Most common manufacturer of plc

 Siemens - Schneider - Panasonic - Allen-Bradley - LG - Delta - Mitsubishi 
 
1- Siemens : 

-   www.siemens.com

2-Schneider :

www.schneider-electric.com

3-Panasonic :

  pewa.panasonic.com/acsd/plc/

4-Allen-Bradley :

 www.ab.com/plclogic

5- LG :

6-Delta :

   www.deltaplc.com

7-Modicon (Schneider) :

www.modicon.com

8-Mitsubishi :

www.mitsubishi-automation.com