Contacts and Coils in PLC Ladder Logic
The most elementary objects in Ladder Diagram programming are contacts and coils, intended to mimic the contacts and coils of
Motor Trip Logic using PLC Programming
Programmable Logic Controller (PLC) Questions and Answers This PLC is being used to start and stop an electric motor, and
PLC Program for Motor Starter
PLC tutorial explaining step by step procedure to program PLC for motor starter. Motor starters are of many types however
PLC Pump Permissive Interlocks
The following PLC program was written to control the operation of a large electric motor-driven pump. A variety of “permissive”
What is Ladder Diagram Programming ?
Ladder Diagram (LD) Programming The most common language used to program PLCs is Ladder Diagram (LD), also known as Relay
Basics of Fail-safe Circuits
Logic circuits, whether comprised of electromechanical relays or solid-state gates, can be built in many different ways to perform the
History of Programmable Logic Controllers (PLC)
Every control system may be divided into three general sections: input devices (sensors), controllers, and output devices (actuators). The input
PLC Electric Motor Interlocks
Programmable Logic Controller Questions and Answers The following PLC program was written to control the operation of a large electric
PLC Data Comparison Instructions
As we have seen with counter and timers, some PLC instructions generate digital values other than simple Boolean (on/off) signals.
PLC Math instructions
The IEC 61131-3 standard specifies several dedicated ladder instructions for performing arithmetic calculations. Some of them are shown here: PLC