AppBlocks vs. a PLC
PLCs run the world’s machines, and nothing here changes that. But many jobs that end up on a PLC are really monitoring, alarming, and simple control at a site that needs to be online. For those, a connected controller built with AppBlocks is often simpler, from the first wire to the hundredth site.
Getting a small, connected control job online
How a typical PLC setup compares with AppBlocks when the job needs connectivity, remote access, and a simple local interface.
This table covers connected-device features. For safety, deterministic control, and large I/O counts, see where the PLC is the better choice below.
Most plants need both.
The common setup is a PLC for control and an AppBlocks device next to it for data, alarms, and remote access.
Choose AppBlocks when…
- The job is monitoring, alarming, or simple on/off and setpoint control
- The site needs MQTT, cloud dashboards, SMS alarms, or remote setpoints
- You’re rolling the same controller out to many small sites
- You need a gateway that gets existing PLC data out over Modbus
- You’d like the logic to be readable by people who don’t program PLCs
Keep the PLC when…
- The application includes safety functions, E-stops, or needs a SIL or PL rating
- You need a deterministic scan cycle for fast machine or motion control
- The panel has a large I/O count, or needs PROFINET, EtherNet/IP, or another fieldbus
- Plant standards or your customer specify a PLC platform
- The maintenance team needs to troubleshoot online in the vendor IDE
Questions, answered.
Can AppBlocks replace a PLC?
For simple, non-safety control at connected sites, often yes: pumps on levels, fans on schedules, and cold rooms on thermostats. For machine control, motion, and safety functions, keep the PLC and use AppBlocks alongside it.
Is AppBlocks deterministic like a PLC scan cycle?
No. AppBlocks apps are event-driven on the Zephyr RTOS: flows run when inputs change, timers complete, or messages arrive. That suits monitoring and supervisory control, not high-speed or safety-critical control.
Can an AppBlocks device work with my existing PLC?
Yes. It can poll the PLC over Modbus RTU or TCP and forward the data to MQTT or the cloud, or act as a Modbus slave that the PLC reads as remote I/O. PLC to MQTT gateway.
I program PLCs. How long does it take to learn AppBlocks?
Most of what you know carries over. Contacts, coils, timers, counters, and compares all have matching blocks; the main change is thinking in events instead of scans. Ladder logic to flowcharts.
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