ABB PLC Counter : CTU, CTD and CTUD

ABB PLC have up counter CTU, Down counter CTD and up down counter CTUD. counter increment or decrement counter current value when input of counter is changed from false to true or OFF to ON. each change of counter input increment or decrement by value 1 of counter current value. counter preset value is a numerical value for counter range. counter are used to count input bits changes. range of counting bit is declared in preset value. counter range is fixed

ABB plc Up Counter CTU

up counter is incremental counter when input of counter is changed from false to true than counter increment by 1 to reached preset value of counter. once counter reached to preset value than output of counter Q is turned on. Following are input and output for up counter

input of up counter
• CU : up counter, bool data type each change of CU increment counter by 1
• Reset : reset input of counter when reset is true than counter reset.
• PV : counter preset value. maximum value of counter to count bit.
output of counter
• Q : output bit of counter. state of Q is true when counter CV is equal or greater than preset value.
• CV : output of counter. it is a current value of counter.

above is the example of up counter in abb plc. each rising edge of CU increment counter by 1 when counter value(CV) is equal or greater than preset value than output of counter (Q) is turned on. up counter reset current value (CV) to zero if the counter reset input is turned on. counter current value continue increment even counter output is true.

ABB plc Down Counter CTD

CTD is down counter of abb plc when each rising edge of down counter decrement counter value by 1. when counter initialize or first time run counter preset value is not set until counter load input is false, so make load input true to set preset value. when load input is turned on counter preset value is set and each change of counter input decrement counter value 1. following are the down counter input and output

input of up counter
• CD : down counter input, bool data type each change of CD decrement counter by 1
• LOAD : when load is set to true than counter preset value is set. other wise counter not decrement.
• PV : counter preset value. counter preset value set when load is true.
output of counter
• Q : output bit of counter. state of Q is true when counter CV is equal to zero.
• CV : output of counter. it is a current value of counter.

above is the example of down counter in abb plc.

• set load to true so counter preset value is set than set load false. if load is true and counter input is changed (CD) from false to true than counter current value remain unchanged so always set load value false if the counter preset value is set. if the counter value is set and load input is false than each rising edge of counter CD input decrement counter CV value by 1 when untill counter value is reached to zero. once counter value is zero than counter output Q is set to true.

ABB plc UP and Down counter CTUD

CTUD is up down counter instruction in abb plc. CTUD works as up and down counter when proper input of CTUD is selected. for UP counter CU is set to true and all other bit input set to false. for down counter CD bit is turned on and preset value set. CTUD is combination of up and down counter it operates up or down counter. each rising edge of CU input counter increment by 1 and each rising edge of CD counter decrement value by 1.

above is the example of up down counter in abb plc. all inputs and outputs are combination of both up and down counter. Up down counter work as up counter if CD, load, reset is set to false and counter CU input is changed from false to true than counter increment value by 1. QU is output of up counter it set when counter (CV) is greater than counter preset value. up down counter operate as down counter when CU, RESET and load is false and preset value is set or counter current value is greater than zero. each rising edge decrement counter value by 1.QD is output of down counter it turned when counter current value is equal to zero.