Tag Archives: automation direct plc

Click PLC Timers and Counters

Continuing our series, we will now look at timers and counters and how they are used in the Click PLC. Previously we have discussed:
Click PLC System Hardware
Click PLC Installing the Software
Click PLC Establish Communication
Click PLC Numbering System and Addressing
The programming software and manuals can be downloaded from the Automation Direct website free of charge.  Keep on Reading!

Click PLC Numbering System and Addressing

Continuing our series, we will now look at the numbering systems and addressing used in the Click PLC. Previously we have discussed:
Click PLC System Hardware
Click PLC Installing the Software
Click PLC Establish Communication
The programming software and manuals can be downloaded from the Automation Direct website free of charge. These are being used exclusively in our Click PLC series.  Keep on Reading!

Click PLC Establish Communication

So far in this series we have discussed the Click PLC System Hardware and Installed the Software. Today we will be establishing PC to PLC communications. This will allow us to program, edit or alter the way in which our Click PLC will function.  Keep on Reading!

Click PLC Installing the Software

Previously we discussed the Click PLC System Hardware. Today we will be installing the free software required to program the PLC. This includes the actual program and communication drivers.  Keep on Reading!

Click PLC System Hardware

Many people ask me what I do when looking at a new PLC model or system. My approach is very straight forward and we will view this in action with this Click PLC series. This series will go from examining the hardware to programming and communicating to the PLC in several ways. If you have questions along the way, please let me know. Keep on Reading!

The Secret of Using Timers

Timers are used in the majority of PLC programs. There are also a wide variety of off the shelf industrial timers that you can use. The implementation of timers can be vast, however it all starts with a TIMING CHART.

A timing chart is the secret behind understanding of the timer that you need in your application. Making a timing chart before writing the program will ensure that all of the information will be accounted.

The timing chart is mapped out on a x and y plain. The ‘y’ plain has the state of the input on/off (1 or 0). The ‘x’ plain will show time.

Lets take a look at a timing chart for an On-Delay Timer. This is the basic operation for an Omron H3BR industrial timer.

Timing Chart On-Delay Basic

Power –  When dealing with PLC’s we must consider when power to the unit is removed what happens to the current time and output conditions.
Start – In this case the start signal is momentary to start the time cycle. (t) We could modify this signal to be maintained until the output switches.
Output – The output will show when it turns on. This can also indicate the opposite, and show when it turns off.
Time – Time is shown by the relationship between the start signal and the output. Our example shows timing starts on the leading edge of the Start. This could have also been on the trailing edge.

Here is the same on-delay timing chart with some more detail. Several conditions are added to the chart.

Timing Chart On-Delay Details

These conditions prompt us to ask the following questions.
What happens when:

  • Power is removed / restored
  • Multiple start signals are received
  • Do we need a Reset signal. If so what happens during its operation
  • Do we need a display of the time. Present Value (PV) / Set Value (SV)

As you can see the timing chart is vital in determining how the sequence will be performed. This is the exact same method that I use when determining timing sequences in a PLC program.

Lets look at an example.

Motor_Sequence

When we hit the start button, the warning light then comes on. After a fixed time the warning light goes off and the motor starts. The motor will run until the stop button is hit.

We will start by using the Start / Stop Circuit we did earlier.

Timer Program

You will notice that we have added an internal memory bit (C0) as our Start Sequence. This is a memory retentive bit, so we can use the (ST0) $FirstScan to make this circuit non-memory retentive. If power goes off, or the PLC is put into program mode the circuit does not remember the last state. It will default to be off.
The sequence is as follows:

  • Start pressed
  • TMR starts to time (10seconds)
  • Warning output comes on
  • After TMR (10seconds)
    • Warning output goes off
    • Motor output comes on
  • Stop pressed
    • TMR is reset to 0
    • Warning light off
    • Motor is off

Every PLC has timers. They all have different types depending on what you are trying to achieve. It will all start with your Timing Chart.

Watch on YouTube : Learn PLC Programming – Free 8 – The Secret of Timers

If you have any questions or need further information please contact me.
Thank you,
Garry



If you’re like most of my readers, you’re committed to learning about technology. Numbering systems used in PLC’s are not difficult to learn and understand. We will walk through the numbering systems used in PLCs. This includes Bits, Decimal, Hexadecimal, ASCII and Floating Point.

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