Programmable PLC with various Interfaces

Availability Fig 1 : PLC LCD Display 20×4


Programmable Logic Controllers (PLC) are small computers which perform a number of logic functions in order to process inputs and control outputs. They are used in the industry.

PLC’s normal exist out of a power supply, a central logic control unit and interface modules. they fit in DIN rail cabinets.  They are often programmed using specific Graphic oriented software. 

Availability Fig 2 : PLC PCB

My goal was to develop a PLC existing out of one units having all what most industrial processes need. No extra modules and most interfaces you need. there are no limitations on functionality because it is programmed in “C” language.

This PLC has all the interfaces as described in the table below. The general purpose ports, TS485 and I2C ports are implemented as four wire ports. Each four wire port has two protected micro controller IO lines and a selectable 5Vdc or 12Vdc power.

The photos on the right shows the PCB Display of the PLC. The unit has the following interfaces

Interfaces :

 Description Ports/Interfaces
Power supply 12V 1
General purpose port 2
Analog out 2
Relay No/NC 1
Power output 1A 12V 1
Line Voltage Zero / Peak detector 1
Line power phase cutter 1
USB programming port 1
In Circuit Programming (ICP) 1
IO matrix 1
RS485 Serial port 1
I2C with power port 2

The functions implemented  on this PLC are the following.

Functions :

Availability Fig 3 : PLC+Displ
  Function Values
Controller ATmega 328 
Memory 32K Prog, 2K RAM, 64K EEProm 
Real Time Clock (RTC) 2 ppm accurate timing
Power selection 5Vdc or 12Vdc 
ADC reference 1x
Display LCD 20×4 characters.
 Power protect  Double power input.

The dimensions and other physical characteristics of this PLC are:

Physical Characteristics:

 Description  Values
Case dimension (LxWxH) 110x78x60
Weight 0.3 Kg
Case type DIN rail
Color White / Black
Material Poly-carbonate
Protection Class IP20
Availability Fig 3 : PLC+Displ

The schematics for this PLC was entered in NI-Multi-sim and layout of the PCB was done using NI-Ultiboard. I want to say thanks to national instruments for their support.

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