Large Open Source PLC Components and Source Files

Created on: 23 April 2013

Components used to construct the Large Open Source PLC including case, boards and connectors. Schematic diagrams and photos of all the circuit boards used in the large brick open source PLC.

Large Open Source PLC Circuit Boards

The Large Brick Open Source PLC (OSPLC) consists of three circuit boards:

• CPU Board – contains the microcontroller, RTC and other ICs.
• IO Board – contains the power supply regulator, optically isolated input and output circuitry and connectors.
• Status Board – input indicator LEDs, reset switch, status LED and USB connector.

Design Source Files for the Large Open Source PLC

The boards were designed using Altium designer. The download below is for the Altium designer source files for the three boards used in the PLC.

For schematic diagrams and board outlines in PDF format for each board, see the sections below.

Download the Altium designer PLC source files: OSPLC2_2.zip (795.7kB) – needs the Altium designer software to view. Also contains Gerber files and drill files.

Large Open Source PLC CPU Board

The PLC CPU board is mounted on the IO board with two rows of pin headers. On the top of the IO board is the AT91SAM7A3 microcontroller that is the main controller of the PLC.

A REF2930 voltage reference IC, 18.432MHz quartz crystal, AT24C128N EEPROM, M41T00 RTC (real-time clock) IC, MAX3232EI IC, ST3485EC RS485 IC and LM75AD temperature sensor IC are all found on the top side of the IO board.

CPU board schematic: OSPLC2_2_CPU.pdf (37.9kB)

CPU board outline and dimensions: OSPLC2_2_CPU_outline.pdf (276.4kB)

The RTC backup battery can be seen on the bottom of the IO board, as well as the SD card socket.

Large Open Source PLC IO Board

The I/O board has components mounted on both sides of the board.

I/O board schematic: OSPLC2_2_IO.pdf (75.8kB)

I/O board outline and dimensions: OSPLC2_2_IO_outline.pdf (113.3kB)

Large Open Source PLC Status Board

The open source PLC status board contains indicator LEDs for the PLC inputs. It also has a reset switch, status LED and USB port. Silkscreen markings on the status board mark the input and output connections.

Status board schematic: OSPLC2_2_Status.pdf (15.1kB)

Status board outline and dimensions: OSPLC2_2_Status_outline.pdf (33.4kB)