In the previous post, we covered the basic PLC timer instructions:
TON = Timer On Delay
TOF = Timer Off Delay
RTO = Retentive Timer On
Now we are going one step deeper.
In real …
Read MoreIn industrial automation, PLC counters are used when a machine needs to count events.
A counter can count:
Parts
Boxes
Bottles
Cycles
Machine strokes
Rejects
Pallets
Sensor pulses
Production totals
A counter does not count time.A counter counts how many times …
Read MoreIn the previous post, we covered standard PLC counters such as:
CTU = Count Up
CTD = Count Down
CTUD = Count Up / Count Down
Those counters work well for many basic counting …
Read MoreIn PLC programming, not every instruction directly turns on a motor, counts a box, or starts a timer.
Some instructions are used to control how the PLC program executes.
These are called …
Read MoreIn PLC troubleshooting, one of the most powerful and dangerous tools is forcing.
A PLC force allows a technician or programmer to manually override the normal state of an input or …
Read MoreIn PLC programming, not all logic is simple ON/OFF control.
Sometimes the PLC needs to work with numbers.
The PLC may need to:
Move a value from one tag to another
Compare a process …
In industrial automation, a PLC panel can have a perfect program and still behave incorrectly if the electrical installation has noise or grounding problems.
Electrical noise can cause problems such as:
Random …
Read MorePLC troubleshooting is not about guessing which part is bad.
A good Automation Technician follows a method.
When a machine does not run, the problem could be in many places:
Field device
Sensor wiring
24 …
PLC input problems are very common in industrial automation.
A machine may stop, refuse to start, stay stuck in a sequence, or show an HMI alarm because the PLC is not …
Read MorePLC Communication Basics
Modern PLC systems rarely work alone.
A PLC may communicate with:
HMI panels
VFDs
Remote I/O
Servo drives
Robots
Barcode readers
Vision systems
SCADA computers
Industrial switches
Other PLCs
Data collection systems
In older systems, many signals were hardwired point-to-point.
Example:
PLC output …
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