PLC WIRING CONNECTION - TUTORIAL 2

How to do wiring connections in PLC?

Most of PLC has the same wiring connection. so, here I take 
Allen Bradley Micrologix 1400 wiring connection

• Input - Vdc   (DC input +24Vdc or 0Vdc)
• Output - Vac dc (DC and AC both output)
• Input/Output- 20/12 = 32 

                                   

1) Power supply wiring connection to PLC

• most of PLC have there own power supply module cards which acts as a SMPS to provide supply to the rack, which in turn supply to different cards (AI, AO, DI, DO, RTD, etc).

• Generally, the power module requires 220V AC or 24v DC which converts into the required supply voltage for the cards, which is typically 24V dc, 12V dc, 5V dc.

• so, basically to power -up the PLC need 220V ac supply or 24V dc supply which can be given by SMPS 

     

 Digital input module: typical input to these modules is 24V   dc, 115Vac,230V AC
 Ex: switches, pushbuttons, relays, pumps

Analog input module: typical input to these modules in 4-20mA, 0-10V, ohms, mv 
Ex: pressure, flow, level transmitter, RTD(ohm), thermocouple(mv)

• Here, PLC require 24V dc 

• SMPS convert phase voltage to 24V dc

• The output of SMPS 24V dc and 0V dc directly connected with the PLC  +24vdc and Vdc neutral

• this wiring connection is shown in the above figure 

2) Push-button, limit switch (Input) wiring connection 

• PLC input require +24Vdc or 0 Vdc  

• If +24V dc apply to IN0(input) then 0V dc apply to COM0 through SMPS

• and if 0Vdc apply to IN0 then +24 Vdc apply to COM0 through SMPS

• In short, it will make +24Vdc to 0Vdc loop between input and common of the PLC

• The push button and limit switch wiring connection shown in the below figure.

3) PNP and NPN sensor wiring diagram 

PNP ----------- Positive(+) ---------  +24V dc

                      Negative(-) ----------     0V dc

                      Control(+) ------------ +24V dc 

                      Common ----------------  0V dc

NPN ----------- Positive(+) ---------  +24V dc

                      Negative(-) ----------     0V dc

                      Control(-) ------------     0V dc 

                      Common ------------- +24V dc

• As we can see in the above figure, both the transistor have their different control   

• If we connect both sensors at a time we should have a different commons 

• Thus all input have their separate common 

• The separation of common according to the input as follows

• If common have +24Vdc than inputs must have 0Vdc

• If common have 0Vdc than inputs must have +24Vdc

4) Output wiring connection

• Here, Vac dc0 link with OUT0 and Vac dc1 link with OUT1
• both are relay type output 
• it may give either 220V phase or 24V dc 
• Vdc2 link with OUT2, OUT3, OUT4, OUT5, OUT6, OUT7 and COM2
• these all are transistor type output. it only works on +24Vdc/0Vdc according to Vdc2 voltage  
• these connection shown in above figure