Time instructions in our productivity blocks programming (Arduino sketches) consist of runtime (ms), runtime (us), delay ms, and delay microseconds us.
We will be looking at each of these instructions that are available for our program using productivity blocks. Delay instructions in our sketches should be used with caution. They will pause our program for the delayed time, not allowing other parts of the program to function. We will be looking at this and the method to do the exact same delay functions without pausing your program.
A sample program will be discussed to demonstrate the time functions in our program. Let’s get started. Continue Reading!
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!
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 Instructions – Video)
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!
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!
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!
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!
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!
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.
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 Software – Video
Establish Communication – Video
Numbering System and Addressing – Video
The programming software and manuals can be downloaded from the Automation Direct website free of charge. Keep on Reading!
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:
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:
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
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.
1 – Input / Ouput ON
0 – Input / Output OFF
x – Input / Output Does not Matter
When the 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.
Control of the Motor (Conveyor) and the paint spray is done with the V0:0 contacts 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.
Test the program:
Watch on YouTube: PLC Programming Example – Paint Spraying
If you have any questions or need further information please contact me.
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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