Motor Starter Logic: Build a Fail-Safe System in 5 Rungs

Motor Starter Logic: Build a Fail-Safe System in 5 Rungs

Start, stop, overload. Almost every motor in a plant is controlled by those three signals, and almost every PLC programmer writes the rung that ties them together in their first week. This is the motor starter ladder logic. It is also where a surprising number of real faults come from: a stop button examined with … Read more

TON, TOF, or RTO? Which PLC Timer Should You Use?

TON, TOF, or RTO? Which PLC Timer Should You Use?

Almost every PLC program you will ever write has a timer in it. PLC timers will sound a horn before a motor starts. A fan keeps running after a heater shuts off. A pump counts its running hours until it is due for service. Those three jobs need three different timers: TON, TOF and RTO. … Read more