The exact procedure will depend on the manufacturer and model of the controller, so always consult the device’s manual. Generally:
Power cycle / Soft Reset: The simplest reset is often just power cycling the device (turning it off and on). Some controllers have a dedicated reset pin or button that triggers a reboot without removing power. This type of reset re-initializes the controller but does not erase the configuration. For example, many PLCs have a small recessed reset button you can press to restart the CPU. This helps recover from a freeze or to get the controller to re-run its startup routine.
Factory Reset (Restore defaults): To fully reset all settings to factory defaults, controllers often require a specific button sequence or jumper setting. For instance, a device might require holding down a reset button for more than 5 seconds, or pressing a tiny “INIT” switch while powering on, etc. As an example, one Gantner Instruments controller requires tapping the reset button, then holding it for 5 seconds, then releasing and tapping again, to clear all settings. This kind of reset wipes user configurations and returns the device to default IP addresses, cleared memory, default passwords, and so on. Always follow the exact instructions – the timing and sequence can be important.
Reset via Software: Some controllers can be reset remotely through software commands or their web interface. For example, issuing a “factory reset” command over a console or using the vendor’s configuration software to send a reset instruction. Ensure that you have saved any needed configurations, as factory resets cannot be undone.
After Reset: Once a controller is reset, you may need to reconnect and reconfigure it. If it’s a networked device, it might revert to a default IP or hostname. If it’s a PLC, it might clear the program from memory (unless it’s stored in non-volatile memory separately). Consult the manual to understand what is cleared by a factory reset (e.g., user program, communication settings, I/O calibration, etc.).
In summary, resetting a controller typically involves either pressing a hardware reset button or performing a specific power-on sequence. For a simple reboot, a quick press or power cycle suffices; for a deep reset to defaults, a longer press or special procedure is used. Always ensure you have backed up configurations and understand the reset procedure from the manufacturer’s documentation to avoid unintended data loss.