb back i added some extra tin/lead on the traces to remove any resistance created in them during the etching process.
Circuit/Block diagram and Pcb of Core PLC board.
PLC status board
Some tutorials that will help you in understanding the interfaces and working of the status board.
Plc Status board Circuit
Ladder logic design and processor selection
Filed Under: Microcontroller Projects, PIC Microcontroller