Category Archives: Timers

On delay, off delay, interval, timing charts are discussed.

PLC Fiddle Timer Challenge

Timers are present in just about every PLC program that I have seen. 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 secret to using timers is a good review of using these timing charts.

PLC Fiddle has three different timing instructions for us to use in our programs. On-Delay, Off-Delay and Retentive Timers. We will discuss the timer parameters and the three different instructions. Our timer challenges will help you gain a good understanding of how timers work in the PLC. Let’s get started. Continue Reading!

Productivity 1000 Series PLC Timer Instructions

Just about every programmable logic controller (PLC) program will include a timer instruction. The Productivity 1000 Series PLC has several different timer instructions for your program. We discussed the timed coil (TMC) and flasher coil (FLS) last time as part of the contacts and coil discussion. (Contact and Coil InstructionsVideo)

We will now look at using the Simple Timer (STMR) and the Timer (TMR) instructions in the productivity suite software. Let’s get started. Continue Reading!

BRX PLC Timers

A majority of the programmable logic controller (PLC) programs will include a timer instruction. The BRX series of programmable logic controllers have several different timers available for your program. There are nine different basic timing instructions in the PLC. The memory area for timers, include the Timer PVs (Present Values) Timer SVs (Set Values) and the Timer Completion Flags. The default size of the timer area is T0 – T255. This size can change to the amount that we need for our program. Please see BRX PLC Numbering Systems and Addressing on how to change the memory configuration of the controller.
We will be looking at the timer instructions in the BRX PLC along with some programming examples. As a system integrator, this ability can prove very useful to you in the field when commissioning your automation system. When dealing with timers, we need to look at timing charts. The Secret of Using Timers is a good refresher on using timing charts.
Let’s get started with the BRX PLC Timers. Continue Reading!

Omron CP1H Timers

The Omron CP1H series of programmable logic controllers are capable of having 4096 timers. There are twelve different timing instructions in the PLC. Six binary and six BCD instructions for the set values of the timers separate the six basic instructions. The memory area for timers have separate areas for the Timer PVs (Present values) and the Timer Completion Flags. We will be looking at the timer instructions in the CP1H along with some programming examples. Continue Reading!

Horner XL4 Timers and Counters

Timers and counters are used in the majority of PLC programs. We will not look at how timers and counters can be programmed in the Horner XL4 OCS all-in-one controller. Continue Reading!

Click PLC Drum Instruction

Drum instructions are great tools when you have a simple sequence of events that need to occur at a set time interval or as a result of an event. They mimic an electromechanically drum sequencer. The Click PLC has a drum in the instruction set. We will discuss the drum instruction and look at an example of controlling traffic lights.  Keep on Reading!

PLC Programming Example – Delay Starting of 7 Motors

We will look at a PLC programming example of delaying the start of 7 motors. Each motor will be on a switch that the operator can select at any time. The motor outputs should have a 5 second delay between the outputs coming on.

This question originally came from PLCTalk.net. An original solution to the problem came from Peter Steinhoff. His solution is what we will be presenting. It is simple and straight forward.

We will be using the Do-more Designer software which comes with a simulator. This fully functional program is offered free of charge at automation directKeep on Reading!

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:
System Hardware – Video
Installing the SoftwareVideo
Establish CommunicationVideo
Numbering System and AddressingVideo
The programming software and manuals can be downloaded from the Automation Direct website free of charge.  Keep on Reading!

PLC Programming Example – Paint Spraying

We will look at a PLC basic tutorial of a paint spraying station. Following the 5 steps to program development this PLC programming example should fully explain the procedure for developing the PLC program logic. Ladder will be our PLC programming language.

We will be using the Do-more Designer software which comes with a simulator. This fully functional program is offered free of charge at automation direct.

Define the task:

What has to happen?
Paint Station 01

Paint spraying system where boxes are fed by gravity through a feeder magazine one at a time onto a moving conveyor belt. Upon the start signal, boxes are pushed towards the conveyor by valve 1. This is a cylinder which extends and retracts which operates switches S1 and S2 respectfully. A spraying nozzle paints each box as it passes under the paint spray controlled by valve 2. A sensor (S3) counts each box being sprayed. When 6 boxes have been painted the valve 2 shuts off (paint spray) and valve 1 (cylinder) stops moving boxes onto the conveyor. Three seconds later the conveyor stops moving and the hopper with its load moves forward (valve 3) where it is emptied. Ten seconds later the hopper returns to the original position. The cycle is then complete and waits for a start signal again.

Define the Inputs and Outputs:

Inputs:
Start Switch – On/Off (Normally Open) – NO
Stop Switch – On/Off (Normally Closed) – NC
S1 – Valve 1 (cylinder retract) On/Off – NO
S2 – Valve 1 (cylinder extend) On/Off – NO
S3 – Box Detected- On/Off – NO
Outputs:
Motor – On/Off (Conveyor Run)
Valve 1- Cylinder to feed boxes – On/Off
Valve 2- Paint Spray – On/Off
Valve 3- Cylinder to move hopper – On/Off

Develop a logical sequence of operation:

Fully understanding the logic before starting to program can save you time and frustration.

Sequence Table: The following is a sequence table for our paint spraying application.

Sequence Table
1 – Input / Ouput ON
0 – Input / Output OFF
x – Input / Output Does not Matter
When power goes off and comes on the sequence will continue. This means that we must use memory retentive areas of the PLC. The stop pushbutton will stop the sequence. The start will resume until the end.

Develop the PLC program:

The best way to see the development of the programmable logic controller program is to follow the sequence table along with the following program. You will see the direct correlation between the two and get a good understanding of the process.

This is the main process start and stop bit. V0:0 is used because it is memory retentive.
Paint Stn Program 1

Control of the Motor (Conveyor) and the paint spray is done with the V0:0 contact in front of the actual PLC output. The conveyor and paint spray will stop when the timer 0 is done. This is the delay after the last box is detected to allow the box to be painted and loaded onto the hopper.
Paint Stn Program 2

Control of the box movement onto the conveyor. As long as we have the process start and the hopper count is not complete this will allow the cylinder to put boxes on the conveyor.
Paint Stn Program 3

Count number of boxes in the hopper via S3. The counter is memory retentive.
Paint Stn Program 4

Timer to stop the conveyor and spray after the last box is detected for the hopper. This will allow time for the box to be sprayed and loaded into the hopper.
Paint Stn Program 5

Hopper movement to load and unload the boxes.
Paint Stn Program 6

The hopper unload timer is to unload the boxes and will then trigger the reset conveyor timer, box counter and the process start bit (V0:0).
Paint Stn Program 7

Test the program:

Paint Spraying
Test the program with a simulator or actual machine. Make modifications as necessary. Remember to follow up after a time frame to see if any problems arise that need to be addressed with the program.

Watch on YouTube : PLC Programming Example – Paint Spraying
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.

To get this free article, subscribe to my free email newsletter.


Use the information to inform other people how numbering systems work. Sign up now.

The ‘Robust Data Logging for Free’ eBook is also available as a free download. The link is included when you subscribe to ACC Automation.




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.

To get this free article, subscribe to my free email newsletter.


Use the information to inform other people how numbering systems work. Sign up now.

The ‘Robust Data Logging for Free’ eBook is also available as a free download. The link is included when you subscribe to ACC Automation.