HMI
Start-Stop with HMI
What is start-stop with an HMI?
It is a PLC start-stop circuit with an operator panel (HMI, touch screen) added. The motor can be started and stopped from the buttons on the panel and from the buttons on the screen. The screen shows whether the motor is running and any overload fault.
Where is an HMI used?
Almost every modern machine has an operator panel. With an HMI the machine is started, settings are changed, and counts and faults are monitored. A single screen replaces dozens of buttons and lamps on the panel door.
PLC and HMI wiring
The HMI connects to the PLC through a communication cable and is supplied with 24 V DC. Buttons on the screen write to PLC memory bits, and indicators on the screen read PLC bits. The seal-in and safety are still done in the PLC program.
What to watch out for
Safety functions such as the emergency stop are not left to the screen; they are also done with physical buttons on the panel. The motor status on the screen should come from feedback that shows the contactor has really energized.
Parts used
Run it in the simulator.
This circuit is ready in the CoilPath library. Open it, press the buttons and follow the current. It also comes with a wiring view and a panel layout.