HomeMaster MiniPLC Puts ESPHome on a 9-Module DIN Rail

There is a persistent gap in home automation hardware between a hobby board taped inside a junction box and a proper industrial controller that costs more than the appliances it switches. The HomeMaster MiniPLC, detailed by CNX Software on August 26, 2026, aims straight at that gap: an ESP32-based DIN-rail controller with real isolated industrial I/O, ESPHome preinstalled, and open hardware licensing.

• Built around an ESP32-WROOM-32D-N16 module with a dual-core 240MHz processor, 520KB of SRAM and 16MB of flash
• Industrial I/O includes 6 relay outputs rated 3A at 250V AC, 4 isolated 24V digital inputs, 4 analog inputs at 16-bit resolution and a 12-bit analog output
• Ships with ESPHome preinstalled and is recognised as Made for ESPHome by the Open Home Foundation, integrating with Home Assistant over the local network
• Priced at $324 on Tindie, occupying 9 DIN modules at 157.4 x 91 x 58.4mm, powered from 24V DC or 85 to 265V AC

What Makes This Different From an ESP32 in a Project Box

The specification list is where the industrial intent shows. Alongside the relays and digital inputs sit two PT100 and PT1000 RTD channels for precision temperature sensing, two one-wire buses, and an RS-485 port speaking Modbus RTU. That last one is the quiet headline: RS-485 Modbus is the lingua franca of building equipment, so the MiniPLC can talk to heat pumps, energy meters, ventilation units and inverters that have no idea what a smart home is.

The front panel is equally practical. A 128x64 OLED display, four buttons, twelve status LEDs and a buzzer mean the controller remains diagnosable when the network is down, which is exactly when you need it. There is a microSD slot and a battery-backed real-time clock for local logging and scheduling.

Why Does ESPHome Preinstallation Matter?

Because it removes the single largest failure point in DIY building control: the custom firmware nobody else can maintain. ESPHome configurations are declarative YAML, version-controllable, and readable by anyone who inherits the installation. The Open Home Foundation's Made for ESPHome recognition means the device ships with a working configuration rather than a promise of one, and adoption into Home Assistant is a discovery step rather than an integration project.

The openness goes further than firmware. The hardware is released under CERN-OHL-W v2 and the firmware under MIT, with documentation on GitHub. For anyone who has watched a proprietary controller become e-waste when its cloud service retired, a locally-controlled device with published schematics is worth a meaningful premium. It is the same argument behind projects like the ESP32-S31 Linux BSP preview we covered last week.

The Honest Limits Before You Order

The maker is refreshingly direct about the constraints, and they are worth reading before the wiring diagram. This is an indoor-only device rated 0C to +40C. The relays top out at 3A, so heavier loads need external contactors, which is normal practice but adds panel width. Enabling the RTD inputs disables USB serial logging because the GPIO pins are shared. Ethernet is optional rather than standard, and at the time of writing Tindie shipping is limited to the EU.

At $324 the MiniPLC is not competing with a $12 development board. It is competing with a commercial building controller plus a gateway plus a licence, and on that comparison the value is clear. It also fits a broader pattern of Linux and microcontroller hardware moving into panel-mount formats, alongside boards like the Luckfox Lyra PLC we covered earlier this month. More single board computer and home automation hardware is on our mini computers page.

Sources: CNX Software — August 26, 2026; HomeMaster on Tindie — August 2026; Open Home Foundation ESPHome — August 2026.