PLC time to counter converter Tcont ladder diagram instruction in LDMicro

Ladder diagram time to counter converter (Tconst) instruction converts the timer value and converts it to a counter value, that will be store in its Tcont constant. 

Tconst Symbol

This instruction has two important parameters- name and delay.

Property setting of Tconst

With a specific PLC cycle time, we can find the counter value as follow,

Tcont Counter = (Tconst delay)/(PLC cycle time)

For example, 

• PLC cycle time = 10 mS
• Tconst delay = 10 ms

Then the Tconst counter = (10 mS)/(10 mS) = 1

Similarly, if we set the Tconst delay = 50 mS then the Tconst counter = 5.

With a typical example, we use a count up counter (CTU) instruction to count an input from a contact. This counter is set to output true whenever it's greater than Tconst. Tconst delay is set to 50 mS, then its counter value is 5 constant.

Timer to counter converter instruction example

With a one shot rising OSR, Tconst run only once at beginning of PLC starting up. X0 is a user input to increase the value of CTU. The CTU will output true whenever it is greater than or equal to Tconst (that is 5).

Xreset is a user input to reset CTU. Click here to download this ladder diagram example.