PLC Programming
  • Home
  • PLC Forum
  • Contact Us
  • PLC & HMI
  • Electric & Electronic
No Result
View All Result
PLC Programming
  • Home
  • PLC Forum
  • Contact Us
  • PLC & HMI
  • Electric & Electronic
No Result
View All Result
PLC Programming
No Result
View All Result

Count Down (CTD)

Count Down (CTD)
Share on FacebookShare on Twitter

RelatedPosts

PLC Ladder Diagram

How to learn plc programming and plc software

User Defined Datatype UDT Usage Examples in RSLogix 5000 PLC

The CTD instruction counts downward each time the rung-condition-in transitions from false to true.

Ladder Diagram
Operand Data Type Format Description
Counter COUNTER tag Counter structure
Preset DINT immediate Value of Counter.PRE.
Accum DINT immediate Value of Counter.ACC.
COUNTER Structure
Mnemonic Data Type Description
.CD BOOL The countdown enable bit contains rung-condition-in when the instruction was last executed.
.DN BOOL The done bit when clear indicates the counting operation is complete.
.OV BOOL The overflow bit when set indicates the counter incremented past the upper limit of 2,147,483,647.
.UN BOOL The underflow when set indicates the counter decremented past the lower limit of -2,147,483,648.
.PRE DINT The preset value specifies the value which the accumulated value must reach before the instruction indicates it is done.
.ACC DINT The accumulated value specifies the number of transitions the instruction has counted.

 

When rung-condition-in is set to true and .CD is false, .ACC will be decremented by one. When rung-condition-in is false, .CD will be cleared to false.

plc programming rungcd plc

plc programming ctdflow plc plc programming ctdflowtrue plc plc programming ladderctd plc

A conveyor brings parts into a buffer zone. Each time a part enters, limit_switch_3 is enabled and counter_2 increments by 1. Each time a part leaves, limit_switch_4 is enabled and counter_2 decrements by 1. If there are 100 parts in the buffer zone (counter_2.dn is true), conveyor_A turns on and stops the conveyor from bringing in any more parts until the buffer has room for more parts.

Tags: CTDinstructionLadder
Previous Post

RsLogix Emulate

Next Post

Siemens TIA (Totally Integrated Automation) Portal

Related Posts

PLC Controller Firmware Upgrade
PLC & HMI

PLC Controller Firmware Upgrade

Connect to PLC via USB cable
PLC & HMI

Connect to PLC via USB cable

PLC First Scan Bit
PLC & HMI

PLC First Scan Bit

Siemens PLC Programming, S7-300 and S7-400 (SIMATIC S5) PLC
PLC & HMI

Siemens PLC Programming, S7-300 and S7-400 (SIMATIC S5) PLC

How to get data from plc to excel
PLC & HMI

How to get data from plc to excel

PLC Function Blog Diagram (FBD)
PLC & HMI

PLC Function Blog Diagram (FBD)

Next Post
Siemens TIA (Totally Integrated Automation) Portal

Siemens TIA (Totally Integrated Automation) Portal

Please login to join discussion

You might also like

PLC Controller Firmware Upgrade

PLC Controller Firmware Upgrade

Connect to PLC via USB cable

Connect to PLC via USB cable

PLC First Scan Bit

PLC First Scan Bit

Siemens PLC Programming, S7-300 and S7-400 (SIMATIC S5) PLC

Siemens PLC Programming, S7-300 and S7-400 (SIMATIC S5) PLC

How to get data from plc to excel

How to get data from plc to excel

PLC Function Blog Diagram (FBD)

PLC Function Blog Diagram (FBD)

PLC Programming & Automation

PLC Programming

The objectives of PLCtr are to provide practical instruction and help for anybody involved with PLCs from the maintenance staff to the PLC programmer. You don’t necessarily have to be a “writer” to contribute. If it has anything to do with any PLC and the devices connected to it then we are interested. If you want to become a writer, please write to us on the contact page. Join us.

Tags

Add-On Instruction alarm allen-bradley ALMA analog codes comminucation communication connect control controller ControlLogix cpu devicenet download driver EDS error errors ethernet example factorytalk fault Function instruction issue Ladder Major motor network plc problem program Programming rockwell rslinx rslogix siemens software start state stop Studio 5000 tag timer

Contact Us

PLC Programming

The objectives of PLCtr are to provide practical instruction and help for anybody involved with PLCs from the maintenance staff to the PLC programmer. You don’t necessarily have to be a “writer” to contribute. If it has anything to do with any PLC and the devices connected to it then we are interested. If you want to become a writer, please write to us on the contact page. Join us.

  • Home
  • PLC Forum
  • Contact Us
  • PLC & HMI
  • Electric & Electronic

© plctr.com PLC Programming | PLC Forum.

No Result
View All Result
  • Home
  • PLC Forum
  • Contact Us
  • PLC & HMI
  • Electric & Electronic

© plctr.com PLC Programming | PLC Forum.

We use cookies on our website to give you the most relevant experience by remembering your preferences and repeat visits. By clicking “Accept”, you consent to the use of ALL the cookies.
Cookie settingsACCEPT
Privacy & Cookies Policy

Privacy Overview

This website uses cookies to improve your experience while you navigate through the website. Out of these cookies, the cookies that are categorized as necessary are stored on your browser as they are essential for the working of basic functionalities of the website. We also use third-party cookies that help us analyze and understand how you use this website. These cookies will be stored in your browser only with your consent. You also have the option to opt-out of these cookies. But opting out of some of these cookies may have an effect on your browsing experience.
Necessary
Always Enabled

Necessary cookies are absolutely essential for the website to function properly. This category only includes cookies that ensures basic functionalities and security features of the website. These cookies do not store any personal information.

Non-necessary

Any cookies that may not be particularly necessary for the website to function and is used specifically to collect user personal data via analytics, ads, other embedded contents are termed as non-necessary cookies. It is mandatory to procure user consent prior to running these cookies on your website.