UP and Down counter using example

Application:-Understand the concept of CTUD (count up and down) counter instruction in the PLC. Explain CTUD counter concept using PLC program.

Components:-Programmable logic controller, two lamps (24 VDC).

Explanation:-

CTUD counter is the combination of UP counter and down counter. This counter will work on both the function count UP and count down. Take two lamps to understand the concept of CTUD counter. In this UP function will operate L1 and down counter will operate L2.

PLC program:-

Write the ladder program for above application using ladder diagram language. Here for ladder logic we can use any supported PLC system like S7-1200, S7-300, S7-1500 or any other PLC which can support this instruction. For PLC logic we need digital inputs and outputs.

Digital inputs:-

UP button=I0.0

Down button=I0.1

Reset Button=I0.2

Load Button=I0.3

Digital Output:-

L1=Q0.0

L2=Q0.1

PLC program Explanation:-

In network 1, we have used CTUD counter to understand the concept,

Here CU is for counter UP, CD is for counter down, R is reset input and load is for load input. QU is the output of UP counter and QD is the output of down counter.

So if UP button is pressed, counter will start to count up and CD is pressed counter will count down.

If R is pressed then UP counter value reset and if LD is pressed then PV will be load.

If CV value is equal to PV value or greater than PV value, L1 (Q0.0) will be ON.

If CV value is less the or equal to zero, then L2 (Q0.1) will be ON.