Case for ESP32-Modbus-Gateway (FreeCAD)

The Gateway

To connect a Photovoltaic inverter to a SmartHome-environment the Github user @TobiasFaust developed the great project SolaxModbusGateway - big thanks to him!

His Gateway is composed of a ESP32-board and a RS485 interface-board. The ESP32 is connected via the RS485-interface to the inverter and on that way the ESP sends commands to read values out of the inverter. The ESP32 converts the values and sends them over WiFi to a MQTT-server of the SmartHome. Maintenance of the Gateway can be done via a Web-interface.

The Case

The Gateway is built of a ESP32 Board Dev Kit C V4 from AZ-delivery and a interface-board XY-K485 TTL-to-RS485 Serial Port Converter module.

To run the Gateway in the cellar (where the inverter resides) I created a compact Case to hold the two modules.

It has openings to supply the ESP32 via USB and to connect the Modbus-wires to its screw-terminals on the interface-board. I designed two openings to look at the RX- and TX-LEDs of the interface to observe the communication.

I have designed Case-options to install an external antenna at the front or top of the Case and to have a hook to fasten the Modbus-cable with a cable-tie.

The Case-design needs only one screw and one heat-insert, the prints are snapped in or held in place by the top-lid.

Besides the STLs I published my FreeCAD-file here so you can modify the Case or build something new on base of this. In the CAD-file you find the housing, the lids and additional mockups of the ESP32-board and the RS485-board. There is a built-in spreadsheet holding parameters to modify the model like e.g. wall-thickness of the housing. In the parameters you can switch between front- and top-antenna. To get the housing without cable-holder, go back in the design-tree to the point before the holder-design starts and export the STL there.

Building

Needed materials for the Case are

• one heat-insert Ruthex M3s for the lid
• one M3x6 screw
• a little bit paint to lay out the labelings if you like

All parts of the Case were printed from Eryone PLA black on my Anycubic SonicVyper, 0,4mm nozzle, LH 0,2mm, LW 0,4mm. All parts can be printed without supports - all overhangs are done at a printable angle.

On the top of the case the RS485-connector and the LEDs have labelings, done by engraved letters. You may lay out the engravings with white paint (in a black case) - they show up nicely.

Unfortunatly my first-layer of the print was not optimized - so I had too much material on the first layers and didn‘t get a clean engraving. On another print it worked and showed up nicely …but I didn‘t take pictures to show here.