How-To
PLC How-To
PLC How-To in industrial control systems — covering 8 topic areas in the CurryControls.com controls and automation knowledge hub.
Written guides in this section
Full references, procedures, and diagnostic guides published under PLC How-To.
How to Build a Sequencer
Build a step sequencer in a controller that will not stick, restart into the wrong step, or leave equipment half way: define the steps from the narrative, choose a step register, and test every path before the plant depends on it.
9 min readUpdated Sep 5, 2026
How to Configure a Modbus Connection
Set up a Modbus RTU or TCP link between a controller and a device: get the register map, match the physical and protocol settings, build the reads and writes, handle data types and the addressing offset, and verify with a protocol tool before trusting a value.
10 min readUpdated Sep 5, 2026
How to Diagnose Read and Write Communications
Diagnose a controller that cannot read from or write to a device: capture the exact request and response, classify the failure as no link, no answer, or a rejected exchange, read the error or exception code, compare with a test tool, and fix the port.
8 min readUpdated Sep 5, 2026
How to Create a PID Loop in a PLC
Set up a PID instruction from scratch: scale the PV and CV, pick the action, set the execution rate, configure limits and anti-windup, tune conservatively, and test the manual and auto transitions before it controls anything.
10 min readUpdated Sep 5, 2026
How to Add an Alarm
From a request to a working alarm: define it against the philosophy, build the condition in the PLC with deadband and delays, configure the SCADA alarm with priority and message, test it end to end, and record it in the master alarm database.
9 min readUpdated Sep 5, 2026
How to Configure Remote I/O
Add a remote I/O rack to a controller over Ethernet: plan the network and addresses, set the adapter, and prove every point and the failure behavior before the rack goes into service.
8 min readUpdated Sep 5, 2026
Topics in this area
Scale a 4-20 mA Input
Turn raw analog counts into engineering units, with the arithmetic worked out.
Program Lead/Lag Pumps
Build duplex pump control with alternation, run-time balancing, and a failure fallback.
Build a Sequencer
Build a Sequencer — practical reference notes for controls engineers, integrators, and technicians working with plc how-to.
Configure Modbus
Set up a Modbus master and prove the poll is working.
Diagnose READ/WRITE Communications
Diagnose READ/WRITE Communications — practical reference notes for controls engineers, integrators, and technicians working with plc how-to.
Create a PID Loop
Create a PID Loop — practical reference notes for controls engineers, integrators, and technicians working with plc how-to.
Add an Alarm
Add an Alarm — practical reference notes for controls engineers, integrators, and technicians working with plc how-to.
Configure Remote I/O
Configure Remote I/O — practical reference notes for controls engineers, integrators, and technicians working with plc how-to.
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